Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix DisplaySemigroup for transformation semigroups #1785

Merged
merged 1 commit into from
Oct 27, 2017
+59 −20
Merged

Fix DisplaySemigroup for transformation semigroups #1785

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions doc/ref/semigrp.xml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -206,6 +206,7 @@ The following functions deal with quotient semigroups in ⪆.
<#Include Label="GroupHClassOfGreensDClass">
<#Include Label="IsGroupHClass">
<#Include Label="IsRegularDClass">
<#Include Label="DisplaySemigroup">

</Section>

Expand Down
20 changes: 11 additions & 9 deletions lib/semigrp.gd
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -537,24 +537,26 @@ DeclareProperty("IsInverseSemigroup", IsSemigroup);
##
#O DisplaySemigroup( <S> )
##
## <#GAPDoc Label="DisplaySemigroup">
## <ManSection>
## <Oper Name="DisplaySemigroup" Arg='S'/>
##
## <Description>
## Produces a convenient display of a semigroup's DClass
## structure. Let <A>S</A> have degree <M>n</M>. Then for each <M>r\leq n</M>, we
## show all D classes of rank <M>n</M>.
## Produces a convenient display of a transformation semigroup's D-Class
## structure. Let <A>S</A> be a transformation semigroup of degree
## <M>n</M>. Then for each <M>r\leq n</M>, we show all D-classes of
## rank <M>r</M>.
## <P/>
## A regular D class with a single H class of size 120 appears as
## <Example><![CDATA[
## *[H size = 120, 1 L classes, 1 R classes]
## ]]></Example>
## A regular D-class with a single H-class of size 120 appears as
## <Log><![CDATA[
## *[H size = 120, 1 L-class, 1 R-class]
## ]]></Log>
## (the <C>*</C> denoting regularity).
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareOperation("DisplaySemigroup",
[IsSemigroup]);
DeclareOperation("DisplaySemigroup", [IsSemigroup]);

# Everything from here...

Expand Down
40 changes: 29 additions & 11 deletions lib/semigrp.gi
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -422,20 +422,29 @@ InstallMethod(DisplaySemigroup, "for finite semigroups",
[IsTransformationSemigroup],
function(S)

local dc, i, len, sh, D, layer, displayDClass;
local dc, i, len, sh, D, layer, displayDClass, n;

displayDClass:= function(D)
local h, sh;
local h, nrL, nrR;
h:= GreensHClassOfElement(AssociatedSemigroup(D),Representative(D));
if IsRegularDClass(D) then
Print("*");
else
Print(" ");
fi;
nrL := Size(GreensRClassOfElement(AssociatedSemigroup(D),
Representative(h))) / Size(h);
nrR := Size(GreensLClassOfElement(AssociatedSemigroup(D),
Representative(h))) / Size(h);
Print("[H size = ", Size(h), ", ", nrL, " L-class");
if nrL > 1 then
Print("es");
fi;
Print(", ", nrR, " R-class");
if nrR > 1 then
Print("es");
fi;
Print("[H size = ", Size(h),", ",
Size(GreensRClassOfElement(AssociatedSemigroup(D),
Representative(h)))/Size(h), " L classes, ",
Size(GreensLClassOfElement(AssociatedSemigroup(D),
Representative(h)))/Size(h)," R classes]");
Print("\n");
Print("]\n");
end;

#########################################################################
Expand All @@ -446,13 +455,22 @@ function(S)

# check finiteness
if not IsFinite(S) then
TryNextMethod();
TryNextMethod();
fi;

# determine D classes and sort according to rank.
layer:= List([1..DegreeOfTransformationSemigroup(S)], x->[]);
n := DegreeOfTransformationSemigroup(S);

if n = 0 then
# special case for the full transformation monoid on one point
Print("Rank 0: ");
displayDClass(GreensDClasses(S)[1]);
return;
fi;

layer:= List([1 .. n], x->[]);
for D in GreensDClasses(S) do
Add(layer[RankOfTransformation(Representative(D))], D);
Add(layer[RankOfTransformation(Representative(D), n)], D);
od;

# loop over the layers.
Expand Down
18 changes: 18 additions & 0 deletions tst/testinstall/semigrp.tst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -481,6 +481,24 @@ s3*s1
gap> Random(GlobalRandomSource, S);
s3*s2^2

#T# Test DisplaySemigroup
gap> DisplaySemigroup(FullTransformationSemigroup(1));
Rank 0: *[H size = 1, 1 L-class, 1 R-class]
gap> DisplaySemigroup(FullTransformationSemigroup(2));
Rank 2: *[H size = 2, 1 L-class, 1 R-class]
Rank 1: *[H size = 1, 2 L-classes, 1 R-class]
gap> DisplaySemigroup(FullTransformationSemigroup(3));
Rank 3: *[H size = 6, 1 L-class, 1 R-class]
Rank 2: *[H size = 2, 3 L-classes, 3 R-classes]
Rank 1: *[H size = 1, 3 L-classes, 1 R-class]
gap> S := Semigroup([
> Transformation([1, 1, 1, 2]),
> Transformation([1, 1, 2, 1])]);;
gap> DisplaySemigroup(S);
Rank 2: [H size = 1, 1 L-class, 1 R-class]
Rank 2: [H size = 1, 1 L-class, 1 R-class]
Rank 1: *[H size = 1, 1 L-class, 1 R-class]

#
gap> STOP_TEST( "semigrp.tst", 1);

Expand Down