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Re: map and higher order functions

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[luser- -droog <mijoryx@yahoo.com>, 2014-10-30 22:56]
> On Thursday, October 30, 2014 11:27:49 AM UTC-5, Carlos wrote:
> > How would you implement map and other higher order functions
> > (procedures taking one or more procedures)?
> > 
> > Especially the part when the procedure is to be run, and you must
> > clear the stacks from your working elements.
> > [...]
> 
> I've run into similar issues trying to write procedures that work 
> like "control structures", like loops. The trick I've found is to 
> use the `token` operator to dynamically build a new procedure body
> based on a string template.
> [...]
> I used this trick to make a loop body that calls a user proc.
> But it leaves the dictstack clean while the user proc is 
> executing, and then reclaims the dictionary. Like this,
> 
>   1 dict begin
>   /DICT currentdict def
>   /x 1 def
>   ({ //x add //DICT begin /x 2 def end }) token pop exch pop
>   end
> [...]

This is great! It makes everything so much simpler. That's exactly what
I was looking for. Thanks.

Carlos.

PS: the new implementation:

% <array/string> <proc> map <new array/string>
/map {
    4 dict begin
        /proc exch def
        /arr exch def
        /res arr length
             arr type /stringtype eq { string } { array } ifelse
        def
        /i 1 array def
        ({
            0 1 //arr length 1 sub { % for
                dup //i 0  3 -1 roll  put
                //arr exch get
                //proc exec
                //res //i 0 get  3 -1 roll  put
            } for
            //res
        }) token pop exch pop bind
    end
    exec
} bind def

-- 

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map and higher order functions Carlos <angus@quovadis.com.ar> - 2014-10-30 17:27 +0100
  Re: map and higher order functions ken <ken@spamcop.net> - 2014-10-30 16:57 +0000
    Re: map and higher order functions Carlos <angus@quovadis.com.ar> - 2014-10-30 19:55 +0100
      Re: map and higher order functions ken <ken@spamcop.net> - 2014-10-31 12:17 +0000
  Re: map and higher order functions Ross Presser <rpresser@gmail.com> - 2014-10-30 20:30 -0700
    Re: map and higher order functions Carlos <angus@quovadis.com.ar> - 2014-11-01 23:58 +0100
  Re: map and higher order functions luser- -droog <mijoryx@yahoo.com> - 2014-10-30 22:56 -0700
    Re: map and higher order functions Carlos <angus@quovadis.com.ar> - 2014-11-02 00:15 +0100
      Re: map and higher order functions luser- -droog <mijoryx@yahoo.com> - 2014-11-15 00:43 -0800
        Re: map and higher order functions Carlos <angus@quovadis.com.ar> - 2014-11-16 01:37 +0100
          Re: map and higher order functions luser- -droog <mijoryx@yahoo.com> - 2014-11-21 00:17 -0800
          Re: map and higher order functions luser- -droog <mijoryx@yahoo.com> - 2015-02-27 00:59 -0800

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