D.7.4.2 torus

Usage:

torus(<int>)

Returns:

torus(n) sets the current group to an n-dimensional torus. The following global variables will be changed:
group of type <ring>
groupideal of type <ideal>
reynolds of type <proc>
The quotient of of `group` and `groupideal` is the coordinate ring of an n-dimensional torus. The basering will be set to 'group'.

LIB "invar.lib";
torus(3);
Invar::group;
==> // coefficients: QQ
==> // number of vars : 4
==> //        block   1 : ordering dp
==> //                  : names    g(1) g(2) g(3) g(4)
==> //        block   2 : ordering C
groupideal;
==> groupideal[1]=g(1)*g(2)*g(3)*g(4)-1