Vector in polyratfun vanishes

[jodavies]

In trying to compare OPITeR to other tensor reduction routines I hit the following (due to an autodeclare, I did not notice that q22 was taken as a vector):

#-

Vector q22;
*Symbol q22;

Vector q2;
Symbol D;
CFunction rat;
PolyRatFun rat;

Local test = q2.q2*rat(-1,D - 2);

Identify q2.q2 = rat(q22,1);

Print +s;
.end

produces

test =
    + rat(0,1)
   ;

which then vanishes after another sort.

Putting a scalar product into rat of course crashes like

ERROR: polynomials and polyratfuns must contain symbols only

This goes at least as far back as FORM 4.1, it is a bit surprising that no one encountered this before.

[tueda]

Indeed, v4.0-20120330 and v4.0-20120410 give the same result: + rat(0,1).

[tueda]

Arguments of the ratfun should be checked and the error should occur for these cases:

CF rat;

F f;  * including (C/N)Functions, (C/N)Tensors, (C/N)Tables.
V v;
I i;

PolyRatFun rat;

L F1 = rat(f,1);
L F2 = rat(v,1);
L F3 = rat(i,1);

P;
.end

[jodavies]

The bad test is this one:
https://github.com/vermaseren/form/blob/61ecfdd9655bae0641e6a3a01ae73edfd1a081b9/sources/poly.cc#L2413

Edit: in this case we never actually arrive at that code. The check should be in poly::argument_to_poly. This currently yields a numerator of 0 in the bad cases.

[jodavies]

The problem relates to fast notation. rat(2*f,1) etc already causes termination. The fast notation causes the "non-fast" loop to not run, and simply produces a numerator of 0. The above should fix things I think.