Dear Forum members, I am doing some work in GAP with integral group rings, specifically with modules over those. For this, I wanted to get a mutable zero "vector" of a module M (to be modified later on). However, it turns out that ZeroMutable(M) does not work (in GAP 4.4.12) for my case. To my confusion, ZeroMutable(Zero(M)) *does* work. Am I doing something wrong? Is this intentional or a bug?
Here's an explicit example gap> G:=SymmetricGroup(3); # Some group, doesn't matter which Sym( [ 1 .. 3 ] ) gap> ZG:=GroupRing(Integers,G); # integral group ring of G <free left module over Integers, and ring-with-one, with 2 generators> gap> M:=ZG^3; # some ZG module ( <free left module over Integers, and ring-with-one, with 2 generators>^3 ) gap> Zero(M); IsMutable(last); [ <zero> of ..., <zero> of ..., <zero> of ... ] false gap> ZeroMutable(Zero(M)); IsMutable(last); [ <zero> of ..., <zero> of ..., <zero> of ... ] true gap> ZeroMutable(M); Error, no method found! For debugging hints type ?Recovery from NoMethodFound Error, no 1st choice method found for `ZERO_MUT' on 1 arguments called from <function>( <arguments> ) called from read-eval-loop Entering break read-eval-print loop ... you can 'quit;' to quit to outer loop, or you can 'return;' to continue brk> Best regards, Max _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum
