Re: [SPOILER] Re: Perl Quiz of the Week #25 (RPN calculator)

On Oct 6, 2004, at 8:52 AM, Peter Haworth wrote:

> On Tue, 5 Oct 2004 13:01:28 -0400, Mark Jason Dominus wrote:
>> On Oct 5, 2004, at 12:42 PM, Peter Haworth wrote:
>>>
>>> I'm thinking about allowing user-defined functions, but not being
>>> a Forth programmer, I'm not sure how the syntax ought to look.
>>
>> In PostScript you define a procedure by doing something like:
>>
>>       { 2 mul } /double def
>>
>> After processing the '}' operator, the stack contains an anonymous
>> function. '/double' pushes the "name object" representing the name
>> "double", and then "def" is a binary operator which expects a name
>> and a value and associates the two in the current dictionary.
> -- 
> 	Peter Haworth	[email protected]
> "I even make off-by-one errors counting on my fingers.
>  No wonder I can't debug my programs :-)"
> 		-- Nathan Torkington

Just a point of clarification, the postscript would actually be:
   /double { 2 mul } def
or
   { 2 mul } /double exch def

Don't know if this would make for a simpler RPN implementation here
   or not.  But, if anyone were to try this within postscript, they
   would at best get "strange" results, or more probably get a stack
   exception.

mike