Math functions in expr can be coded in Tcl
==========================================

  Rev 0.11: No longer need to specify arg count
  Rev 0.10: Initial release


This is an adaption of the "intfun" and "doublefun" extension, written
by Donal K. Fellows to define arbitrary math functions for use in expr:
    http://www.cs.man.ac.uk/~fellows/tcl/funcproc.c

This code uses a single "mathf" command, with the return type specified
as one of the arguments, and it allows passing a "curried" proc.  But
most importantly, this now uses the Tcl_Obj* API which is much faster.

Here is an example:

    proc multiple {a b} {
      return [expr {$a * $b}]
    }

    mathf inch2cm double multiple 2.54

    puts "1 foot = [expr {inch2cm(12)}] cm"

There is one catch: the call to custom math functions cannot be used at
global level, because the bytecode compiler will compile expr before
the mathf command has actually created the function definition.  But if
placed inside a proc, everything should be fine.