GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
LoadPackage( "Modules" ); ZZ := HomalgRingOfIntegers( ); I := RightSubmodule( "4", ZZ ); ## or I := RightSubmodule( HomalgMatrix( "[ 4 ]", 1, 1, ZZ ) ); J := RightSubmodule( "6", ZZ ); ## or J := RightSubmodule( HomalgMatrix( "[ 6 ]", 1, 1, ZZ ) ); IpJ := I + J; IJ := I * J; IiJ := Intersect( I, J );