Changes since the book version:

1.  The variable "_" contains the result of the last
top-level expression evaluation, so you can re-use
intermediate values without re-typing them.

2.  for statement added, just like the one in C.

3.  ++ and -- added.

4.  Interrupts are caught; use cntrl-D to quit.

5.  % operator added.

6.  +=, -=, etc., added.

7.  \ at end of line eats newline

8.  results are 16 digits

9.  tabs on output are no longer

Jun 1990:

10.	asin, acos, sinh, cosh, tanh, erf, erfc
