InnerProduct(x, y)
Here  x and y  are some modules of  the  Hecke algebra (ie. Specht
modules, PIMS, or  simple modules).  InnerProduct(x, y) computes
the standard inner product of   these  elements. This is sometimes   a
convenient way to compute decomposition numbers (for example).
gap> InnerProduct(H.S(2,2,2,1), H.P(4,3)); 1 gap> DecompositionNumber(H,[2,2,2,1],[4,3]); 1
This function requires the package ``specht'' (see RequirePackage).
GAP 3.4.4