Groups > comp.lang.postscript > #2083

Re: map and higher order functions

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From	Carlos <angus@quovadis.com.ar>
Newsgroups	comp.lang.postscript
Subject	Re: map and higher order functions
Date	Thu, 30 Oct 2014 19:55:24 +0100
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[ken <ken@spamcop.net>, 2014-10-30 16:57]
> In article <20141030172728.0983c6bc@samara.DOMA>,
> angus@quovadis.com.ar says...
> > 
> > How would you implement map and other higher order functions
> > (procedures taking one or more procedures)?
> 
> I'm not sure what your 'map' function is intended to do, but...

This is what it's intended to do:

GS>[ 1 2 3 4 ] { 1 add } map ==
[2 3 4 5]

Inside map, I have to exec the proc ({ 1 add } in this case) without
having anything on the stack. Otherwise, this

GS> 3 [ 1 2 3 4 ] { 1 index add } map ==
[4 5 6 7]

wouldn't work, since "1 index" would retrieve some value used
internally by map, and not what the user expects.

I can't also simply use an entry in userdict, because it would get
clobbered if the function re-enters, and this would fail:

GS>[ [ 1 2 3 ] [ 4 5 6 ] ] { { 1 add } map } map ==
[[2 3 4] [5 6 7]]

Nor can I have anything on the dictionary stack (using "n dict
begin ... end" to hold "local variables"), because the user might
execute a "def" inside the procedure, and the entry would be stored in
the wrong dictionary.

I'd like to know what the options are to solve this problem.

I hope it is clearer now.

> [...]

--

Thread

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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