Re: [Maxima-discuss] How do I translate the "ev" in "[a:b,b:c,c:d]; ev('[a,b,c],'a=42); " to a "subst"?

[Richard F. <fa...@gm...>]

The code here:

https://people.eecs.berkeley.edu/~fateman/lisp/doparsesum.lisp
provides a more rational version of makelist.  It doesn't hide stuff or
call ev

For instance,



 for i:1 next 2*i while i< 20 collect f(i)


 is translated to
 block([g15:[]],

  for i next 2*i unless i>=20 do  push(f(i),g15),

     reverse(g15))


which returns

	[f(1),f(2),f(4),f(8),f(16)]

I think the code should be added to Maxima.  It is orthogonal to
everything else,

so no existing test suite code could use it . It is unlikely anyone
else in private code hacked

the parser with these keywords..

RJF


On Tue, Oct 15, 2024 at 1:32 AM Robert Dodier <rob...@gm...>
wrote:

> On Mon, Oct 14, 2024 at 12:00 PM Stavros Macrakis <mac...@gm...>
> wrote:
>
> > Internally makelist calls ev, but I've got to say that that shocks me
> even more than the fact that ev has bizarre behavior itself. In particular,
> I find this ridiculous:
> >
> > makelist(['(x), '('x),'('('x))],'x,17,17) => [[17, '17, '('17)]]
> >
> > Re using 'x as a variable in ev and makelist, I doubt that the
> implementers considered that case. It should probably raise an error.
>
> Ah, but this example is easily explained. 'x is a nonatomic expression
> ((MQUOTE) $X) so ev is going to substitute (not assign) ?meval(17) for
> ?meval('x) in ['(x), '('x),'('('x))] and then evaluate that, peeling
> off one quote from each of the three list elements. (I'm pretty
> impressed that it comes out with the right number of quotes on each
> element, frankly.)
>
> I disagree that 'x should cause an error, unless all nonatomic doodads
> cause an error, and I'm inclined to think they shouldn't.
>
> The barely-coherent intricacies of ev spill over into makelist ... Oh
> well!!
>
> Robert
>
>
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