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#############################################################################
##
## digraphs.g
## Copyright (C) 2014-19 James D. Mitchell
##
## Licensing information can be found in the README file of this package.
##
#############################################################################
##
DeclareOperation("DeclareAttributeThatReturnsDigraph", [IsString, IsOperation]);
DeclareOperation("InstallMethodThatReturnsDigraph",
[IsOperation, IsString, IsList, IsFunction]);
InstallMethod(DeclareAttributeThatReturnsDigraph, "for a string",
[IsString, IsOperation],
function(oper_name, filt)
local attr_name, has_attr_name, oper, attr, has_attr;
attr_name := Concatenation(oper_name, "Attr");
has_attr_name := Concatenation("Has", attr_name);
DeclareOperation(oper_name, [filt]);
DeclareAttribute(attr_name, filt);
oper := ValueGlobal(oper_name);
attr := ValueGlobal(attr_name);
has_attr := ValueGlobal(has_attr_name);
InstallMethod(oper, Concatenation("for a digraph with ", has_attr_name),
[IsDigraph and has_attr], SUM_FLAGS, attr);
InstallMethod(attr, "for an immutable digraph", [IsImmutableDigraph], oper);
# Now it suffices to install a method for the oper and a subcategory of
# filt and this ought to just work.
end);
InstallMethod(InstallMethodThatReturnsDigraph,
"for an operation, info string, list of argument filters, and function",
[IsOperation, IsString, IsList, IsFunction],
function(oper, info, filt, func)
InstallMethod(oper, info, filt,
function(D)
local C, attr_name, set_attr;
C := func(D);
if IsImmutableDigraph(D) then
if not IsImmutableDigraph(C) then
MakeImmutable(C);
fi;
attr_name := Concatenation(NameFunction(oper), "Attr");
set_attr := ValueGlobal(Concatenation("Set", attr_name));
set_attr(D, C);
fi;
return C;
end);
end);
[ Dauer der Verarbeitung: 0.8 Sekunden
(vorverarbeitet)
]
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