Summary

 A simple reverse-polish calculator (works with numeric and string operations)

   Accepts numeric and string operands, operations, and function calls.
   Strings that "look like" variables can be used as variables.

   Note: given an overloaded operator/function, this
          always calls the largest (one with the most arguments).
          However, can fool by using 'nil' as arguments to ignore.
          So, for example:
               nil "abcdef" *

          outputs '6'.
   Note: cannot handle functions with more than 3 arguments.
   Note: command line arguments are handled first

This file is part of the (main) package.

Exit()

 Quit the calculator

Pop(stack)

 If stack is empty, write an error message and fail

Write(v)

 Display a value

deref(s)

 Dereference 's'.

dup()

 Duplicate the value on top of the stack

flip()

 Flip top two on stack

gettoken(params)

 generate the tokens in the input stream

help()

 Display a help message

main(params)

popstack()

 Pop off stack top

printable(x)

 Produce printable form of a value.

showmem()

 Display calculator memory

showstack()

 Display calculator stack

tokType(s)

 Identify a token as a value or a variable

tostring()

 Convert a value on the stack to a string

traceoff()

 Turn off tracing

traceon()

 Turn on tracing

var(s)

 return s only if it's a legal variable name...