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##
## Datastructures: GAP package providing common datastructures.
##
## Copyright (C) 2015-2019 The datastructures team.
## For list of the team members, please refer to the COPYRIGHT file.
##
## This package is licensed under the GPL 2 or later, please refer
## to the COPYRIGHT.md and LICENSE files for details.
##
##
## This file defines slices.
##
#! @Chapter Slices
#! @Section API
InstallGlobalFunction(Slice,
function(list, begin, len)
local o;
# begin - 1 because GAP lists are 1 indexed
if IsSliceRep( list ) then
# Avoid recursive constructions of slices.
o:= Objectify( SliceTypeMutable,
rec( list:= list!.list,
begin:= begin + list!.begin - 1,
len:= len ) );
else
o := Objectify(SliceTypeMutable, rec(list := list, begin := begin - 1, len := len));
fi;
if IsSmallList(list) then
SetIsSmallList(o, true);
fi;
return o;
end);
InstallMethod(ViewString, "for slices",
[ IsSliceRep ], SUM_FLAGS,
function(slice)
return STRINGIFY("<slice size=", slice!.len, ">");
end);
InstallMethod(ViewObj, "for slices",
[ IsSliceRep ], SUM_FLAGS,
function(slice)
Print("<slice size=", slice!.len, ">");
end);
#! @Description
#! List-style access for slices.
#! @Arguments slice, value
InstallMethod(\[\],
"for a slice and a positive integer",
[ IsSliceRep, IsPosInt ],
function(slice, o)
if o < 1 or o > slice!.len then
ErrorNoReturn("Cannot access element ", o, " of a range with ",
slice!.len, " elements");
fi;
return slice!.list[o + slice!.begin];
end);
#! @Description
#! List-style assignment for slices.
#! @Arguments slice, value, object
InstallMethod(\[\]\:\=,
"for a slice, a key and a value",
[ IsSliceRep and IsMutable, IsPosInt, IsObject ],
function(slice, o, x)
if o < 1 or o > slice!.len then
ErrorNoReturn("Cannot access element ", o, " of a range with ",
slice!.len, " elements");
fi;
slice!.list[o + slice!.begin] := x;
end);
#! @Description
#! Test whether a value is stored in the slice.
#! @Arguments object, slice
InstallMethod( \in,
"for a slice and a key",
[ IsObject, IsSliceRep ],
function(o, slice)
local i;
for i in [slice!.begin..slice!.begin + slice!.len - 1] do
if IsBound(slice!.list[i]) and slice!.list[i] = o then
return true;
fi;
od;
return false;
end);
#! @Description
#! Test whether a location is bound in a slice.
#! @Arguments slice, value
InstallMethod( IsBound\[\],
"for a slice and a key",
[ IsSliceRep, IsPosInt ],
function(slice, o)
if o < 1 or o > slice!.len then
return false;
fi;
return IsBound(slice!.list[slice!.begin + o]);
end);
#! @Description
#! Unbind a value from a slice.
#! @Arguments slice, value
InstallMethod( Unbind\[\],
"for a slice and a positive integer",
[ IsSliceRep and IsMutable, IsPosInt ],
function(slice, o)
if o >= 1 and o <= slice!.len then
Unbind(slice!.list[slice!.begin + o]);
fi;
end);
#! @Description
#! Determine the length of a slice.
#! @Arguments slice
InstallMethod( Length,
"for a slice",
[ IsSliceRep ],
slice -> slice!.len);
[ Dauer der Verarbeitung: 0.3 Sekunden
(vorverarbeitet)
]
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