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"fraction" fixes #4462

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"fraction" fixes #4462

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fe3f4ad
minimal fix of #4461
pzinn Jul 1, 2026
7710417
Normalize fractions with unit denominators
pzinn Jul 2, 2026
52ae302
add test for local ring unit denominator normalization
pzinn Jul 19, 2026
8e560c1
Merge branch 'development' of https://github.com/Macaulay2/M2 into frac
pzinn Jul 20, 2026
15bd7b4
add comment about "invert" in code
pzinn Aug 3, 2026
58be3d5
Further frac changes
pzinn Aug 9, 2026
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22 changes: 12 additions & 10 deletions M2/Macaulay2/e/rings/frac.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -111,12 +111,13 @@ void FractionField::simplify(frac_elem *f) const
if (use_gcd_simplify)
{
y = f->denom;
if (R_->is_equal(y, R_->one())) return;
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x = f->numer;
const RingElement *a = RingElement::make_raw(R_, x);
const RingElement *b = RingElement::make_raw(R_, y);
const RingElement *c = rawGCDRingElement(a, b, nullptr, false);
if (!c) return;
if (!R_->is_equal(y, R_->one()))
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{
x = f->numer;
const RingElement *a = RingElement::make_raw(R_, x);
const RingElement *b = RingElement::make_raw(R_, y);
const RingElement *c = rawGCDRingElement(a, b, nullptr, false);
if (!c) return;

#if 0
// Debugging code
Expand All @@ -131,10 +132,11 @@ void FractionField::simplify(frac_elem *f) const
o << newline;
emit(o.str());
#endif
if (!R_->is_equal(c->get_value(), R_->one()))
{
f->numer = R_->divide(f->numer, c->get_value());
f->denom = R_->divide(f->denom, c->get_value());
if (!R_->is_equal(c->get_value(), R_->one()))
{
f->numer = R_->divide(f->numer, c->get_value());
f->denom = R_->divide(f->denom, c->get_value());
}
}
// Now, let's take the content of the denominator, and divide the
// numerator
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7 changes: 7 additions & 0 deletions M2/Macaulay2/tests/normal/matrix-equality.m2
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Expand Up @@ -34,6 +34,13 @@ debug Core
assert isWellDefined f
assert isWellDefined g
assert(f == g) -- fails in version 1.13

-- issue #4461 fix
F = frac(QQ[y])
a = matrix{{1/2}} * matrix{{y}}
b = matrix{{y/2}}
assert(a_(0,0) === b_(0,0))
assert(a == b)
end--

-- Local Variables:
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