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#############################################################################
##
## This file is part of GAP, a system for computational discrete algebra.
## This file's authors include Steve Linton.
##
## Copyright of GAP belongs to its developers, whose names are too numerous
## to list here. Please refer to the COPYRIGHT file for details.
##
## SPDX-License-Identifier: GPL-2.0-or-later
##
## This file contains the implementations for weak pointer objects
##
#############################################################################
##
#M <wp> [<pos>] access function for weak pointer objects
##
## We cannot use the kernel function directly, as it returns fail for unbound
## see comments in wpobj.gd for the reason.
##
InstallMethod(\[\],
"method for a weak pointer object",
true,
[ IsWeakPointerObject, IsPosInt ],
0,
function( wp, pos)
local elm;
elm := ElmWPObj(wp, pos);
if elm <> fail or IsBoundElmWPObj(wp,pos) then
return elm;
else
Error("<wpobj>[<pos>] must have a value");
fi;
end);
#############################################################################
##
#M <wp> [<pos>] := <obj> weak pointer object member assignment
##
InstallMethod(\[\]\:\=,
"method for a weak pointer object",
true,
[ IsWeakPointerObject and IsMutable, IsPosInt, IsObject ],
0,
SetElmWPObj);
#############################################################################
##
#M Length( <wp> ) note that the answer may not stay valid
##
InstallMethod(Length,
"method for a weak pointer object",
true,
[ IsWeakPointerObject ],
0,
LengthWPObj);
#############################################################################
##
#M IsBound(<wp>[<pos>]) note that the answer may not stay valid
##
InstallMethod(IsBound\[\],
"method for a weak pointer object",
true,
[ IsWeakPointerObject, IsPosInt ],
0,
IsBoundElmWPObj);
#############################################################################
##
#M Unbind(<wp>[<pos>])
##
InstallMethod(Unbind\[\],
"method for a weak pointer object",
true,
[ IsWeakPointerObject and IsMutable, IsPosInt ],
0,
UnbindElmWPObj);
#############################################################################
##
#M Print method, ~ is not supported, so self-referential weak pointer
## objects cannot be printed
##
InstallMethod(PrintObj,
"method for a weak pointer object",
true,
[ IsWeakPointerObject ],
0,
function(wp)
local i,l,x;
Print("WeakPointerObj( [ ");
l := Length(wp);
if l <> 0 then
x := ElmWPObj(wp,1);
if x <> fail or IsBoundElmWPObj(wp,1) then
PrintObj(x);
fi;
for i in [2..l] do
Print(", ");
x := ElmWPObj(wp,i);
if x <> fail or IsBoundElmWPObj(wp,i) then
PrintObj(x);
fi;
od;
fi;
Print(" ] )");
end);
#############################################################################
##
#M View method, ~ is not supported, so self-referential weak pointer
## objects cannot be printed
##
InstallMethod(ViewObj,
"method for a weak pointer object",
true,
[ IsWeakPointerObject ],
0,
function(wp)
local i,l,x;
Print("WeakPointerObj( [ ");
l := Length(wp);
if l <> 0 then
x := ElmWPObj(wp,1);
if x <> fail or IsBoundElmWPObj(wp,1) then
ViewObj(x);
fi;
for i in [2..l] do
Print(", ");
x := ElmWPObj(wp,i);
if x <> fail or IsBoundElmWPObj(wp,i) then
ViewObj(x);
fi;
od;
fi;
Print(" ] )");
end);
#############################################################################
##
#M ShallowCopy(<wp>)
##
## Note that we do not use wp[i] access (see wpobj.gd for explanation)
##
InstallMethod(ShallowCopy,
"method for a weak pointer object",
true,
[ IsWeakPointerObject ],
0,
function(wp)
local w,i,l,x;
w := WeakPointerObj([]);
l := Length(wp);
for i in [1..l] do
x := ElmWPObj(wp,i);
if x <> fail or IsBound(wp[i]) then
w[i] := x;
fi;
od;
return w;
end);
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