Re: [Maxima-discuss] verifying simplification in tests, was: sub expression with missing simp flags.

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

The factor() command  implementation's final output is a hack on the 
result of the
internal program that produces a list of factors and multiplicities 
(like the ifactors()  command)

If you do  :lisp (trace pfactor)  you can see that.
If the list of polynomial factors and multiplicities is needed, a small 
hack would suffice.
RJF


On 2/28/21 6:51 AM, Gunter Königsmann wrote:
> The fact that factor() can do three things (factor numbers, factor 
> expressions and try harder to do so within scanmap) often causes 
> confusion between users. I guess it also makes coding more difficult 
> at times...
>
> Am 28. Februar 2021 02:36:48 MEZ schrieb Robert Dodier 
> <rob...@gm...>:
>
>     On Sat, Feb 27, 2021 at 2:43 PM Stavros Macrakis <mac...@al...> wrote:
>
>         The test suite should probably check that all outputs are:
>         Fully flagged with simp flags. Unchanged when resimplified
>         with expand(expr,0,0). 
>
>
>     Okay -- I guess these are things that can be implemented in the code
>     which runs the tests. I forget what the function is called, but it's
>     in src/mload.lisp somewhere.
>
>         Exception: factor(24) can best be tested with
>         string(factor(24)), since args(factor(24)) tests correct with
>         both [2^2,3] and [4,3] -- admittedly, factor(<number>) is a hack. 
>
>
>     Yeah, that's pretty terrible. I wouldn't be too sad if
>     factor(<number>) went away. There is of course ifactors which has a
>     more useful output.
>
>         Exactly as given -- the expected results should not be
>         simplified before comparing, because that misses bugs in
>         simplification. For example, the test a+x accepts both a+x and
>         x+a as correct, even though only x+a is correctly ordered. For
>         some new simplifications I'm working on, I have had to use the
>         string() trick to test them. 
>
>
>     There is some stuff about simplifying MQUOTIENT which has caused
>     heartburn at times -- I think I might have sometimes done something
>     like
>
>     <some input expression>;
>     ''(expected output);
>
>     to ensure the expected output gets the same simplified form as the
>     actual output.
>
>         We also need some tests for output form. This is easy for the
>         1d form using string, harder for 2d form. 
>
>
>     It's not really too much trouble for 2d output -- what I have done
>     many times is to say
>
>     (S: make_string_output_stream (),
>       with_stdout (S, print (my_test_function (x))),
>       get_output_stream_string (S));
>     "a
>     -
>     b";
>
>     or whatever the expected string output is. I guess that's a bit of a
>     hassle, but it's not too bad.
>
>     best,
>
>     Robert Dodier
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