GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
#############################################################################
##
#W addcoset.gd GAP library Thomas Breuer
##
##
#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 additive cosets.
##
#############################################################################
##
#C IsAdditiveCoset( <D> )
##
## An additive coset is an external additive set whose additively acting
## domain is an additive group.
## The additive coset and its additively acting domain lie in the same
## family.
##
## Note that additive cosets for non-commutative addition are not supported.
##
DeclareCategory( "IsAdditiveCoset",
IsExtASet and IsAssociativeAOpESum and IsTrivialAOpEZero );
#############################################################################
##
#O AdditiveCoset( <A>, <a> )
##
DeclareOperation( "AdditiveCoset", [ IsAdditiveGroup, IsAdditiveElement ] );
#############################################################################
##
#E