  
  [1X54 [33X[0;0YPartial permutations[133X[101X
  
  [33X[0;0YThis chapter describes the functions in [5XGAP[105X for partial permutations.[133X
  
  [33X[0;0YA [13Xpartial permutation[113X in [5XGAP[105X is simply an injective function from any finite
  set  of  positive integers to any other finite set of positive integers. The
  largest point on which a partial permutation can be defined, and the largest
  value  that  the  image  of  such  a  point can have, are defined by certain
  architecture dependent limits.[133X
  
  [33X[0;0YEvery  inverse  semigroup  is  isomorphic to an inverse semigroup of partial
  permutations  and,  as  such,  partial permutations are to inverse semigroup
  theory  what  permutations  are  to  group theory and transformations are to
  semigroup  theory.  In  this  way,  partial permutations are the elements of
  inverse partial permutation semigroups.[133X
  
  [33X[0;0YA  partial  permutations in [5XGAP[105X acts on a finite set of positive integers on
  the right. The image of a point [10Xi[110X under a partial permutation [10Xf[110X is expressed
  as  [10Xi^f[110X  in  [5XGAP[105X.  This  action is also implemented by the function [2XOnPoints[102X
  ([14X41.2-1[114X).  The  preimage of a point [10Xi[110X under the partial permutation [10Xf[110X can be
  computed   using   [10Xi/f[110X  without  constructing  the  inverse  of  [10Xf[110X.  Partial
  permutations  in  [5XGAP[105X  are created using the operations described in Section
  [14X54.2[114X. Partial permutations are, by default, displayed in component notation,
  which is described in Section [14X54.6[114X.[133X
  
  [33X[0;0YThe fundamental attributes of a partial permutation are:[133X
  
  [8XDomain[108X
        [33X[0;6YThe  [13Xdomain[113X  of  a  partial  permutation  is  just the set of positive
        integers  where  it  is  defined; see [2XDomainOfPartialPerm[102X ([14X54.3-4[114X). We
        will denote the domain of a partial permutation [10Xf[110X by dom([10Xf[110X).[133X
  
  [8XDegree[108X
        [33X[0;6YThe  [13Xdegree[113X  of  a  partial permutation [10Xf[110X is just the largest positive
        integer  where  [10Xf[110X  is  defined. In other words, the degree of [10Xf[110X is the
        largest element in the domain of [10Xf[110X; see [2XDegreeOfPartialPerm[102X ([14X54.3-1[114X).[133X
  
  [8XImage list[108X
        [33X[0;6YThe  [13Ximage  list[113X of a partial permutation [10Xf[110X is the list [10X[i_1^f, i_2^f,
        ..  ,  i_n^f][110X  where  the  domain  of  [10Xf[110X  is  [10X[i_1,  i_2, .., i_n][110X see
        [2XImageListOfPartialPerm[102X ([14X54.3-6[114X). For example, the partial perm sending
        [10X1[110X to [10X5[110X and [10X2[110X to [10X4[110X has image list [10X[ 5, 4 ][110X.[133X
  
  [8XImage set[108X
        [33X[0;6YThe  [13Ximage set[113X of a partial permutation [10Xf[110X is just the set of points in
        the  image  list  (i.e.  the  image list after it has been sorted into
        increasing  order); see [2XImageSetOfPartialPerm[102X ([14X54.3-7[114X). We will denote
        the image set of a partial permutation [10Xf[110X by im([10Xf[110X).[133X
  
  [8XCodegree[108X
        [33X[0;6YThe  [13Xcodegree[113X  of a partial permutation [10Xf[110X is just the largest positive
        integer  of the form [10Xi^f[110X for any [10Xi[110X in the domain of [10Xf[110X. In other words,
        the  codegree  of  [10Xf[110X  is  the  largest  element in the image of [10Xf[110X; see
        [2XCodegreeOfPartialPerm[102X ([14X54.3-2[114X).[133X
  
  [8XRank[108X
        [33X[0;6YThe  [13Xrank[113X  of  a  partial  permutation [10Xf[110X is the size of its domain, or
        equivalently   the   size   of  its  image  set  or  image  list;  see
        [2XRankOfPartialPerm[102X ([14X54.3-3[114X).[133X
  
  [33X[0;0YA  [13Xfunctional  digraph[113X is a directed graph where every vertex has out-degree
  [10X1[110X.  A  partial  permutation [3Xf[103X can be thought of as a functional digraph with
  vertices  [10X[1..DegreeOfPartialPerm(f)][110X and edges from [10Xi[110X to [10Xi^f[110X for every [10Xi[110X. A
  [13Xcomponent[113X  of  a  partial  permutation  is  defined  as  a  component of the
  corresponding functional digraph. More specifically, [10Xi[110X and [10Xj[110X are in the same
  component  if  and only if there are [22Xi=v_0, v_1, ..., v_n=j[122X such that either
  [22Xv_k+1=v_k^f[122X or [22Xv_k=v_k+1^f[122X for all [10Xk[110X.[133X
  
  [33X[0;0YIf  [10XS[110X  is  a semigroup and [10Xs[110X is an element of [10XS[110X, then an element [10Xt[110X in [10XS[110X is a
  [13Xsemigroup   inverse[113X  for  [10Xs[110X  if  [10Xs*t*s=s[110X  and  [10Xt*s*t=t[110X;  see,  for  example,
  [2XInverseOfTransformation[102X  ([14X53.5-13[114X). A semigroup in which every element has a
  unique semigroup inverse is called an [13Xinverse semigroup[113X.[133X
  
  [33X[0;0YEvery  partial  permutation  belongs  to  a  symmetric  inverse  monoid; see
  [2XSymmetricInverseSemigroup[102X    ([14X54.7-3[114X).   Inverse   semigroups   of   partial
  permutations  are  hence  inverse  subsemigroups  of  the  symmetric inverse
  monoids.[133X
  
  [33X[0;0YThe  inverse  [10Xf^-1[110X  of  a  partial  permutation  [10Xf[110X  is  simply  the  partial
  permutation  that maps [10Xi^f[110X to [10Xi[110X for all [10Xi[110X in the image of [10Xf[110X. It follows that
  the  domain  of [10Xf^-1[110X equals the image of [10Xf[110X and that the image of [10Xf^-1[110X equals
  the domain of [10Xf[110X. The inverse [10Xf^-1[110X is the unique partial permutation with the
  property  that  [10Xf*f^-1*f=f[110X and [10Xf^-1*f*f^-1=f^-1[110X. In other words, [10Xf^-1[110X is the
  unique semigroup inverse of [10Xf[110X in the symmetric inverse monoid.[133X
  
  [33X[0;0YIf  [10Xf[110X  and  [10Xg[110X  are  partial  permutations,  then the domain and image of the
  product are:[133X
  
  
        [33X[1;6Y[24X[33X[0;0Ydom(fg)=(im(f)\cap dom(g))f^-1 and im(fg)=(im(f)\cap dom(g))g[133X [124X[133X
  
  
  [33X[0;0YA  partial  permutation  is  an idempotent if and only if it is the identity
  function on its domain. The products [10Xf*f^-1[110X and [10Xf^-1*f[110X are just the identity
  functions on the domain and image of [10Xf[110X, respectively. It follows that [10Xf*f^-1[110X
  is a left identity for [10Xf[110X and [10Xf^-1*f[110X is a right identity. These products will
  be referred to here as the [13Xleft one[113X and [13Xright one[113X of the partial permutation
  [10Xf[110X;  see  [2XLeftOne[102X  ([14X54.3-21[114X).  The  [13Xone[113X  of a partial permutation is just the
  identity on the union of its domain and its image, and the [13Xzero[113X of a partial
  permutation  is  just  the  empty partial permutation; see [2XOne[102X ([14X54.3-22[114X) and
  [2XZero[102X ([14X54.3-23[114X).[133X
  
  [33X[0;0YIf  [10XS[110X  is  an arbitrary inverse semigroup, the [13Xnatural partial order[113X on [10XS[110X is
  defined  as follows: for elements [10Xx[110X and [10Xy[110X of [10XS[110X we say [10Xx[110X[22X≤[122X[10Xy[110X if there exists an
  idempotent  element  [10Xe[110X  in [10XS[110X such that [10Xx=ey[110X. In the context of the symmetric
  inverse  monoid,  a partial permutation [10Xf[110X is less than or equal to a partial
  permutation [10Xg[110X in the natural partial order if and only if [10Xf[110X is a restriction
  of [10Xg[110X. The natural partial order is a meet semilattice, in other words, every
  pair  of  elements  has  a  greatest  lower  bound;  see  [2XMeetOfPartialPerms[102X
  ([14X54.2-5[114X).[133X
  
  [33X[0;0YNote  that  unlike permutations, partial permutations do not fix unspecified
  points  but  are simply undefined on such points; see Chapter [14X42[114X. Similar to
  permutations, and unlike transformations, it is possible to multiply any two
  partial permutations in [5XGAP[105X.[133X
  
  [33X[0;0YInternally,  [5XGAP[105X  stores a partial permutation [10Xf[110X as a list consisting of the
  codegree of [10Xf[110X and the images [10Xi^f[110X of the points [10Xi[110X that are less than or equal
  to the degree of [10Xf[110X; the value [10X0[110X is stored where [10Xi^f[110X is undefined. The domain
  and image set of [10Xf[110X are also stored after either of these values is computed.
  When  the  codegree  of  a  partial  permutation  [10Xf[110X  is less than 65536, the
  codegree  and images [10Xi^f[110X are stored as 16-bit integers, the domain and image
  set  are  subobjects  of  [10Xf[110X which are immutable plain lists of [5XGAP[105X integers.
  When  the  codegree of [10Xf[110X is greater than or equal to 65536, the codegree and
  images are stored as 32-bit integers; the domain and image set are stored in
  the  same  way as before. A partial permutation belongs to [10XIsPPerm2Rep[110X if it
  is stored using 16-bit integers and to [10XIsPPerm4Rep[110X otherwise.[133X
  
  [33X[0;0YIn  the  names of the [5XGAP[105X functions that deal with partial permutations, the
  word  [21XPermutation[121X  is  usually  abbreviated  to  [21XPerm[121X,  to  save typing. For
  example,   the   category   test   function   for  partial  permutations  is
  [2XIsPartialPerm[102X ([14X54.1-1[114X).[133X
  
  
  [1X54.1 [33X[0;0YThe family and categories of partial permutations[133X[101X
  
  [1X54.1-1 IsPartialPerm[101X
  
  [29X[2XIsPartialPerm[102X( [3Xobj[103X ) [32X Category
  [6XReturns:[106X  [33X[0;10Y[9Xtrue[109X or [9Xfalse[109X.[133X
  
  [33X[0;0YEvery  partial  permutation  in  [5XGAP[105X  belongs to the category [10XIsPartialPerm[110X.
  Basic  operations for partial permutations are [2XDomainOfPartialPerm[102X ([14X54.3-4[114X),
  [2XImageListOfPartialPerm[102X     ([14X54.3-6[114X),     [2XImageSetOfPartialPerm[102X     ([14X54.3-7[114X),
  [2XRankOfPartialPerm[102X  ([14X54.3-3[114X), [2XDegreeOfPartialPerm[102X ([14X54.3-1[114X), multiplication of
  two  partial  permutations  is  via  [9X*[109X,  and  exponentiation  with the first
  argument  a  positive  integer [10Xi[110X and second argument a partial permutation [10Xf[110X
  where  the  result is the image [10Xi^f[110X of the point [10Xi[110X under [10Xf[110X. The inverse of a
  partial permutation [10Xf[110X can be obtains using [10Xf^-1[110X.[133X
  
  [1X54.1-2 IsPartialPermCollection[101X
  
  [29X[2XIsPartialPermCollection[102X( [3Xobj[103X ) [32X Category
  
  [33X[0;0YEvery   collection   of   partial   permutations  belongs  to  the  category
  [10XIsPartialPermCollection[110X.  For  example,  a semigroup of partial permutations
  belongs in [10XIsPartialPermCollection[110X.[133X
  
  [1X54.1-3 PartialPermFamily[101X
  
  [29X[2XPartialPermFamily[102X[32X family
  
  [33X[0;0YThe family of all partial permutations is [10XPartialPermFamily[110X[133X
  
  
  [1X54.2 [33X[0;0YCreating partial permutations[133X[101X
  
  [33X[0;0YThere  are  several  ways of creating partial permutations in [5XGAP[105X, which are
  described in this section.[133X
  
  [1X54.2-1 PartialPerm[101X
  
  [29X[2XPartialPerm[102X( [3Xdom[103X, [3Ximg[103X ) [32X function
  [29X[2XPartialPerm[102X( [3Xlist[103X ) [32X function
  [6XReturns:[106X  [33X[0;10YA partial permutation.[133X
  
  [33X[0;0YPartial  permutations  can  be created in two ways: by giving the domain and
  the image, or the dense image list.[133X
  
  [8XDomain and image[108X
        [33X[0;6YThe  partial  permutation defined by a domain [3Xdom[103X and image [3Ximg[103X, where
        [3Xdom[103X  is a set of positive integers and [3Ximg[103X is a duplicate free list of
        positive  integers,  maps  [3Xdom[103X[10X[i][110X  to [3Ximg[103X[10X[i][110X. For example, the partial
        permutation mapping [10X1[110X and [10X5[110X to [10X20[110X and [10X2[110X can be created using:[133X
  
  [4X      [32X  Example  [32X[104X
          [4X[28XPartialPerm([1,5],[20,2]); [128X[104X
        [4X[32X[104X
  
        [33X[0;6YIn this setting, [10XPartialPerm[110X is the analogue in the context of partial
        permutations of [2XMappingPermListList[102X ([14X42.5-3[114X).[133X
  
  [8XDense image list[108X
        [33X[0;6YThe  partial  permutation defined by a dense image list [3Xlist[103X, maps the
        positive  integer  [10Xi[110X to [3Xlist[103X[10X[i][110X if [3Xlist[103X[10X[i]<>0[110X and is undefined at [10Xi[110X if
        [3Xlist[103X[10X[i]=0[110X.  For example, the partial permutation mapping [10X1[110X and [10X5[110X to [10X20[110X
        and [10X2[110X can be created using:[133X
  
  [4X      [32X  Example  [32X[104X
          [4X[28XPartialPerm([20,0,0,0,2]);[128X[104X
        [4X[32X[104X
  
        [33X[0;6YIn this setting, [10XPartialPerm[110X is the analogue in the context of partial
        permutations of [2XPermList[102X ([14X42.5-2[114X).[133X
  
  [33X[0;0YRegardless  of  which  of  these  two  methods  are used to create a partial
  permutation in [5XGAP[105X the internal representation is the same.[133X
  
  [33X[0;0YIf  the  largest  point in the domain is larger than the rank of the partial
  permutation,  then  using  the  dense  image  list  to  define  the  partial
  permutation  will  require  less  typing; otherwise using the domain and the
  image will require less typing. For example, the partial permutation mapping
  [10X10000[110X to [10X1[110X can be defined using:[133X
  
  [4X[32X  Example  [32X[104X
    [4X[28XPartialPerm([10000], [1]);[128X[104X
  [4X[32X[104X
  
  [33X[0;0Ybut  using the dense image list would require a list with [10X9999[110X entries equal
  to  [10X0[110X  and  the  final  entry equal to [10X1[110X. On the other hand, the identity on
  [10X[1,2,3,4,6][110X can be defined using:[133X
  
  [4X[32X  Example  [32X[104X
    [4X[28XPartialPerm([1,2,3,4,0,6]);[128X[104X
  [4X[32X[104X
  
  [33X[0;0YPlease  note that a partial permutation in [5XGAP[105X is never a permutation nor is
  a  permutation  ever  a  partial  permutation.  For example, the permutation
  [10X(1,4,2)[110X  fixes  [10X3[110X but the partial permutation [10XPartialPerm([4,1,0,2]);[110X is not
  defined on [10X3[110X.[133X
  
  [1X54.2-2 PartialPermOp[101X
  
  [29X[2XPartialPermOp[102X( [3Xobj[103X, [3Xlist[103X[, [3Xfunc[103X] ) [32X function
  [29X[2XPartialPermOpNC[102X( [3Xobj[103X, [3Xlist[103X[, [3Xfunc[103X] ) [32X function
  [6XReturns:[106X  [33X[0;10YA partial permutation or [9Xfail[109X.[133X
  
  [33X[0;0Y[10XPartialPermOp[110X returns the partial permutation that corresponds to the action
  of  the  object [3Xobj[103X on the domain or list [3Xlist[103X via the function [3Xfunc[103X. If the
  optional  third  argument  [3Xfunc[103X  is  not specified, then the action [2XOnPoints[102X
  ([14X41.2-1[114X)  is  used  by  default.  Note that the returned partial permutation
  refers to the positions in [3Xlist[103X even if [3Xlist[103X itself consists of integers.[133X
  
  [33X[0;0YThis  function  is  the  analogue  in the context of partial permutations of
  [2XPermutation[102X ([14XReference: Permutation[114X) or [2XTransformationOp[102X ([14X53.2-5[114X).[133X
  
  [33X[0;0YIf [3Xobj[103X does not map the elements of [3Xlist[103X injectively, then [9Xfail[109X is returned.[133X
  
  [33X[0;0Y[10XPartialPermOpNC[110X does not check that [3Xobj[103X maps elements of [3Xlist[103X injectively or
  that a partial permutation is defined by the action of [3Xobj[103X on [3Xlist[103X via [3Xfunc[103X.
  This  function  should  be used only with caution, in situations where it is
  guaranteed that the arguments have the required properties.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=Transformation( [ 9, 10, 4, 2, 10, 5, 9, 10, 9, 6 ] );;[127X[104X
    [4X[25Xgap>[125X [27XPartialPermOp(f, [ 6 .. 8 ], OnPoints);[127X[104X
    [4X[28X[1,4][2,5][3,6][128X[104X
  [4X[32X[104X
  
  [1X54.2-3 RestrictedPartialPerm[101X
  
  [29X[2XRestrictedPartialPerm[102X( [3Xf[103X, [3Xset[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA partial permutation.[133X
  
  [33X[0;0Y[10XRestrictedPartialPerm[110X  returns  a  new  partial permutation that acts on the
  points  in  the  set of positive integers [3Xset[103X in the same way as the partial
  permutation [3Xf[103X, and that is undefined on those points that are not in [3Xset[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 3, 4, 7, 8, 9 ], [ 9, 4, 1, 6, 2, 8 ] );;[127X[104X
    [4X[25Xgap>[125X [27XRestrictedPartialPerm(f, [ 2, 3, 6, 10 ] );[127X[104X
    [4X[28X[3,4][128X[104X
  [4X[32X[104X
  
  [1X54.2-4 JoinOfPartialPerms[101X
  
  [29X[2XJoinOfPartialPerms[102X( [3Xarg[103X ) [32X function
  [29X[2XJoinOfIdempotentPartialPermsNC[102X( [3Xarg[103X ) [32X function
  [6XReturns:[106X  [33X[0;10YA partial permutation or [9Xfail[109X.[133X
  
  [33X[0;0YThe join of partial permutations [3Xf[103X and [3Xg[103X is just the join, or supremum, of [3Xf[103X
  and [3Xg[103X under the natural partial ordering of partial permutations.[133X
  
  [33X[0;0Y[10XJoinOfPartialPerms[110X  returns  the  union  of  the partial permutations in its
  argument  if  this defines a partial permutation, and [9Xfail[109X if it is not. The
  argument  [3Xarg[103X can be a partial permutation collection or a number of partial
  permutations.[133X
  
  [33X[0;0YThe function [10XJoinOfIdempotentPartialPermsNC[110X returns the join of its argument
  which  is assumed to be a collection of idempotent partial permutations or a
  number  of  idempotent  partial  permutations.  It  is  not checked that the
  arguments  are  idempotents. The performance of this function is higher than
  [10XJoinOfPartialPerms[110X  when  it is known [13Xa priori[113X that the argument consists of
  idempotents.[133X
  
  [33X[0;0YThe  union  of [3Xf[103X and [3Xg[103X is a partial permutation if and only if [3Xf[103X and [3Xg[103X agree
  on  the  intersection  dom([3Xf[103X)[22X∩[122X  dom([3Xg[103X)  of  their  domains and the images of
  dom([3Xf[103X)[22X∖[122X dom([3Xg[103X) and dom([3Xg[103X)[22X∖[122X dom([3Xf[103X) under [3Xf[103X and [3Xg[103X, respectively, are disjoint.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6, 8, 10 ], [ 2, 6, 7, 9, 1, 5 ] );[127X[104X
    [4X[28X[3,7][8,1,2,6,9][10,5][128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 11, 12, 14, 16, 18, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 17, 20, 11, 19, 14, 12 ] );[127X[104X
    [4X[28X[16,19,12,20][18,14,11,17][128X[104X
    [4X[25Xgap>[125X [27XJoinOfPartialPerms(f, g);[127X[104X
    [4X[28X[3,7][8,1,2,6,9][10,5][16,19,12,20][18,14,11,17][128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 4, 5, 6, 7 ], [ 5, 7, 3, 1, 4 ] );[127X[104X
    [4X[28X[6,1,5,3](4,7)[128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 100 ], [ 1 ] );[127X[104X
    [4X[28X[100,1][128X[104X
    [4X[25Xgap>[125X [27XJoinOfPartialPerms(f, g);[127X[104X
    [4X[28Xfail[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 3, 4 ], [ 3, 2, 4 ] );[127X[104X
    [4X[28X[1,3,2](4)[128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 1, 2, 4 ], [ 2, 3, 4 ] );[127X[104X
    [4X[28X[1,2,3](4)[128X[104X
    [4X[25Xgap>[125X [27XJoinOfPartialPerms(f, g);[127X[104X
    [4X[28Xfail[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1 ], [ 2 ] ); [127X[104X
    [4X[28X[1,2][128X[104X
    [4X[25Xgap>[125X [27XJoinOfPartialPerms(f, f^-1);[127X[104X
    [4X[28X(1,2)[128X[104X
  [4X[32X[104X
  
  [1X54.2-5 MeetOfPartialPerms[101X
  
  [29X[2XMeetOfPartialPerms[102X( [3Xarg[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA partial permutation.[133X
  
  [33X[0;0YThe  meet of partial permutations [3Xf[103X and [3Xg[103X is just the meet, or infimum, of [3Xf[103X
  and  [3Xg[103X  under the natural partial ordering of partial permutations. In other
  words, the meet is the greatest partial permuation which is a restriction of
  both [3Xf[103X and [3Xg[103X.[133X
  
  [33X[0;0YNote that unlike the join of partial permutations, the meet always exists.[133X
  
  [33X[0;0Y[10XMeetOfPartialPerms[110X  returns  the  meet  of  the  partial permutations in its
  argument.  The  argument  [3Xarg[103X  can  be a partial permutation collection or a
  number of partial permutations.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6, 100000 ], [ 2, 6, 7, 1, 5 ] );[127X[104X
    [4X[28X[3,7][100000,5](1,2,6)[128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 1, 2, 3, 4, 6 ], [ 2, 4, 6, 1, 5 ] );[127X[104X
    [4X[28X[3,6,5](1,2,4)[128X[104X
    [4X[25Xgap>[125X [27XMeetOfPartialPerms(f, g);[127X[104X
    [4X[28X[1,2][128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 1, 2, 3, 5, 6, 7, 9, 10 ], [127X[104X
    [4X[25X>[125X [27X[ 4, 10, 5, 6, 7, 1, 3, 2 ] );[127X[104X
    [4X[28X[9,3,5,6,7,1,4](2,10)[128X[104X
    [4X[25Xgap>[125X [27XMeetOfPartialPerms(f, g);[127X[104X
    [4X[28X<empty partial perm>[128X[104X
  [4X[32X[104X
  
  [1X54.2-6 EmptyPartialPerm[101X
  
  [29X[2XEmptyPartialPerm[102X(  ) [32X function
  [6XReturns:[106X  [33X[0;10YThe empty partial permutation.[133X
  
  [33X[0;0YThe empty partial permutation is returned by this function when it is called
  with no arguments. This is just short hand for [10XPartialPerm([]);[110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XEmptyPartialPerm();[127X[104X
    [4X[28X<empty partial perm>[128X[104X
  [4X[32X[104X
  
  
  [1X54.2-7 [33X[0;0YRandomPartialPerm[133X[101X
  
  [29X[2XRandomPartialPerm[102X( [3Xn[103X ) [32X operation
  [29X[2XRandomPartialPerm[102X( [3Xset[103X ) [32X operation
  [29X[2XRandomPartialPerm[102X( [3Xdom[103X, [3Ximg[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA random partial permutation.[133X
  
  [33X[0;0YIn  its  first  form,  [10XRandomPartialPerm[110X  returns  a randomly chosen partial
  permutation  where  points  in the domain and image are bounded above by the
  positive integer [3Xn[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XRandomPartialPerm(10);  [127X[104X
    [4X[28X[2,9][4,1,6,5][7,3](8)[128X[104X
  [4X[32X[104X
  
  [33X[0;0YIn  its  second  form,  [10XRandomPartialPerm[110X  returns a randomly chosen partial
  permutation  with  points  in  the  domain and image contained in the set of
  positive integers [3Xset[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XRandomPartialPerm([1,2,3,1000]);[127X[104X
    [4X[28X[2,3,1000](1)[128X[104X
  [4X[32X[104X
  
  [33X[0;0YIn  its  third  form,  [10XRandomPartialPerm[110X  creates  a randomly chosen partial
  permutation  with  domain  contained in the set of positive integers [3Xdom[103X and
  image  contained  in the set of positive integers [3Ximg[103X. The arguments [3Xdom[103X and
  [3Ximg[103X do not have to have equal length.[133X
  
  [33X[0;0YNote  that  it  is  not  guarenteed  in  either  of these cases that partial
  permutations are chosen with a uniform distribution.[133X
  
  
  [1X54.3 [33X[0;0YAttributes for partial permutations[133X[101X
  
  [33X[0;0YIn  this  section  we  describe  the  functions available in [5XGAP[105X for finding
  various attributes of partial permutations.[133X
  
  [1X54.3-1 DegreeOfPartialPerm[101X
  
  [29X[2XDegreeOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [29X[2XDegreeOfPartialPermCollection[102X( [3Xcoll[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA non-negative integer.[133X
  
  [33X[0;0YThe  [13Xdegree[113X of a partial permutation [3Xf[103X is the largest positive integer where
  it is defined, i.e. the maximum element in the domain of [3Xf[103X.[133X
  
  [33X[0;0YThe  degree  a collection of partial permutations [3Xcoll[103X is the largest degree
  of any partial permutation in [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6, 8, 10 ], [ 2, 6, 7, 9, 1, 5 ] );[127X[104X
    [4X[28X[3,7][8,1,2,6,9][10,5][128X[104X
    [4X[25Xgap>[125X [27XDegreeOfPartialPerm(f);[127X[104X
    [4X[28X10[128X[104X
  [4X[32X[104X
  
  [1X54.3-2 CodegreeOfPartialPerm[101X
  
  [29X[2XCodegreeOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [29X[2XCodegreeOfPartialPermCollection[102X( [3Xcoll[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA non-negative integer.[133X
  
  [33X[0;0YThe  [13Xcodegree[113X  of a partial permutation [3Xf[103X is the largest positive integer in
  its image.[133X
  
  [33X[0;0YThe  codegree  a  collection  of  partial  permutations  [3Xcoll[103X is the largest
  codegree of any partial permutation in [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 8, 10 ], [ 7, 1, 4, 3, 2, 6, 5 ] );[127X[104X
    [4X[28X[8,6][10,5,2,1,7](3,4)[128X[104X
    [4X[25Xgap>[125X [27XCodegreeOfPartialPerm(f);[127X[104X
    [4X[28X7[128X[104X
  [4X[32X[104X
  
  [1X54.3-3 RankOfPartialPerm[101X
  
  [29X[2XRankOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [29X[2XRankOfPartialPermCollection[102X( [3Xcoll[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA non-negative integer.[133X
  
  [33X[0;0YThe  [13Xrank[113X  of  a  partial  permutation  [3Xf[103X  is  the  size  of  its domain, or
  equivalently the size of its image set or image list.[133X
  
  [33X[0;0YThe  rank  of a partial permutation collection [3Xcoll[103X is the size of the union
  of the domains of the elements of [3Xcoll[103X, or equivalently, the total number of
  points  on  which  the elements of [3Xcoll[103X act. Note that this is value may not
  the same as the size of the union of the images of the elements in [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 4, 6, 8, 9 ], [ 7, 10, 1, 9, 4, 2 ] );[127X[104X
    [4X[28X[6,9,2,10][8,4,1,7][128X[104X
    [4X[25Xgap>[125X [27XRankOfPartialPerm(f);[127X[104X
    [4X[28X6[128X[104X
  [4X[32X[104X
  
  [1X54.3-4 DomainOfPartialPerm[101X
  
  [29X[2XDomainOfPartialPerm[102X( [3Xf[103X ) [32X operation
  [29X[2XDomainOfPartialPermCollection[102X( [3Xf[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA set of positive integers (maybe empty).[133X
  
  [33X[0;0YThe  [13Xdomain[113X of a partial permutation [3Xf[103X is the set of positive integers where
  [3Xf[103X is defined.[133X
  
  [33X[0;0YThe  domain  of  a  partial  permutation collection [3Xcoll[103X is the union of the
  domains of its elements.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6, 8, 10 ], [ 2, 6, 7, 9, 1, 5 ] );[127X[104X
    [4X[28X[3,7][8,1,2,6,9][10,5][128X[104X
    [4X[25Xgap>[125X [27XDomainOfPartialPerm(f);[127X[104X
    [4X[28X[ 1, 2, 3, 6, 8, 10 ][128X[104X
  [4X[32X[104X
  
  [1X54.3-5 ImageOfPartialPermCollection[101X
  
  [29X[2XImageOfPartialPermCollection[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA set of positive integers (maybe empty).[133X
  
  [33X[0;0YThe  [13Ximage[113X  of  a  partial  permutation  collection [3Xcoll[103X is the union of the
  images of its elements.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=SymmetricInverseSemigroup(5);                                [127X[104X
    [4X[28X<symmetric inverse semigroup on 5 pts>[128X[104X
    [4X[25Xgap>[125X [27XImageOfPartialPermCollection(GeneratorsOfInverseSemigroup(S));[127X[104X
    [4X[28X[ 1, 2, 3, 4, 5 ][128X[104X
  [4X[32X[104X
  
  [1X54.3-6 ImageListOfPartialPerm[101X
  
  [29X[2XImageListOfPartialPerm[102X( [3Xf[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YThe list of images of a partial permutation.[133X
  
  [33X[0;0YThe  [13Ximage  list[113X  of  a  partial  permutation [3Xf[103X is the list of images of the
  elements           of          the          domain          [3Xf[103X          where
  [10XImageListOfPartialPerm([3Xf[103X[10X)[i]=DomainOfPartialPerm([3Xf[103X[10X)[i]^[3Xf[103X[10X[110X  for  any  [10Xi[110X in the
  range from [10X1[110X to the rank of [3Xf[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 8, 10 ], [ 7, 1, 4, 3, 2, 6, 5 ] );[127X[104X
    [4X[28X[8,6][10,5,2,1,7](3,4)[128X[104X
    [4X[25Xgap>[125X [27XImageListOfPartialPerm(f);[127X[104X
    [4X[28X[ 7, 1, 4, 3, 2, 6, 5 ][128X[104X
  [4X[32X[104X
  
  [1X54.3-7 ImageSetOfPartialPerm[101X
  
  [29X[2XImageSetOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YThe image set of a partial permutation.[133X
  
  [33X[0;0YThe  [13Ximage  set[113X  of a partial permutation [10Xf[110X is just the set of points in the
  image  list  (i.e.  the  image list after it has been sorted into increasing
  order).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 5, 7, 10 ], [ 10, 2, 3, 5, 7, 6 ] );[127X[104X
    [4X[28X[1,10,6](2)(3)(5)(7)[128X[104X
    [4X[25Xgap>[125X [27XImageSetOfPartialPerm(f);[127X[104X
    [4X[28X[ 2, 3, 5, 6, 7, 10 ][128X[104X
  [4X[32X[104X
  
  [1X54.3-8 FixedPointsOfPartialPerm[101X
  
  [29X[2XFixedPointsOfPartialPerm[102X( [3Xf[103X ) [32X operation
  [29X[2XFixedPointsOfPartialPerm[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA set of positive integers.[133X
  
  [33X[0;0Y[10XFixedPointsOfPartialPerm[110X  returns  the  set of points [10Xi[110X in the domain of the
  partial permutation [3Xf[103X such that [10Xi^[3Xf[103X[10X=i[110X.[133X
  
  [33X[0;0YWhen   the   argument   is   a  collection  of  partial  permutations  [3Xcoll[103X,
  [10XFixedPointsOfPartialPerm[110X returns the set of points fixed by every element of
  the collection of partial permutations [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ], [127X[104X
    [4X[25X>[125X [27X[ 30, 20, 29, 24, 9, 14, 26, 5, 25, 15, 11, 6, 35, 2, 10, 19, 23 ] );;[127X[104X
    [4X[25Xgap>[125X [27XFixedPointsOfPartialPerm(f);[127X[104X
    [4X[28X[  ][128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1..10]);;[127X[104X
    [4X[25Xgap>[125X [27XFixedPointsOfPartialPerm(f);[127X[104X
    [4X[28X[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ][128X[104X
  [4X[32X[104X
  
  [1X54.3-9 MovedPoints[101X
  
  [29X[2XMovedPoints[102X( [3Xf[103X ) [32X operation
  [29X[2XMovedPoints[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA set of positive integers.[133X
  
  [33X[0;0Y[10XMovedPoints[110X  returns  the  set  of  points  [10Xi[110X  in  the domain of the partial
  permutation [3Xf[103X such that [10Xi^[3Xf[103X[10X<>i[110X.[133X
  
  [33X[0;0YWhen  the argument is a collection of partial permutations [3Xcoll[103X, [10XMovedPoints[110X
  returns the set of points moved by some element of the collection of partial
  permutations [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ], [127X[104X
    [4X[25X>[125X [27X[ 30, 20, 29, 24, 9, 14, 26, 5, 25, 15, 11, 6, 35, 2, 10, 19, 23 ] );;[127X[104X
    [4X[25Xgap>[125X [27XFixedPointsOfPartialPerm(f);[127X[104X
    [4X[28X[  ][128X[104X
    [4X[25Xgap>[125X [27XMovedPoints(f);[127X[104X
    [4X[28X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ][128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1..10]);;[127X[104X
    [4X[25Xgap>[125X [27XFixedPointsOfPartialPerm(f);[127X[104X
    [4X[28X[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ][128X[104X
    [4X[25Xgap>[125X [27XMovedPoints(f);[127X[104X
    [4X[28X[  ][128X[104X
  [4X[32X[104X
  
  [1X54.3-10 NrFixedPoints[101X
  
  [29X[2XNrFixedPoints[102X( [3Xf[103X ) [32X operation
  [29X[2XNrFixedPoints[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer.[133X
  
  [33X[0;0Y[10XNrFixedPoints[110X  returns  the  number of points [10Xi[110X in the domain of the partial
  permutation [3Xf[103X such that [10Xi^[3Xf[103X[10X=i[110X.[133X
  
  [33X[0;0YWhen   the   argument   is   a  collection  of  partial  permutations  [3Xcoll[103X,
  [10XNrFixedPoints[110X  returns  the  number  of points fixed by every element of the
  collection of partial permutations [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ], [127X[104X
    [4X[25X>[125X [27X[ 30, 20, 29, 24, 9, 14, 26, 5, 25, 15, 11, 6, 35, 2, 10, 19, 23 ] );;[127X[104X
    [4X[25Xgap>[125X [27XNrFixedPoints(f);[127X[104X
    [4X[28X0[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1..10]);;[127X[104X
    [4X[25Xgap>[125X [27XNrFixedPoints(f);[127X[104X
    [4X[28X10[128X[104X
  [4X[32X[104X
  
  [1X54.3-11 NrMovedPoints[101X
  
  [29X[2XNrMovedPoints[102X( [3Xf[103X ) [32X operation
  [29X[2XNrMovedPoints[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer.[133X
  
  [33X[0;0Y[10XNrMovedPoints[110X  returns  the  number of points [10Xi[110X in the domain of the partial
  permutation [3Xf[103X such that [10Xi^[3Xf[103X[10X<>i[110X.[133X
  
  [33X[0;0YWhen   the   argument   is   a  collection  of  partial  permutations  [3Xcoll[103X,
  [10XNrMovedPoints[110X  returns  the  number  of  points moved by some element of the
  collection of partial permutations [3Xcoll[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ], [127X[104X
    [4X[25X>[125X [27X[ 30, 20, 29, 24, 9, 14, 26, 5, 25, 15, 11, 6, 35, 2, 10, 19, 23 ] );;[127X[104X
    [4X[25Xgap>[125X [27XNrMovedPoints(f);[127X[104X
    [4X[28X17[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1..10]);;[127X[104X
    [4X[25Xgap>[125X [27XNrMovedPoints(f);[127X[104X
    [4X[28X0[128X[104X
  [4X[32X[104X
  
  [1X54.3-12 SmallestMovedPoint[101X
  
  [29X[2XSmallestMovedPoint[102X( [3Xf[103X ) [32X operation
  [29X[2XSmallestMovedPoint[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer or [9Xinfinity[109X.[133X
  
  [33X[0;0Y[10XSmallestMovedPoint[110X  returns the smallest positive integer [10Xi[110X such that [10Xi^[3Xf[103X[10X<>i[110X
  if  such an [10Xi[110X exists. If [3Xf[103X is an identity partial permutation, then [9Xinfinity[109X
  is returned.[133X
  
  [33X[0;0YIf  the  argument  is  a  collection  of partial permutations [3Xcoll[103X, then the
  smallest  point  which is moved by at least one element of [3Xcoll[103X is returned,
  if such a point exists. If [3Xcoll[103X only contains identity partial permutations,
  then [10XSmallestMovedPoint[110X returns [9Xinfinity[109X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ], [127X[104X
    [4X[25X>[125X [27X[ 30, 20, 29, 24, 9, 14, 26, 5, 25, 15, 11, 6, 35, 2, 10, 19, 23 ] );[127X[104X
    [4X[28X[1,30][3,29][8,14,25,10,26,19][17,15][21,6,9][22,35][32,23][128X[104X
    [4X[28X(2,20,11,5,24)[128X[104X
    [4X[25Xgap>[125X [27XSmallestMovedPoint(f);[127X[104X
    [4X[28X1[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1..10]);;[127X[104X
    [4X[25Xgap>[125X [27XSmallestMovedPoint(f);[127X[104X
    [4X[28Xinfinity[128X[104X
  [4X[32X[104X
  
  [1X54.3-13 LargestMovedPoint[101X
  
  [29X[2XLargestMovedPoint[102X( [3Xf[103X ) [32X operation
  [29X[2XLargestMovedPoint[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer or [9Xinfinity[109X.[133X
  
  [33X[0;0Y[10XLargestMovedPoint[110X  returns  the largest positive integers [10Xi[110X such that [10Xi^[3Xf[103X[10X<>i[110X
  if  such  an  [10Xi[110X  exists. If [3Xf[103X is the identity partial permutation, then [10X0[110X is
  returned.[133X
  
  [33X[0;0YIf  the  argument  is  a  collection  of partial permutations [3Xcoll[103X, then the
  largest point which is moved by at least one element of [3Xcoll[103X is returned, if
  such  a  point  exists. If [3Xcoll[103X only contains identity partial permutations,
  then [10XLargestMovedPoint[110X returns [10X0[110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 5, 6, 8, 10, 11, 14, 17, 20, 21, 22, 24, 25, 26, 32 ], [127X[104X
    [4X[25X>[125X [27X[ 30, 20, 29, 24, 9, 14, 26, 5, 25, 15, 11, 6, 35, 2, 10, 19, 23 ] );[127X[104X
    [4X[28X[1,30][3,29][8,14,25,10,26,19][17,15][21,6,9][22,35][32,23][128X[104X
    [4X[28X(2,20,11,5,24)[128X[104X
    [4X[25Xgap>[125X [27XLargestMovedPoint(f);[127X[104X
    [4X[28X32[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1..10]);;[127X[104X
    [4X[25Xgap>[125X [27XLargestMovedPoint(f);[127X[104X
    [4X[28X0[128X[104X
  [4X[32X[104X
  
  [1X54.3-14 SmallestImageOfMovedPoint[101X
  
  [29X[2XSmallestImageOfMovedPoint[102X( [3Xf[103X ) [32X operation
  [29X[2XSmallestImageOfMovedPoint[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer or [9Xinfinity[109X.[133X
  
  [33X[0;0Y[10XSmallestImageOfMovedPoint[110X  returns  the  smallest  positive integer [10Xi^[3Xf[103X[10X[110X such
  that  [10Xi^[3Xf[103X[10X<>i[110X  if such an [10Xi[110X exists. If [3Xf[103X is the identity partial permutation,
  then [9Xinfinity[109X is returned.[133X
  
  [33X[0;0YIf  the  argument  is  a  collection  of partial permutations [3Xcoll[103X, then the
  smallest integer which is the image a point moved by at least one element of
  [3Xcoll[103X  is  returned,  if  such a point exists. If [3Xcoll[103X only contains identity
  partial permutations, then [10XSmallestImageOfMovedPoint[110X returns [9Xinfinity[109X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=SymmetricInverseSemigroup(5);[127X[104X
    [4X[28X<symmetric inverse semigroup on 5 pts>[128X[104X
    [4X[25Xgap>[125X [27XSmallestImageOfMovedPoint(S);[127X[104X
    [4X[28X1[128X[104X
    [4X[25Xgap>[125X [27XS:=Semigroup(PartialPerm([10..100], [10..100]));;[127X[104X
    [4X[25Xgap>[125X [27XSmallestImageOfMovedPoint(S);[127X[104X
    [4X[28Xinfinity[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6 ] );;[127X[104X
    [4X[25Xgap>[125X [27XSmallestImageOfMovedPoint(f);[127X[104X
    [4X[28X6[128X[104X
  [4X[32X[104X
  
  [1X54.3-15 LargestImageOfMovedPoint[101X
  
  [29X[2XLargestImageOfMovedPoint[102X( [3Xf[103X ) [32X operation
  [29X[2XLargestImageOfMovedPoint[102X( [3Xcoll[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer.[133X
  
  [33X[0;0Y[10XLargestImageOfMovedPoint[110X  returns the largest positive integer [10Xi^[3Xf[103X[10X[110X such that
  [10Xi^[3Xf[103X[10X<>i[110X  if such an [10Xi[110X exists. If [3Xf[103X is an identity partial permutation, then [10X0[110X
  is returned.[133X
  
  [33X[0;0YIf  the  argument  is  a  collection  of partial permutations [3Xcoll[103X, then the
  largest  integer which is the image of a point moved by at least one element
  of  [3Xcoll[103X is returned, if such a point exists. If [3Xcoll[103X only contains identity
  partial permutations, then [10XLargestImageOfMovedPoint[110X returns [10X0[110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=SymmetricInverseSemigroup(5);[127X[104X
    [4X[28X<symmetric inverse semigroup on 5 pts>[128X[104X
    [4X[25Xgap>[125X [27XLargestImageOfMovedPoint(S);[127X[104X
    [4X[28X5[128X[104X
    [4X[25Xgap>[125X [27XS:=Semigroup(PartialPerm([10..100], [10..100]));;[127X[104X
    [4X[25Xgap>[125X [27XLargestImageOfMovedPoint(S);[127X[104X
    [4X[28X0[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6 ] );;[127X[104X
    [4X[25Xgap>[125X [27XLargestImageOfMovedPoint(f);[127X[104X
    [4X[28X6[128X[104X
  [4X[32X[104X
  
  [1X54.3-16 IndexPeriodOfPartialPerm[101X
  
  [29X[2XIndexPeriodOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA pair of positive integers.[133X
  
  [33X[0;0YReturns  the  least  positive integers [10Xm, r[110X such that [10X[3Xf[103X[10X^(m+r)=[3Xf[103X[10X^m[110X, which are
  known as the [13Xindex[113X and [13Xperiod[113X of the partial permutation [3Xf[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 5, 6, 7, 8, 11, 12, 16, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 9, 18, 20, 11, 5, 16, 8, 19, 14, 13, 1 ] );[127X[104X
    [4X[28X[2,18][3,20][6,5,11,19,1,9][7,16,13][12,14](8)[128X[104X
    [4X[25Xgap>[125X [27XIndexPeriodOfPartialPerm(f);[127X[104X
    [4X[28X[ 6, 1 ][128X[104X
    [4X[25Xgap>[125X [27Xf^6=f^7;[127X[104X
    [4X[28Xtrue[128X[104X
  [4X[32X[104X
  
  [1X54.3-17 SmallestIdempotentPower[101X
  
  [29X[2XSmallestIdempotentPower[102X( [3Xf[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA positive integer.[133X
  
  [33X[0;0YThis  function  returns  the  least positive integer [10Xn[110X such that the partial
  permutation  [10X[3Xf[103X[10X^n[110X is an idempotent. The smallest idempotent power of [3Xf[103X is the
  least multiple of the period of [3Xf[103X that is greater than or equal to the index
  of [3Xf[103X; see [2XIndexPeriodOfPartialPerm[102X ([14X54.3-16[114X).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 7, 8, 10, 11, 13, 18, 19, 20 ], [127X[104X
    [4X[25X>[125X [27X[ 5, 1, 7, 3, 10, 2, 12, 14, 11, 16, 6, 9, 15 ] );[127X[104X
    [4X[28X[4,3,7,2,1,5,10,14][8,12][13,16][18,6][19,9][20,15](11)[128X[104X
    [4X[25Xgap>[125X [27XSmallestIdempotentPower(f);[127X[104X
    [4X[28X8[128X[104X
    [4X[25Xgap>[125X [27Xf^8;[127X[104X
    [4X[28X<identity partial perm on [ 11 ]>[128X[104X
  [4X[32X[104X
  
  [1X54.3-18 ComponentsOfPartialPerm[101X
  
  [29X[2XComponentsOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA list of lists of positive integer.[133X
  
  [33X[0;0Y[10XComponentsOfPartialPerm[110X  returns  a  list  of  the components of the partial
  permutation  [3Xf[103X. Each component is a subset of the domain of [3Xf[103X, and the union
  of the components equals the domain.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 13, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 20, 4, 6, 19, 9, 14, 3, 12, 17, 5, 15, 13 ] );[127X[104X
    [4X[28X[1,20][2,4,19,13,15][7,14][8,3,6][10,12,5,9][11,17][128X[104X
    [4X[25Xgap>[125X [27XComponentsOfPartialPerm(f);[127X[104X
    [4X[28X[ [ 1, 20 ], [ 2, 4, 19, 13, 15 ], [ 7, 14 ], [ 8, 3, 6 ], [128X[104X
    [4X[28X  [ 10, 12, 5, 9 ], [ 11, 17 ] ][128X[104X
  [4X[32X[104X
  
  [1X54.3-19 NrComponentsOfPartialPerm[101X
  
  [29X[2XNrComponentsOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA positive integer.[133X
  
  [33X[0;0Y[10XNrComponentsOfPartialPerm[110X  returns  the  number of components of the partial
  permutation [3Xf[103X on its domain.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 13, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 20, 4, 6, 19, 9, 14, 3, 12, 17, 5, 15, 13 ] );[127X[104X
    [4X[28X[1,20][2,4,19,13,15][7,14][8,3,6][10,12,5,9][11,17][128X[104X
    [4X[25Xgap>[125X [27XNrComponentsOfPartialPerm(f);[127X[104X
    [4X[28X6[128X[104X
  [4X[32X[104X
  
  [1X54.3-20 ComponentRepsOfPartialPerm[101X
  
  [29X[2XComponentRepsOfPartialPerm[102X( [3Xf[103X ) [32X attribute
  
  [33X[0;0Y[10XComponentRepsOfPartialPerm[110X  returns  the  representatives,  in the following
  sense,  of  the  components of the partial permutation [3Xf[103X. For every [10Xi[110X in the
  domain  of  [3Xf[103X  there exists a representative [10Xj[110X and a positive integer [10Xk[110X such
  that  [10Xi^([3Xf[103X[10X^k)=j[110X. Unlike transformations, there is exactly one representative
  for  every  component  of  [3Xf[103X.  [10XComponentRepsOfPartialPerm[110X  returns the least
  number of representatives.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 13, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 20, 4, 6, 19, 9, 14, 3, 12, 17, 5, 15, 13 ] );[127X[104X
    [4X[28X[1,20][2,4,19,13,15][7,14][8,3,6][10,12,5,9][11,17][128X[104X
    [4X[25Xgap>[125X [27XComponentRepsOfPartialPerm(f);[127X[104X
    [4X[28X[ 1, 2, 7, 8, 10, 11 ][128X[104X
  [4X[32X[104X
  
  [1X54.3-21 LeftOne[101X
  
  [29X[2XLeftOne[102X( [3Xf[103X ) [32X attribute
  [29X[2XRightOne[102X( [3Xf[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA partial permutation.[133X
  
  [33X[0;0Y[10XLeftOne[110X  returns the identity partial permutation [10Xe[110X such that the domain and
  image  of  [10Xe[110X  equal  the  domain  of the partial permutation [3Xf[103X and such that
  [10Xe*[3Xf[103X[10X=f[110X.[133X
  
  [33X[0;0Y[10XRightOne[110X returns the identity partial permutation [10Xe[110X such that the domain and
  image of [10Xe[110X equal the image of [3Xf[103X and such that [10X[3Xf[103X[10X*e=f[110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 4, 5, 6, 7 ], [ 10, 1, 6, 5, 8, 7 ] ); [127X[104X
    [4X[28X[2,1,10][4,6,8](5)(7)[128X[104X
    [4X[25Xgap>[125X [27XRightOne(f);[127X[104X
    [4X[28X<identity partial perm on [ 1, 5, 6, 7, 8, 10 ]>[128X[104X
    [4X[25Xgap>[125X [27XLeftOne(f);[127X[104X
    [4X[28X<identity partial perm on [ 1, 2, 4, 5, 6, 7 ]>[128X[104X
  [4X[32X[104X
  
  [1X54.3-22 One[101X
  
  [29X[2XOne[102X( [3Xf[103X ) [32X method
  [6XReturns:[106X  [33X[0;10YA partial permutation.[133X
  
  [33X[0;0YAs  described  in  [2XOneImmutable[102X  ([14XReference:  OneImmutable[114X), [10XOne[110X returns the
  multiplicative  neutral  element  of the partial permutation [3Xf[103X, which is the
  identity  partial  permutation  on  the  union of the domain and image of [3Xf[103X.
  Equivalently, the one of [3Xf[103X is the join of the right one and left one of [3Xf[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([ 1, 2, 3, 4, 5, 7, 10 ], [ 3, 7, 9, 6, 1, 10, 2 ]);;[127X[104X
    [4X[25Xgap>[125X [27XOne(f);[127X[104X
    [4X[28X<identity partial perm on [ 1, 2, 3, 4, 5, 6, 7, 9, 10 ]>[128X[104X
  [4X[32X[104X
  
  [1X54.3-23 Zero[101X
  
  [29X[2XZero[102X( [3Xf[103X ) [32X method
  [6XReturns:[106X  [33X[0;10YThe empty partial permutation.[133X
  
  [33X[0;0YAs  described  in [2XZeroImmutable[102X ([14XReference: ZeroImmutable[114X), [10XZero[110X returns the
  multiplicative zero element of the partial permutation [3Xf[103X, which is the empty
  partial permutation.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([ 1, 2, 3, 4, 5, 7, 10 ], [ 3, 7, 9, 6, 1, 10, 2 ]);;[127X[104X
    [4X[25Xgap>[125X [27XZero(f);[127X[104X
    [4X[28X<empty partial perm>[128X[104X
  [4X[32X[104X
  
  
  [1X54.4 [33X[0;0YChanging the representation of a partial permutation[133X[101X
  
  [33X[0;0YIt is possible that a partial permutation in [5XGAP[105X can be represented by other
  types  of  objects, or that other types of [5XGAP[105X objects can be represented by
  partial   permutations.   Partial   permutations  which  are  mathematically
  permutations  can  be  converted into permutations in [5XGAP[105X using the function
  [2XAsPermutation[102X  ([14X42.5-5[114X).  Similarly,  a partial permutation can be converted
  into a transformation using [2XAsTransformation[102X ([14X53.3-1[114X).[133X
  
  [33X[0;0YIn  this section we describe functions for converting other types of objects
  in [5XGAP[105X into partial permutations.[133X
  
  [1X54.4-1 AsPartialPerm[101X
  
  [29X[2XAsPartialPerm[102X( [3Xf[103X, [3Xset[103X ) [32X function
  [29X[2XAsPartialPerm[102X( [3Xf[103X ) [32X function
  [29X[2XAsPartialPerm[102X( [3Xf[103X, [3Xn[103X ) [32X function
  [6XReturns:[106X  [33X[0;10YA partial permutation.[133X
  
  [33X[0;0YA  permutation  [3Xf[103X defines a partial permutation when it is restricted to any
  finite  set  of  positive integers. [10XAsPartialPerm[110X can be used to obtain this
  partial permutation.[133X
  
  [33X[0;0YThere are several possible arguments for [10XAsPartialPerm[110X:[133X
  
  [8Xfor a permutation and set of positive integers[108X
        [33X[0;6Y[10XAsPartialPerm[110X returns the partial permutation that equals [3Xf[103X on the set
        of positive integers [3Xset[103X and that is undefined on every other positive
        integer.[133X
  
        [33X[0;6YNote  that as explained in [2XPartialPerm[102X ([14X54.2-1[114X) [13Xa permutation is never
        a  partial  permutation[113X  in  [5XGAP[105X,  please keep this in mind when using
        [10XAsPartialPerm[110X.[133X
  
  [8Xfor a permutation[108X
        [33X[0;6Y[10XAsPartialPerm[110X  returns  the  partial permutation that agrees with [3Xf[103X on
        [10X[1..LargestMovedPoint([3Xf[103X[10X)][110X  and  that  is  not  defined  on  any  other
        positive integer.[133X
  
  [8Xfor a permutation and a positive integer[108X
        [33X[0;6Y[10XAsPartialPerm[110X  returns  the  partial permutation that agrees with [3Xf[103X on
        [10X[1..[3Xn[103X[10X][110X,  when  [3Xn[103X is a positive integer, and that is not defined on any
        other positive integer.[133X
  
  [33X[0;0YThe   operation   [2XPartialPermOp[102X   ([14X54.2-2[114X)  can  also  be  used  to  convert
  permutations into partial permutations.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=(2,8,19,9,14,10,20,17,4,13,12,3,5,7,18,16);;[127X[104X
    [4X[25Xgap>[125X [27XAsPartialPerm(f);[127X[104X
    [4X[28X(1)(2,8,19,9,14,10,20,17,4,13,12,3,5,7,18,16)(6)(11)(15)[128X[104X
    [4X[25Xgap>[125X [27XAsPartialPerm(f, [ 1, 2, 3 ] );[127X[104X
    [4X[28X[2,8][3,5](1)[128X[104X
  [4X[32X[104X
  
  [1X54.4-2 AsPartialPerm[101X
  
  [29X[2XAsPartialPerm[102X( [3Xf[103X, [3Xset[103X ) [32X function
  [29X[2XAsPartialPerm[102X( [3Xf[103X, [3Xn[103X ) [32X function
  [29X[2XAsPartialPerm[102X( [3Xf[103X ) [32X function
  [6XReturns:[106X  [33X[0;10YA partial permutation or [9Xfail[109X.[133X
  
  [33X[0;0YA  transformation [3Xf[103X defines a partial permutation when it is restricted to a
  set of positive integers where it is injective. [10XAsPartialPerm[110X can be used to
  obtain this partial permutation.[133X
  
  [33X[0;0YThere are several possible arguments for [10XAsPartialPerm[110X:[133X
  
  [8Xfor a transformation and set of positive integers[108X
        [33X[0;6Y[10XAsPartialPerm[110X  returns the partial permutation obtained by restricting
        [3Xf[103X to the set of positive integers [3Xset[103X when:[133X
  
        [30X    [33X[0;12Y[3Xset[103X contains no elements exceeding the degree of [3Xf[103X;[133X
  
        [30X    [33X[0;12Y[3Xf[103X is injective on [3Xset[103X.[133X
  
  [8Xfor a transformation and a positive integer[108X
        [33X[0;6Y[10XAsPartialPerm[110X  returns  the  partial permutation that agrees with [3Xf[103X on
        [10X[1..[3Xn[103X[10X][110X  when  [3XA[103X  is  a  positive  integer  and  this set satisfies the
        conditions given above.[133X
  
  [8Xfor a transformation[108X
        [33X[0;6YLet  [10Xn[110X  denote the degree of [3Xf[103X. If [10Xn^[3Xf[103X[10X=n[110X and [3Xf[103X is injective on those [10Xi[110X
        such  that  [10Xi^[3Xf[103X[10X<>n[110X, then [10XAsPartialPerm[110X returns the partial permutation
        obtained by restricting [3Xf[103X to those [10Xi[110X such that [10Xi^[3Xf[103X[10X<>n[110X.[133X
  
  [33X[0;0Y[10XAsPartialPerm[110X  returns  [9Xfail[109X  if  the  arguments  do  not describe a partial
  permutation.[133X
  
  [33X[0;0YThe   operation   [2XPartialPermOp[102X   ([14X54.2-2[114X)  can  also  be  used  to  convert
  transformations into partial permutations.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=Transformation( [ 8, 3, 5, 9, 6, 2, 9, 7, 9 ] );;[127X[104X
    [4X[25Xgap>[125X [27XAsPartialPerm(f);[127X[104X
    [4X[28X[1,8,7](2,3,5,6)[128X[104X
    [4X[25Xgap>[125X [27XAsPartialPerm(f, 3);[127X[104X
    [4X[28X[1,8][2,3,5][128X[104X
    [4X[25Xgap>[125X [27XAsPartialPerm(f, [ 2 .. 4 ] );[127X[104X
    [4X[28X[2,3,5][4,9][128X[104X
    [4X[25Xgap>[125X [27Xf:=Transformation( [ 2, 10, 2, 4, 4, 7, 6, 9, 10, 1 ] );;[127X[104X
    [4X[25Xgap>[125X [27XAsPartialPerm(f);[127X[104X
    [4X[28Xfail[128X[104X
  [4X[32X[104X
  
  
  [1X54.5 [33X[0;0YOperators and operations for partial permutations[133X[101X
  
  [8X[10X[3Xf[103X[10X ^ -1[110X[108X
        [33X[0;6Yreturns the inverse of the partial permutation [3Xf[103X.[133X
  
  [8X[10X[3Xi[103X[10X ^ [3Xf[103X[10X[110X[108X
        [33X[0;6Yreturns  the  image  of  the  positive  integer  [3Xi[103X  under  the partial
        permutation [3Xf[103X if it is defined and [10X0[110X if it is not.[133X
  
  [8X[10X[3Xi[103X[10X / [3Xf[103X[10X[110X[108X
        [33X[0;6Yreturns  the  preimage  of  the  positive  integer [3Xi[103X under the partial
        permutation  [3Xf[103X  if  it  is  defined  and [10X0[110X if it is not. Note that the
        inverse of [3Xf[103X is not calculated to find the preimage of [3Xi[103X.[133X
  
  [8X[10X[3Xf[103X[10X ^ [3Xg[103X[10X[110X[108X
        [33X[0;6Yreturns  [10X[3Xg[103X[10X^-1*[3Xf[103X[10X*[3Xg[103X[10X[110X  when  [3Xf[103X  is  a  partial  permutation  and  [3Xg[103X  is  a
        permutation  or  partial permutation; see [2X\^[102X ([14X31.12-1[114X). This operation
        requires  essentially  the same number of steps as multiplying partial
        permutations,  which  is  around  one  third  as many as inverting and
        multiplying twice.[133X
  
  [8X[10X[3Xf[103X[10X * [3Xg[103X[10X[110X[108X
        [33X[0;6Yreturns  the  composition  of  [3Xf[103X  and  [3Xg[103X  when  [3Xf[103X  and  [3Xg[103X  are partial
        permutations  or  permutations.  The  product  of  a permutation and a
        partial permutation is returned as a partial permutation.[133X
  
  [8X[10X[3Xf[103X[10X / [3Xg[103X[10X[110X[108X
        [33X[0;6Yreturns  [10X[3Xf[103X[10X*[3Xg[103X[10X^-1[110X when [3Xf[103X is a partial permutation and [3Xg[103X is a permutation
        or  partial  permutation. This operation requires essentially the same
        number   of  steps  as  multiplying  partial  permutations,  which  is
        approximately  half  that required to first invert [3Xg[103X and then take the
        produce with [3Xf[103X.[133X
  
  [8X[10XLQUO([3Xg[103X[10X, [3Xf[103X[10X)[110X[108X
        [33X[0;6Yreturns  [10X[3Xg[103X[10X^-1*[3Xf[103X[10X[110X when [3Xf[103X is a partial permutation and [3Xg[103X is a permutation
        or  partial  permutation. This operation requires essentially the same
        number   of  steps  as  multiplying  partial  permutations,  which  is
        approximately  half  that required to first invert [3Xg[103X and then take the
        produce with [3Xf[103X.[133X
  
  [8X[10X[3Xf[103X[10X < [3Xg[103X[10X[110X[108X
        [33X[0;6Yreturns  [9Xtrue[109X if the image of [3Xf[103X on the range from 1 to the degree of [3Xf[103X
        is lexicographically less than the corresponding image for [3Xg[103X and [9Xfalse[109X
        if    it    is    not.    See   [2XNaturalLeqPartialPerm[102X   ([14X54.5-4[114X)   and
        [2XShortLexLeqPartialPerm[102X  ([14X54.5-5[114X)  for  additional  orders  for partial
        permutations.[133X
  
  [8X[10X[3Xf[103X[10X = [3Xg[103X[10X[110X[108X
        [33X[0;6Yreturns   [9Xtrue[109X  if  the  partial  permutation  [3Xf[103X  equals  the  partial
        permutation [3Xg[103X and returns [9Xfalse[109X if it does not.[133X
  
  [1X54.5-1 PermLeftQuoPartialPerm[101X
  
  [29X[2XPermLeftQuoPartialPerm[102X( [3Xf[103X, [3Xg[103X ) [32X operation
  [29X[2XPermLeftQuoPartialPermNC[102X( [3Xf[103X, [3Xg[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA permutation.[133X
  
  [33X[0;0YReturns  the  permutation  on  the image set of [3Xf[103X induced by [10X[3Xf[103X[10X^-1*[3Xg[103X[10X[110X when the
  partial permutations [3Xf[103X and [3Xg[103X have equal domain and image set.[133X
  
  [33X[0;0Y[10XPermLeftQuoPartialPerm[110X  verifies  that  [3Xf[103X and [3Xg[103X have equal domains and image
  sets,  and returns an error if they do not. [10XPermLeftQuoPartialPermNC[110X does no
  checks.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 5, 7 ], [ 7, 9, 10, 4, 2, 5 ] );[127X[104X
    [4X[28X[1,7,5,2,9][3,10](4)[128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 1, 2, 3, 4, 5, 7 ], [ 7, 4, 9, 2, 5, 10 ] );[127X[104X
    [4X[28X[1,7,10][3,9](2,4)(5)[128X[104X
    [4X[25Xgap>[125X [27XPermLeftQuoPartialPerm(f, g);[127X[104X
    [4X[28X(2,5,10,9,4)[128X[104X
  [4X[32X[104X
  
  [1X54.5-2 PreImagePartialPerm[101X
  
  [29X[2XPreImagePartialPerm[102X( [3Xf[103X, [3Xi[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA positive integer or [9Xfail[109X.[133X
  
  [33X[0;0Y[10XPreImagePartialPerm[110X returns the preimage of the positive integer [3Xi[103X under the
  partial  permutation  [3Xf[103X if [3Xi[103X belongs to the image of [3Xf[103X. If [3Xi[103X does not belong
  to the image of [3Xf[103X, then [9Xfail[109X is returned.[133X
  
  [33X[0;0YThe same result can be obtained by using [10X[3Xi[103X[10X/[3Xf[103X[10X[110X as described in Section [14X54.5[114X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 5, 9, 10 ], [ 5, 10, 7, 8, 9, 1 ] );[127X[104X
    [4X[28X[2,10,1,5,8][3,7](9)[128X[104X
    [4X[25Xgap>[125X [27XPreImagePartialPerm(f, 8);[127X[104X
    [4X[28X5[128X[104X
    [4X[25Xgap>[125X [27XPreImagePartialPerm(f, 5);[127X[104X
    [4X[28X1[128X[104X
    [4X[25Xgap>[125X [27XPreImagePartialPerm(f, 1);[127X[104X
    [4X[28X10[128X[104X
    [4X[25Xgap>[125X [27XPreImagePartialPerm(f, 10);[127X[104X
    [4X[28X2[128X[104X
    [4X[25Xgap>[125X [27XPreImagePartialPerm(f, 2); [127X[104X
    [4X[28Xfail[128X[104X
  [4X[32X[104X
  
  [1X54.5-3 ComponentPartialPermInt[101X
  
  [29X[2XComponentPartialPermInt[102X( [3Xf[103X, [3Xi[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YA set of positive integers.[133X
  
  [33X[0;0Y[10XComponentPartialPermInt[110X   returns   the  elements  of  the  component  of  [3Xf[103X
  containing [3Xi[103X that can be obtained by repeatedly applying [3Xf[103X to [3Xi[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 4, 5, 6, 7, 8, 10, 14, 15, 16, 17, 18 ], [127X[104X
    [4X[25X>[125X [27X[ 11, 4, 14, 16, 15, 3, 20, 8, 17, 19, 1, 6, 12 ] );[127X[104X
    [4X[28X[2,4,14,17,6,15,19][5,16,1,11][7,3][10,8,20][18,12][128X[104X
    [4X[25Xgap>[125X [27XComponentPartialPermInt(f, 4);[127X[104X
    [4X[28X[ 4, 14, 17, 6, 15, 19 ][128X[104X
    [4X[25Xgap>[125X [27XComponentPartialPermInt(f, 3);[127X[104X
    [4X[28X[  ][128X[104X
    [4X[25Xgap>[125X [27XComponentPartialPermInt(f, 10);[127X[104X
    [4X[28X[ 10, 8, 20 ][128X[104X
    [4X[25Xgap>[125X [27XComponentPartialPermInt(f, 100);[127X[104X
    [4X[28X[  ][128X[104X
  [4X[32X[104X
  
  [1X54.5-4 NaturalLeqPartialPerm[101X
  
  [29X[2XNaturalLeqPartialPerm[102X( [3Xf[103X, [3Xg[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Y[9Xtrue[109X or [9Xfalse[109X.[133X
  
  [33X[0;0YThe  [13Xnatural  partial order[113X [22X≤[122X on an inverse semigroup [10XS[110X is defined by [10Xs[110X[22X≤[122X[10Xt[110X if
  there  exists  an  idempotent  [10Xe[110X  in  [10XS[110X such that [10Xs=et[110X. Hence if [3Xf[103X and [3Xg[103X are
  partial  permutations,  then [3Xf[103X[22X≤[122X[3Xg[103X if and only if [3Xf[103X is a restriction of [3Xg[103X; see
  [2XRestrictedPartialPerm[102X ([14X54.2-3[114X).[133X
  
  [33X[0;0Y[10XNaturalLeqPartialPerm[110X  returns  [9Xtrue[109X if [3Xf[103X is a restriction of [3Xg[103X and [9Xfalse[109X if
  it is not. Note that since this is a partial order and not a total order, it
  is  possible  that  [3Xf[103X  and  [3Xg[103X  are  incomparable with respect to the natural
  partial order.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 16, 17, 18, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 3, 12, 14, 4, 11, 18, 17, 2, 9, 5, 15, 8, 20, 10, 19 ] );;[127X[104X
    [4X[25Xgap>[125X [27Xg:=RestrictedPartialPerm(f, [ 1, 2, 3, 9, 13, 20 ] );[127X[104X
    [4X[28X[1,3,14][2,12][128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(g,f);[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(f,g);[127X[104X
    [4X[28Xfalse[128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 1, 2, 3, 4, 5, 8, 10 ], [127X[104X
    [4X[25X>[125X [27X[ 7, 1, 4, 3, 2, 6, 5 ] );;[127X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(f, g);[127X[104X
    [4X[28Xfalse[128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(g, f);[127X[104X
    [4X[28Xfalse[128X[104X
  [4X[32X[104X
  
  [1X54.5-5 ShortLexLeqPartialPerm[101X
  
  [29X[2XShortLexLeqPartialPerm[102X( [3Xf[103X, [3Xg[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Y[9Xtrue[109X or [9Xfalse[109X.[133X
  
  [33X[0;0Y[10XShortLexLeqPartialPerm[110X  returns  [9Xtrue[109X if the concatenation of the domain and
  image list of [3Xf[103X is short-lex less than the corresponding concatenation for [3Xg[103X
  and [9Xfalse[109X otherwise.[133X
  
  [33X[0;0YNote  that  this  is not the natural partial order on partial permutation or
  the same as comparing [3Xf[103X and [3Xg[103X using [10X\<[110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 4, 6, 7, 8, 10 ], [127X[104X
    [4X[25X>[125X [27X[ 3, 8, 1, 9, 4, 10, 5, 6 ] );[127X[104X
    [4X[28X[2,8,5][7,10,6,4,9](1,3)[128X[104X
    [4X[25Xgap>[125X [27Xg:=PartialPerm( [ 1, 2, 3, 4, 5, 8, 10 ], [127X[104X
    [4X[25X>[125X [27X[ 7, 1, 4, 3, 2, 6, 5 ] );[127X[104X
    [4X[28X[8,6][10,5,2,1,7](3,4)[128X[104X
    [4X[25Xgap>[125X [27Xf<g;[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27Xg<f;[127X[104X
    [4X[28Xfalse[128X[104X
    [4X[25Xgap>[125X [27XShortLexLeqPartialPerm(f, g);[127X[104X
    [4X[28Xfalse[128X[104X
    [4X[25Xgap>[125X [27XShortLexLeqPartialPerm(g, f);[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(f, g);[127X[104X
    [4X[28Xfalse[128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(g, f);[127X[104X
    [4X[28Xfalse[128X[104X
  [4X[32X[104X
  
  [1X54.5-6 TrimPartialPerm[101X
  
  [29X[2XTrimPartialPerm[102X( [3Xf[103X ) [32X function
  [6XReturns:[106X  [33X[0;10YNothing.[133X
  
  [33X[0;0YIt can happen that the internal representation of a partial permutation uses
  more  memory than necessary. For example, by composing a partial permutation
  with  codegree  less  than  65536  with  a partial permutation with codegree
  greater  than 65535. It is possible that the resulting partial permutation [3Xf[103X
  has  its  codegree  and  images stored as 32-bit integers, while none of its
  image  points  exceeds  65536. The purpose of this function is to change the
  internal  representation  of  such  an  [3Xf[103X  from using 32-bit to using 16-bit
  integers.[133X
  
  [33X[0;0YNote  that  the  partial  permutation  [3Xf[103X is changed in-place, and nothing is
  returned by this function.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2 ], [ 3, 4 ] )[127X[104X
    [4X[25X>[125X [27X*PartialPerm( [ 3, 5 ], [ 3, 100000 ] );[127X[104X
    [4X[28X[1,3][128X[104X
    [4X[25Xgap>[125X [27XIsPPerm4Rep(f);[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XTrimPartialPerm(f); f;[127X[104X
    [4X[28X[1,3][128X[104X
    [4X[25Xgap>[125X [27XIsPPerm4Rep(f);[127X[104X
    [4X[28Xfalse[128X[104X
  [4X[32X[104X
  
  
  [1X54.6 [33X[0;0YDisplaying partial permutations[133X[101X
  
  [33X[0;0YIt  is  possible  to  change  the way that [5XGAP[105X displays partial permutations
  using      the      user     preferences     [10XPartialPermDisplayLimit[110X     and
  [10XNotationForPartialPerms[110X;   see   Section  [2XUserPreference[102X  ([14X3.2-3[114X)  for  more
  information about user preferences.[133X
  
  [33X[0;0YIf  [10Xf[110X  is  a  partial  permutation of rank [10Xr[110X exceeding the value of the user
  preference [10XPartialPermDisplayLimit[110X, then [10Xf[110X is displayed as:[133X
  
  [4X[32X  Example  [32X[104X
    [4X[28X<partial perm on r pts with degree m, codegree n>[128X[104X
  [4X[32X[104X
  
  [33X[0;0Ywhere  the  degree  and  codegree  are [10Xm[110X and [10Xn[110X, respectively. The idea is to
  abbreviated  the display of partial permutations defined on many points. The
  default value for the [10XPartialPermDisplayLimit[110X is [10X100[110X.[133X
  
  [33X[0;0YIf  the rank of [10Xf[110X does not exceed the value of [10XPartialPermDisplayLimit[110X, then
  how   [10Xf[110X   is   displayed  depends  on  the  value  of  the  user  preference
  [10XNotationForPartialPerms[110X  except  in  the  case  that  [10Xf[110X is the empty partial
  permutation or an identity partial permutation.[133X
  
  [33X[0;0YThere are three possible values for [10XNotationForPartialPerms[110X user preference,
  which are described below.[133X
  
  [8Xcomponent[108X
        [33X[0;6YSimilar   to   permutations,   and   unlike  transformations,  partial
        permutations can be expressed as products of disjoint permutations and
        chains. A [13Xchain[113X is a list [10Xc[110X of some length [10Xn[110X such that:[133X
  
        [30X    [33X[0;12Y[10Xc[1][110X is an element of the domain of [3Xf[103X but not the image[133X
  
        [30X    [33X[0;12Y[10Xc[i]^[3Xf[103X[10X=c[i+1][110X for all [10Xi[110X in the range from [10X1[110X to [10Xn-1[110X.[133X
  
        [30X    [33X[0;12Y[10Xc[n][110X is in the image of [3Xf[103X but not the domain.[133X
  
        [33X[0;6YIn the display, permutations are displayed as they usually are in [5XGAP[105X,
        except that fixed points are displayed enclosed in round brackets, and
        chains are displayed enclosed in square brackets.[133X
  
  [4X      [32X  Example  [32X[104X
          [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
          [4X[25X>[125X [27X[ 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 16, 17, 18, 19 ],[127X[104X
          [4X[25X>[125X [27X[ 3, 12, 14, 4, 11, 18, 17, 2, 9, 5, 15, 8, 20, 10, 19 ]);;[127X[104X
          [4X[25Xgap>[125X [27XPrettyPrintPP(f);[127X[104X
          [4X[28X[1,3,14][16,8,2,12,15](4)(5,11)[6,18,10,9][7,17,20](19)[128X[104X
        [4X[32X[104X
  
        [33X[0;6YThis  option  is the most compact way to display a partial permutation
        and    is    the    default    value    of    the    user   preference
        [10XNotationForPartialPerms[110X.[133X
  
  [8Xdomainimage[108X
        [33X[0;6YWith  this  option a partial permutation [10Xf[110X is displayed in the format:
        [10XDomainOfPartialPerm([3Xf[103X[10X)-> ImageListOfPartialPerm([3Xf[103X[10X)[110X.[133X
  
  [4X      [32X  Example  [32X[104X
          [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 4, 5, 6, 7 ], [ 10, 1, 6, 5, 8, 7 ]);[127X[104X
          [4X[28X[ 1, 2, 4, 5, 6, 7 ] -> [ 10, 1, 6, 5, 8, 7 ][128X[104X
        [4X[32X[104X
  
  [8Xinput[108X
        [33X[0;6YWith   this   option   a   partial  permutation  [3Xf[103X  is  displayed  as:
        [10XPartialPerm(DomainOfPartialPerm([3Xf[103X[10X),  ImageListOfPartialPerm([3Xf[103X[10X))[110X  which
        corresponds  to  the input (of the first type described in [2XPartialPerm[102X
        ([14X54.2-1[114X)).[133X
  
  [4X      [32X  Example  [32X[104X
          [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 5, 6, 9, 10 ], [127X[104X
          [4X[25X>[125X [27X[ 4, 7, 3, 8, 2, 1, 6 ] );[127X[104X
          [4X[28XPartialPerm( [ 1, 2, 3, 5, 6, 9, 10 ], [ 4, 7, 3, 8, 2, 1, 6 ] )[128X[104X
        [4X[32X[104X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XSetUserPreference("PartialPermDisplayLimit", 12);                [127X[104X
    [4X[25Xgap>[125X [27XUserPreference("PartialPermDisplayLimit");[127X[104X
    [4X[28X12[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm([1,2,3,4,5,6], [6,7,1,4,3,2]);[127X[104X
    [4X[28X[5,3,1,6,2,7](4)[128X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [127X[104X
    [4X[25X>[125X [27X[ 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 16, 17, 18, 19 ], [127X[104X
    [4X[25X>[125X [27X[ 3, 12, 14, 4, 11, 18, 17, 2, 9, 5, 15, 8, 20, 10, 19 ] );[127X[104X
    [4X[28X<partial perm on 15 pts with degree 19, codegree 20>[128X[104X
    [4X[25Xgap>[125X [27XSetUserPreference("PartialPermDisplayLimit", 100);[127X[104X
    [4X[25Xgap>[125X [27Xf;[127X[104X
    [4X[28X[1,3,14][6,18,10,9][7,17,20][16,8,2,12,15](4)(5,11)(19)[128X[104X
    [4X[25Xgap>[125X [27XUserPreference("NotationForPartialPerms");[127X[104X
    [4X[28X"component"[128X[104X
    [4X[25Xgap>[125X [27XSetUserPreference("NotationForPartialPerms", "domainimage");[127X[104X
    [4X[25Xgap>[125X [27Xf;[127X[104X
    [4X[28X[ 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 16, 17, 18, 19 ] -> [128X[104X
    [4X[28X[ 3, 12, 14, 4, 11, 18, 17, 2, 9, 5, 15, 8, 20, 10, 19 ][128X[104X
    [4X[25Xgap>[125X [27XSetUserPreference("NotationForPartialPerms", "input");[127X[104X
    [4X[25Xgap>[125X [27Xf;[127X[104X
    [4X[28XPartialPerm( [128X[104X
    [4X[28X[ 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 16, 17, 18, 19 ], [128X[104X
    [4X[28X[ 3, 12, 14, 4, 11, 18, 17, 2, 9, 5, 15, 8, 20, 10, 19 ] )[128X[104X
  [4X[32X[104X
  
  
  [1X54.7 [33X[0;0YSemigroups and inverse semigroups of partial permutations[133X[101X
  
  [33X[0;0YAs  mentioned  at  the  start  of  the  chapter,  every inverse semigroup is
  isomorphic  to  a  semigroup of partial permutations, and in this section we
  describe the functions in [5XGAP[105X specific to partial perms semigroups. For more
  information about semigroups and inverse semigroups see Chapter [14X51[114X.[133X
  
  [33X[0;0YThe  [5XSemigroups[105X  package  contains many additional functions and methods for
  computing with semigroups of partial permutations. In particular, [5XSemigroups[105X
  contains more efficient methods than those available in the [5XGAP[105X library (and
  in  many  cases  more  efficient  than  any  other  software)  for  creating
  semigroups  of  transformations,  calculating  their  Green's classes, size,
  elements,  group  of  units,  minimal  ideal, small generating sets, testing
  membership,  finding the inverses of a regular element, factorizing elements
  over the generators, and more.[133X
  
  [33X[0;0YSince  a  partial  permutation  semigroup  is  also  a  partial  permutation
  collection,  there  are  special  methods  for [2XDomainOfPartialPermCollection[102X
  ([14X54.3-4[114X),  [2XImageOfPartialPermCollection[102X  ([14X54.3-5[114X),  [2XFixedPointsOfPartialPerm[102X
  ([14X54.3-8[114X),   [2XMovedPoints[102X  ([14X54.3-9[114X),  [2XNrFixedPoints[102X  ([14X54.3-10[114X),  [2XNrMovedPoints[102X
  ([14X54.3-11[114X),  [2XLargestMovedPoint[102X  ([14X54.3-13[114X),  and  [2XSmallestMovedPoint[102X ([14X54.3-12[114X)
  when applied to a partial permutation semigroup.[133X
  
  [1X54.7-1 IsPartialPermSemigroup[101X
  
  [29X[2XIsPartialPermSemigroup[102X( [3Xobj[103X ) [32X property
  [29X[2XIsPartialPermMonoid[102X( [3Xobj[103X ) [32X property
  [6XReturns:[106X  [33X[0;10Y[9Xtrue[109X or [9Xfalse[109X.[133X
  
  [33X[0;0YA  [13Xpartial  perm  semigroup[113X  is  simply  a  semigroup  consisting of partial
  permutations, which may or may not be an inverse semigroup. An object [3Xobj[103X in
  [5XGAP[105X  is  a  partial  perm  semigroup if and only if it satisfies [2XIsSemigroup[102X
  ([14X51.1-1[114X) and [2XIsPartialPermCollection[102X ([14X54.1-2[114X).[133X
  
  [33X[0;0YA  [13Xpartial  perm  monoid[113X  is a monoid consisting of partial permutations. An
  object in [5XGAP[105X is a partial perm monoid if it satisfies [2XIsMonoid[102X ([14X51.2-1[114X) and
  [2XIsPartialPermCollection[102X ([14X54.1-2[114X).[133X
  
  [33X[0;0YNote   that  it  is  possible  for  a  partial  perm  semigroup  to  have  a
  multiplicative neutral element (i.e. an identity element) but not to satisfy
  [10XIsPartialPermMonoid[110X. For example,[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf:=PartialPerm( [ 1, 2, 3, 6, 8, 10 ], [ 2, 6, 7, 9, 1, 5 ] );;[127X[104X
    [4X[25Xgap>[125X [27XS:=Semigroup(f, One(f));[127X[104X
    [4X[28X<commutative partial perm monoid on 9 pts with 1 generator>[128X[104X
    [4X[25Xgap>[125X [27XIsMonoid(S);[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XIsPartialPermMonoid(S);[127X[104X
    [4X[28Xtrue[128X[104X
  [4X[32X[104X
  
  [33X[0;0YNote  that  unlike transformation semigroups, the [2XOne[102X ([14X31.10-2[114X) of a partial
  permutation semigroup must coincide with the multiplicative neutral element,
  if either exists.[133X
  
  [33X[0;0YFor more details see [2XIsMagmaWithOne[102X ([14X35.1-2[114X).[133X
  
  [1X54.7-2 DegreeOfPartialPermSemigroup[101X
  
  [29X[2XDegreeOfPartialPermSemigroup[102X( [3XS[103X ) [32X attribute
  [29X[2XCodegreeOfPartialPermSemigroup[102X( [3XS[103X ) [32X attribute
  [29X[2XRankOfPartialPermSemigroup[102X( [3XS[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YA non-negative integer.[133X
  
  [33X[0;0YThe [13Xdegree[113X of a partial permutation semigroup [3XS[103X is the largest degree of any
  partial permutation in [3XS[103X.[133X
  
  [33X[0;0YThe  [13Xcodegree[113X  of  a partial permutation semigroup [3XS[103X is the largest positive
  integer in its image.[133X
  
  [33X[0;0YThe  [13Xrank[113X  of  a  partial permutation semigroup [3XS[103X is the number of points on
  which it acts.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=Semigroup( PartialPerm( [ 1, 2 ], [ 10000, 3 ] ) );[127X[104X
    [4X[28X<commutative partial perm semigroup on 2 pts with 1 generator>[128X[104X
    [4X[25Xgap>[125X [27XDegreeOfPartialPermSemigroup(S);[127X[104X
    [4X[28X2[128X[104X
    [4X[25Xgap>[125X [27XCodegreeOfPartialPermSemigroup(S);[127X[104X
    [4X[28X10000[128X[104X
    [4X[25Xgap>[125X [27XRankOfPartialPermSemigroup(S);[127X[104X
    [4X[28X2[128X[104X
  [4X[32X[104X
  
  [1X54.7-3 SymmetricInverseSemigroup[101X
  
  [29X[2XSymmetricInverseSemigroup[102X( [3Xn[103X ) [32X operation
  [29X[2XSymmetricInverseMonoid[102X( [3Xn[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YThe symmetric inverse semigroup of degree [3Xn[103X.[133X
  
  [33X[0;0YIf  [3Xn[103X  is a non-negative integer, then [10XSymmetricInverseSemigroup[110X returns the
  inverse  semigroup  consisting  of  all partial permutations with degree and
  codegree at most [3Xn[103X. Note that [3Xn[103X must be non-negative, but in particular, can
  equal [10X0[110X.[133X
  
  [33X[0;0YThe  symmetric  inverse  semigroup  is  generated by any set that of partial
  permutations  that  generate the symmetric group on [3Xn[103X points and any partial
  permutation of rank [10X[3Xn[103X[10X-1[110X.[133X
  
  [33X[0;0Y[10XSymmetricInverseMonoid[110X is a synonym for [10XSymmetricInverseSemigroup[110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=SymmetricInverseSemigroup(5);[127X[104X
    [4X[28X<symmetric inverse semigroup on 5 pts>[128X[104X
    [4X[25Xgap>[125X [27XSize(S);[127X[104X
    [4X[28X1546[128X[104X
  [4X[32X[104X
  
  [1X54.7-4 IsSymmetricInverseSemigroup[101X
  
  [29X[2XIsSymmetricInverseSemigroup[102X( [3XS[103X ) [32X property
  [29X[2XIsSymmetricInverseMonoid[102X( [3XS[103X ) [32X property
  [6XReturns:[106X  [33X[0;10Y[9Xtrue[109X or [9Xfalse[109X.[133X
  
  [33X[0;0YIf  the  partial  perm  semigroup  [3XS[103X  of  degree  and  codegree [3Xn[103X equals the
  symmetric  inverse  semigroup  on [3Xn[103X points, then [10XIsSymmetricInverseSemigroup[110X
  return [9Xtrue[109X and otherwise it returns [9Xfalse[109X.[133X
  
  [33X[0;0Y[10XIsSymmetricInverseMonoid[110X  is a synonym of [10XIsSymmetricInverseSemigroup[110X. It is
  common  in the literature for the symmetric inverse monoid to be referred to
  as the symmetric inverse semigroup.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=Semigroup( AsPartialPerm((1,3,4,2), 5), AsPartialPerm((1,3,5), 5),[127X[104X
    [4X[25X>[125X [27XPartialPerm( [ 1, 2, 3, 4 ] ) );[127X[104X
    [4X[28X<partial perm semigroup on 5 pts with 3 generators>[128X[104X
    [4X[25Xgap>[125X [27XIsSymmetricInverseSemigroup(S);[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XS;[127X[104X
    [4X[28X<symmetric inverse semigroup on 5 pts>[128X[104X
  [4X[32X[104X
  
  [1X54.7-5 NaturalPartialOrder[101X
  
  [29X[2XNaturalPartialOrder[102X( [3XS[103X ) [32X attribute
  [29X[2XReverseNaturalPartialOrder[102X( [3XS[103X ) [32X attribute
  [6XReturns:[106X  [33X[0;10YThe natural partial order on an inverse semigroup.[133X
  
  [33X[0;0YThe  [13Xnatural  partial order[113X [22X≤[122X on an inverse semigroup [3XS[103X is defined by [10Xs[110X[22X≤[122X[10Xt[110X if
  there  exists  an  idempotent  [10Xe[110X  in  [3XS[103X such that [10Xs=et[110X. Hence if [10Xf[110X and [10Xg[110X are
  partial  permutations,  then [10Xf[110X[22X≤[122X[10Xg[110X if and only if [10Xf[110X is a restriction of [10Xg[110X; see
  [2XRestrictedPartialPerm[102X ([14X54.2-3[114X).[133X
  
  [33X[0;0Y[10XNaturalPartialOrder[110X  returns  the  natural  partial  order  on  the  inverse
  semigroup  of  partial permutations [3XS[103X as a list of sets of positive integers
  where  entry  [10Xi[110X  in  [10XNaturalPartialOrder([3XS[103X[10X)[110X  is  the  set  of  positions  in
  [10XElements([3XS[103X[10X)[110X  of  elements  which  are  less  than  [10XElements([3XS[103X[10X)[i][110X.  See also
  [2XNaturalLeqPartialPerm[102X ([14X54.5-4[114X).[133X
  
  [33X[0;0Y[10XReverseNaturalPartialOrder[110X  returns the reverse of the natural partial order
  on  the  inverse  semigroup  of  partial permutations [3XS[103X as a list of sets of
  positive  integers where entry [10Xi[110X in [10XReverseNaturalPartialOrder([3XS[103X[10X)[110X is the set
  of   positions   in   [10XElements([3XS[103X[10X)[110X   of   elements  which  are  greater  than
  [10XElements([3XS[103X[10X)[i][110X. See also [2XNaturalLeqPartialPerm[102X ([14X54.5-4[114X).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=InverseSemigroup([ PartialPerm( [ 1, 3 ], [ 1, 3 ] ),[127X[104X
    [4X[25X>[125X [27XPartialPerm( [ 1, 2 ], [ 3, 2 ] ) ] );[127X[104X
    [4X[28X<inverse partial perm semigroup on 3 pts with 2 generators>[128X[104X
    [4X[25Xgap>[125X [27XSize(S);[127X[104X
    [4X[28X11[128X[104X
    [4X[25Xgap>[125X [27XNaturalPartialOrder(S);[127X[104X
    [4X[28X[ [  ], [ 1 ], [ 1 ], [ 1 ], [ 1, 2, 4 ], [ 1, 3, 4 ], [ 1 ], [ 1 ], [128X[104X
    [4X[28X  [ 1, 4, 7 ], [ 1, 4, 8 ], [ 1, 2, 8 ] ][128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(Elements(S)[4], Elements(S)[10]);[127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XNaturalLeqPartialPerm(Elements(S)[4], Elements(S)[1]); [127X[104X
    [4X[28Xfalse[128X[104X
  [4X[32X[104X
  
  [1X54.7-6 IsomorphismPartialPermMonoid[101X
  
  [29X[2XIsomorphismPartialPermMonoid[102X( [3XS[103X ) [32X operation
  [29X[2XIsomorphismPartialPermSemigroup[102X( [3XS[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10YAn isomorphism.[133X
  
  [33X[0;0Y[10XIsomorphismPartialPermSemigroup([3XS[103X[10X)[110X  returns  an isomorphism from the inverse
  semigroup or group [3XS[103X to an inverse semigroup of partial permutations.[133X
  
  [33X[0;0Y[10XIsomorphismPartialPermMonoid([3XS[103X[10X)[110X  returns  an  isomorphism  from  the inverse
  monoid or group [3XS[103X to an inverse monoid of partial permutations.[133X
  
  [33X[0;0YWe  only describe [10XIsomorphismPartialPermMonoid[110X, the corresponding statements
  for [10XIsomorphismPartialPermSemigroup[110X also hold.[133X
  
  [8XPartial permutation semigroups[108X
        [33X[0;6YIf [3XS[103X is a partial permutation semigroup that does not satisfy [2XIsMonoid[102X
        ([14XReference: IsMonoid[114X) but where [10XMultiplicativeNeutralElement([3XS[103X[10X)<>fail[110X,
        then  [10XIsomorphismPartialPermMonoid([3XS[103X[10X)[110X returns an isomorphism from [3XS[103X to
        an inverse monoid of partial permutations.[133X
  
  [8XPermutation groups[108X
        [33X[0;6YIf [3XS[103X is a permutation group, then [10XIsomorphismPartialPermMonoid[110X returns
        an  isomorphism from [3XS[103X to an inverse monoid of partial permutations on
        the  set  [10XMovedPoints([3XS[103X[10X)[110X  obtained  using  [2XAsPartialPerm[102X ([14X54.4-1[114X). The
        inverse of this isomorphism is obtained using [2XAsPermutation[102X ([14X42.5-5[114X).[133X
  
  [8XTransformation semigroups[108X
        [33X[0;6YIf   [3XS[103X   is  a  transformation  semigroup  satisfying  [2XIsInverseMonoid[102X
        ([14X51.4-8[114X),  then  [10XIsomorphismPartialPermMonoid[110X  returns  an isomorphism
        from  [3XS[103X  to  an  inverse monoid of partial permutations on a subset of
        [10X[1..DegreeOfTransformationSemigroup([3XS[103X[10X)][110X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XS:=InverseSemigroup( [127X[104X
    [4X[25X>[125X [27XPartialPerm( [ 1, 2, 3, 4, 5 ], [ 4, 2, 3, 1, 5 ] ),[127X[104X
    [4X[25X>[125X [27XPartialPerm( [ 1, 2, 4, 5 ], [ 3, 1, 4, 2 ] ) );;[127X[104X
    [4X[25Xgap>[125X [27XIsMonoid(S); [127X[104X
    [4X[28Xfalse[128X[104X
    [4X[25Xgap>[125X [27Xiso:=IsomorphismPartialPermMonoid(S);[127X[104X
    [4X[28XMappingByFunction( <inverse partial perm semigroup on 5 pts[128X[104X
    [4X[28X with 2 generators>, <inverse partial perm monoid on 5 pts[128X[104X
    [4X[28X with 2 generators>, function( object ) ... end, function( object ) ..\[128X[104X
    [4X[28X. end )[128X[104X
    [4X[25Xgap>[125X [27XSize(S);[127X[104X
    [4X[28X508[128X[104X
    [4X[25Xgap>[125X [27XSize(Range(iso));[127X[104X
    [4X[28X508[128X[104X
    [4X[25Xgap>[125X [27XG:=Group((1,2)(3,8)(4,6)(5,7), (1,3,4,7)(2,5,6,8), (1,4)(2,6)(3,7)(5,8));;[127X[104X
    [4X[25Xgap>[125X [27XIsomorphismPartialPermSemigroup(G);[127X[104X
    [4X[28XMappingByFunction( Group([ (1,2)(3,8)(4,6)(5,7), (1,3,4,7)[128X[104X
    [4X[28X(2,5,6,8), (1,4)(2,6)(3,7)(5,8) ]), <inverse partial perm semigroup [128X[104X
    [4X[28Xon 8 pts[128X[104X
    [4X[28X with 3 generators>, function( p ) ... end, function( f ) ... end )[128X[104X
    [4X[25Xgap>[125X [27XS:=Semigroup(Transformation( [ 2, 5, 1, 7, 3, 7, 7 ] ), [127X[104X
    [4X[25X>[125X [27XTransformation( [ 3, 6, 5, 7, 2, 1, 7 ] ) );;[127X[104X
    [4X[25Xgap>[125X [27Xiso:=IsomorphismPartialPermMonoid(S);;[127X[104X
    [4X[25Xgap>[125X [27XMultiplicativeNeutralElement(S)^iso;[127X[104X
    [4X[28X<identity partial perm on [ 1, 2, 3, 5, 6, 7 ]>[128X[104X
    [4X[25Xgap>[125X [27XOne(Range(iso));[127X[104X
    [4X[28X<identity partial perm on [ 1, 2, 3, 5, 6, 7 ]>[128X[104X
    [4X[25Xgap>[125X [27XMovedPoints(Range(iso));[127X[104X
    [4X[28X[ 1, 2, 3, 5, 6 ][128X[104X
  [4X[32X[104X
  
