Re: [Maxima-discuss] Crude first attempt at a Maxima 'assert()' macro

[Stavros M. <mac...@gm...>]

Looks about right. But you don't need eargs:ev(args) -- that will end up
evaluating the argument twice, as you can see here:

assert(2>1,print(oops)) => prints oops


Also, I'd use *is(...) *instead of *ev(...,pred)*, because *ev* is a weird
DWIM <https://en.wikipedia.org/wiki/DWIM>-type command designed for
interactive use which does surprising things sometimes.

          -s

PS An example of an *ev* surprise:

assume(neg<0,pos>0)$
neg:'pos$
is('neg<'pos) => true
ev('neg<'pos,pred) => false
test:'(neg<pos)
ev(test,pred) => false
is(test) => true


On Tue, Jan 30, 2024 at 4:28 PM Henry Baker <hb...@pi...> wrote:

> I've written plenty of macros in Lisp, but this is my first
>
> attempt at a Maxima macro, so don't laugh!
>
>
>
> assert(<boolean expression>, <stuff to print>...)
>
>
>
> Evaluate <boolean expression> and call error if the boolean
>
> expression evaluates to 'false'.
>
>
>
> The rest of the args are passed along to 'error' when it is
>
> called.
>
>
>
> I'm not comfortable enough with Maxima macros or 'buildq' to
>
> know if I'm using the local variables correctly.
>
>
>
> Any improvements to suggest ?
>
>
>
> maxima -b assert.mac
>
> Maxima 5.45.1 https://maxima.sourceforge.io
> using Lisp GNU Common Lisp (GCL) GCL 2.6.12
> Distributed under the GNU Public License. See the file COPYING.
> Dedicated to the memory of William Schelter.
> The function bug_report() provides bug reporting information.
> (%i1) batch("assert.mac")
>
> read and interpret /home/foobar/assert.mac
> (%i2) assert(be,[args])::=buildq([sbe:string(be),ebe:ev(be,pred),
>                                   eargs:ev(args)],
>              if not ebe
>                  then apply('error,append(["assert",sbe,"failed"],eargs))
>                  else true)
> (%o2) assert(be, [args]) ::= buildq([sbe : string(be), ebe : ev(be, pred),
> eargs : ev(args)], if not ebe then apply('error,
> append(["assert", sbe, "failed"], eargs)) else true)
> (%i3) foo:3
> (%o3)                                  3
> (%i4) assert(foo > 2,"foo =",foo)
> (%o4)                                true
> (%i5) assert(foo > 3,"foo =",foo)
> assert foo > 3 failed foo = 3
>  -- an error. To debug this try: debugmode(true);
> (%o6)                       /home/foobar/assert.mac
>
>
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