Re: [Maxima-discuss] How do I translate "(map 'list f as)" to Maxima?

[Barton W. <wi...@un...>]

If you have found a bug in map, please report it.   Also, try doing listarith : false and rerunning your examples.

--Barton
________________________________
From: Eduardo Ochs <edu...@gm...>
Sent: Tuesday, October 24, 2023 08:30
To: Michel Talon <ta...@lp...>
Cc: max...@li... <max...@li...>
Subject: Re: [Maxima-discuss] How do I translate "(map 'list f as)" to Maxima?

Non-NU Email
________________________________
Hi Michel,
map sometimes recurses on trees, not on lists:

  f : lambda([x], x+10);
  g : lambda([ab], 10*ab[1]+ab[2]);
  f([3,4]);
  map(f, [[1,2],[3,4],[5,6]]);  /* [[11, 12], [13, 14], [15, 16]] */
  map(g, [[1,2],[3,4],[5,6]]);  /* [12, 34, 56] */
  map(f, [[1,2],[3,4],5]);      /* [[11, 12], [13, 14], 15] */
  map(g, [[1,2],[3,4],5]);      /* error */

It tries to do the right thing and it usually does, but there are some
cases in which its dtrt-iness is not what I expected... so I thought
that it would be nice to also have some functions with a simpler
logic.
  Cheers,
    Eduardo


On Tue, 24 Oct 2023 at 05:48, Michel Talon <ta...@lp...<mailto:ta...@lp...>> wrote:

What is the problem with the simpler:

(%i1) map(lambda([x],x+a),[2,3,4]);
(%o1)                        [a + 2, a + 3, a + 4]
(%i2) x:5;
(%o2)                                  5
(%i3) map(lambda([x],x+a),[2,3,4]);
(%o3)                        [a + 2, a + 3, a + 4]
(%i4) a:3;
(%o4)                                  3
(%i5) map(lambda([x],x+a),[2,3,4]);
(%o5)                              [5, 6, 7]


Le 24/10/2023 à 01:24, Eduardo Ochs a écrit :
Hi list,

what is the right/recommended way to define something like Lisp's
"map" in Maxima? I tried this,

to_lisp();
  (defun foo (x) (* x 10))
  (map 'list 'foo '(2 3 5 8))             ;;-> (20 30 50 80)
  (to-maxima)

map_list(f, as) := makelist(apply(f, [a]), a, as);
map_list(lambda([x], 10*x), [2, 3, 5, 8]);  /* [20, 30, 50, 80]     */
map_list(lambda([x], x+b),  [2, 3, 5, 8]);  /* [b+2, b+3, b+5, b+8] */
map_list(lambda([x], x+a),  [2, 3, 5, 8]);  /* [4, 6, 10, 16]       */

but it doesn't work well in cases like the last one, in which f
mentions a global variable with the same name as the variable used in
the makelist...

Thanks in advance!
  Cheers =),
    Eduardo Ochs




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--
Michel Talon

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