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#############################################################################
##
#W sparselist.gd GAP library Steve Linton
##
##
#Y Copyright (C) 1996, Lehrstuhl D für Mathematik, RWTH Aachen, Germany
#Y (C) 1998 School Math and Comp. Sci., University of St Andrews, Scotland
#Y Copyright (C) 2002 The GAP Group
##
## This file declares the operations for sparse lists
##
#############################################################################
##
#O SparseStructureOfList( <list> )
##
## This operation returns a sparse structure of <list>
## The return value is a length three list, of which the first
## position may or may not be bound. If bound, it is the default
## value, if not bound, the default is to be unbound. The default value
## must by immutable
##
## The second entry is a dense duplicate-free list of integers
## between 1 and Length(<list>) inclusive, representing the
## positions where non-default entries may appear.
##
## The third entry is a list not longer than the second entry, giving
## the values that appear in the positions given in the second
## entry. Holes in this list represent holes in the original list.
##
## The second and third entries may be mutable (to avoid copying in
## time-critical code) but should not be changed.
##
DeclareOperation( "SparseStructureOfList", [IsList]);
#############################################################################
##
#F IsSparseList( <l> )
##
## A sparse list is a list for which the sparse structure and corresponding
## sparse methods should be used.
##
## The filter is ranked up so that sparse list methods will beat
## competing methods for finite, homogenous, etc. lists, which is
## usually right
##
DeclareFilter( "IsSparseList", IsList );
RANK_FILTERS[FLAG1_FILTER(IsSparseList)] := 20;
#############################################################################
##
#F SparseListBySortedList ( <poss>, <vals>, <len>, <default> )
#F SparseListBySortedListNC( <poss>, <vals>, <len>, <default> )
##
## These two functions can be used to create homogeneous sparse
## lists, in a representation where the positions are stored as a
## sorted list and the values as a corresponding list. These lists
## must be dense.
##
## The NC version refrains from both checking and copying its arguments
## The non-NC version makes a shallow copy of <poss> and <vals>
##
DeclareGlobalFunction( "SparseListBySortedList");
DeclareGlobalFunction( "SparseListBySortedListNC");
#############################################################################
##
#P IsSparseRowVector( <sl> )
##
## A sparse list is a sparse row vector if it is dense and its default value
## is a common Zero of all its non-default values
##
DeclareProperty( "IsSparseRowVector", IsSparseList);
InstallTrueMethod( IsRowVector, IsSparseRowVector );
InstallTrueMethod( IsHomogeneousList, IsSparseRowVector );
InstallTrueMethod( IsCollection, IsSparseRowVector );
#############################################################################
##
#F SparseVectorBySortedList ( <poss>, <vals>, <len>[, <zero>] )
#F SparseVectorBySortedListNC( <poss>, <vals>, <len>[, <zero>])
##
## These two functions can be used to create sparse row vectors using
## the SparseListBySortedList representation, but knowing a priori
## that they are sparse row vectors. The optional <zero> argument is
## needed only when <poss> and <vals> are empty.
##
## The NC version refrains from both checking and copying its arguments
## The non-NC version makes a shallow copy of <poss> and <vals>
##
DeclareGlobalFunction( "SparseVectorBySortedList");
DeclareGlobalFunction( "SparseVectorBySortedListNC");
#############################################################################
##
#E
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