/usr/share/gap/pkg/openmath/hasse/hasse.g is in gap-openmath 11.2.0+ds-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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##
#W hasse/hasse.g OpenMath Package Andrew Solomon
#W Marco Costantini
##
#Y Copyright (C) 1999, 2000, 2001, 2006
#Y School Math and Comp. Sci., University of St. Andrews, Scotland
#Y Copyright (C) 2004, 2005, 2006 Marco Costantini
##
## This file contains the function for drawing Hasse diagrams
##
###########################################################################
##
#P IsHasseDiagram
##
## Hasse diagram GAP definitions.
##
DeclareProperty("IsHasseDiagram", IsBinaryRelation);
###########################################################################
## Return the Hasse Diagram of a partial order.
##
HasseDiagram := function(rel)
local h;
h := HasseDiagramBinaryRelation(rel);
SetIsHasseDiagram(h,true);
return h;
end;
# f is a list of elements, le is the comparison function
CreateHasseDiagram := function(f, le)
local rel, lc, tups, i, j, IsMinimalInList, MinElts, EltCovers, ListCovers;
# true iff x is the only element of list which divides x
IsMinimalInList := function(x, list, le)
local i;
for i in list do
if le(i, x) and x <> i then
return false;
fi;
od;
return true;
end;
## return the minimal elements of a list under le
MinElts := function(list, le)
local i;
return Filtered(list, x->IsMinimalInList(x, list, le));
end;
## for x in list, return the elements which cover it under le
EltCovers := function(list, x, le)
local xunder;
xunder := Filtered(list, y->le(x,y) and y <> x);
return MinElts(xunder,le);
end;
## for a list, return the set of pairs, x, covers(x)
ListCovers := function(list,le)
return List(list, x->[x, EltCovers(list, x, le)]);
end;
lc := ListCovers(f, le);
tups := [];
for i in lc do
for j in i[2] do
Append(tups, [DirectProductElement([i[1], j])]);
od;
od;
rel := BinaryRelationByElements(Domain(f), tups);
SetIsHasseDiagram(rel, true);
return rel;
end;
BindGlobal( "OMDirectoryTemporary", DirectoryTemporary() );
BindGlobal("DrawHasse", function(h)
local output, filename;
filename := Filename( OMDirectoryTemporary, "nsinput.html" );
RemoveFile( filename );
output := OutputTextFile( filename, false ); #append
SetPrintFormattingStatus( output, false );
AppendTo(output, TOP_HTML);
OMPutObject(output,h);
AppendTo(output, BOTTOM_HTML);
CloseStream(output);
Exec(Concatenation(BROWSER_COMMAND, " ", filename, " &"));
end);
###########################################################################
#E
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