match unequal symbols

[veretin]

Hi!

Suppose I want to do partial fraction of many denominators (below den(x?) means 1/(k.k - x) for example).

s x,y,z, mm1,mm2;
c den,inv;

g ff1 = den(mm1)*den(mm2);
g ff2 = den(mm1)^2;

repeat id den(x?)*den(y?!{,x}) = inv(x-y)*( den(x) - den(y) );

print+s;
.end

Result:

   ff1 =
       + den(mm1)*inv( - mm2 + mm1)
       - den(mm2)*inv( - mm2 + mm1)
      ;

   ff2 = 0;

ff1 is ok. But I dont want to capture terms with x==y.
Construction

id den(x?)*den(y?!{,x}) = inv(x-y)*( den(x) - den(y) );

does not make the job and ignores my check for the set.

[jodavies]

This should work for you, you need the ? in the set:

id den(x?!{y?})*den(y?!{x?}) = inv(x-y)*( den(x) - den(y) );

The restriction is best put on both patterns because you don't "know" which FORM will match first. For eg, this doesn't work:

id den(x?!{y?})*den(y?) = inv(x-y)*( den(x) - den(y) );

but this does:

id den(x?)*den(y?!{x?}) = inv(x-y)*( den(x) - den(y) );

[veretin]

Indeed this works.
Thank you!

[jodavies]

I thought I remembered this being in the manual, but I can't see it there and neither in the tutorial. Let's class this as a "documentation bug" and add something.

[tueda]

I thought I remembered this being in the manual

Maybe this one? Is the example too complicated?
https://github.com/vermaseren/form/blob/638f84b37bd15f9f3beac288d8e7ae97ee0db4f6/doc/manual/variable.tex#L542-L566

[jodavies]

Ah yes, you are right, this covers what is required for this issue. Maybe it could spell out more directly that wildcards may be elements of unnamed sets (with their ?), but the information is indeed there.