GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
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## HomalgFiltration.gd Modules package Mohamed Barakat
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## Copyright 2007-2010, Mohamed Barakat, University of Kaiserslautern
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## Declaration stuff for a filtration.
##
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#
# global functions and operations:
#
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# basic operations:
DeclareOperation( "HomalgRing",
[ IsHomalgFiltration ] );
DeclareOperation( "MatrixOfFiltration",
[ IsHomalgFiltration, IsInt ] );
DeclareOperation( "MatrixOfFiltration",
[ IsHomalgFiltration ] );
DeclareOperation( "BasisOfModule",
[ IsHomalgFiltration ] );
DeclareOperation( "DecideZero",
[ IsHomalgFiltration ] );
DeclareOperation( "OnLessGenerators",
[ IsHomalgFiltration ] );
DeclareOperation( "ByASmallerPresentation",
[ IsHomalgFiltration ] );