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Fix the README to use the correct version of GAP that's required #876

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merged 5 commits into from
Sep 28, 2022
Merged

Fix the README to use the correct version of GAP that's required #876

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a18a98e
homomorph: fix issue in SemigroupIsoByImages
james-d-mitchell Aug 25, 2022
f3022cb
set `IsInjective` flag before calling `SetNiceMonomorphism` (#870)
ThomasBreuer Sep 17, 2022
733b2d1
libsemigroups/froidure-pin: resolve Issue #869
james-d-mitchell Sep 17, 2022
b468e1c
Merge branch 'stable-5.0'
james-d-mitchell Sep 28, 2022
2287923
README: bump GAP 4.10 -> 4.12
james-d-mitchell Sep 28, 2022
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2 changes: 1 addition & 1 deletion README.md
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Expand Up @@ -22,7 +22,7 @@ For questions, remarks, suggestions, and issues please use the

## Installation

It is assumed that you have a working copy of GAP with version number 4.10.0 or
It is assumed that you have a working copy of GAP with version number 4.12.0 or
higher. The most up-to-date version of GAP and instructions on how to install it
can be obtained from the main [GAP](https://www.gap-system.org) page.

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5 changes: 4 additions & 1 deletion gap/attributes/homomorph.gi
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Expand Up @@ -154,8 +154,11 @@ InstallMethod(SemigroupIsomorphismByImages, "for two semigroup and two lists",
[IsSemigroup, IsSemigroup, IsList, IsList],
function(S, T, gens, imgs)
local hom;
# TODO(Homomorph): we could check for other isomorphism invariants here, like
# we require that gens, and imgs are duplicate free for example, and that S
# and T have the same size etc
hom := SemigroupHomomorphismByImages(S, T, gens, imgs);
if IsBijective(hom) then
if hom <> fail and IsBijective(hom) then
return hom;
fi;
return fail;
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2 changes: 1 addition & 1 deletion gap/libsemigroups/froidure-pin.gi
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Expand Up @@ -724,7 +724,7 @@ function(S)
if IsFpSemigroup(S) or IsFpMonoid(S) or IsQuotientSemigroup(S) then
pos_to_pos_sorted := {T, i} -> i;
product := FroidurePinMemFnRec(S).product_by_reduction;
FroidurePinMemFnRec(S).enumerate(T, N);
FroidurePinMemFnRec(S).enumerate(T, N + 1);
else
pos_to_pos_sorted := FroidurePinMemFnRec(S).position_to_sorted_position;
product := FroidurePinMemFnRec(S).fast_product;
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6 changes: 6 additions & 0 deletions tst/standard/attributes/homomorph.tst
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Expand Up @@ -157,6 +157,12 @@ PartialPerm( [ ], [ ] ) ] ), [ IdentityTransformation ], [ PartialPerm( [ ], [\
] ) ] )
gap> EvalString(String(hom)) = hom;
true
gap> S := TrivialSemigroup();
<trivial transformation group of degree 0 with 1 generator>
gap> T := FullTransformationSemigroup(2);
<full transformation monoid of degree 2>
gap> SemigroupIsomorphismByImages(S, T, [S.1, S.1], [T.1, T.2]);
fail

# homomorph: SemigroupHomomorphismByImages, for infinite semigroup(s)
gap> S := FreeSemigroup(1);;
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20 changes: 20 additions & 0 deletions tst/standard/libsemigroups/froidure-pin.tst
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Expand Up @@ -701,6 +701,26 @@ gap> S := F / R;;
gap> MultiplicationTable(S);
[ [ 1, 2, 3, 4 ], [ 2, 2, 2, 2 ], [ 3, 4, 3, 4 ], [ 4, 4, 4, 4 ] ]

# Issue #869, when the size of an fp semigroup/monoid equals its number of
# generators.
gap> F := FreeSemigroup(6);
<free semigroup on the generators [ s1, s2, s3, s4, s5, s6 ]>
gap> R :=
> [[F.1 ^ 2, F.1], [F.1 * F.2, F.1], [F.1 * F.3, F.1], [F.1 * F.4, F.1],
> [F.1 * F.5, F.5], [F.1 * F.6, F.6], [F.2 * F.1, F.1], [F.2 ^ 2, F.1],
> [F.2 * F.3, F.1], [F.2 * F.4, F.2], [F.2 * F.5, F.5], [F.2 * F.6, F.6],
> [F.3 * F.1, F.3], [F.3 * F.2, F.3], [F.3 ^ 2, F.3], [F.3 * F.4, F.3],
> [F.3 * F.5, F.5], [F.3 * F.6, F.6], [F.4 * F.1, F.1], [F.4 * F.2, F.2],
> [F.4 * F.3, F.3], [F.4 ^ 2, F.4], [F.4 * F.5, F.5], [F.4 * F.6, F.6],
> [F.5 * F.1, F.5], [F.5 * F.2, F.5], [F.5 * F.3, F.5], [F.5 * F.4, F.5],
> [F.5 ^ 2, F.5], [F.5 * F.6, F.5], [F.6 * F.1, F.6], [F.6 * F.2, F.6],
> [F.6 * F.3, F.6], [F.6 * F.4, F.6], [F.6 * F.5, F.6], [F.6 ^ 2, F.6]];;
gap> S := F / R;
<fp semigroup with 6 generators and 36 relations of length 114>
gap> MultiplicationTable(S);
[ [ 1, 1, 1, 1, 5, 6 ], [ 1, 1, 1, 2, 5, 6 ], [ 3, 3, 3, 3, 5, 6 ],
[ 1, 2, 3, 4, 5, 6 ], [ 5, 5, 5, 5, 5, 5 ], [ 6, 6, 6, 6, 6, 6 ] ]

# SEMIGROUPS_UnbindVariables
gap> Unbind(BruteForceInverseCheck);
gap> Unbind(BruteForceIsoCheck);
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