GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
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## LinearAlgebraForCAP package
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## Copyright 2015, Sebastian Gutsche, TU Kaiserslautern
## Sebastian Posur, RWTH Aachen
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#! @Chapter Category of Matrices
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#! @Section Constructors
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#! @Description
#! The argument is a homalg field $F$.
#! The output is the matrix category over $F$.
#! Objects in this category are non-negative integers.
#! Morphisms from a non-negative integer $m$ to a non-negative integer $n$ are given by
#! $m \times n$ matrices.
#! @Returns a category
#! @Arguments F
DeclareAttribute( "MatrixCategory",
IsFieldForHomalg );
DeclareGlobalFunction( "INSTALL_FUNCTIONS_FOR_MATRIX_CATEGORY" );