Hi all. I'm trying to use ginac for some calculation involving small matrices with symbolic values. I tried the following code: #include <ginac/ginac.h> using namespace GiNaC; main() { matrix M(2,2); matrix N(2,2); matrix H=M*N; } and obtain the error: conversion from `GiNaC::ex' to non-scalar type `GiNaC::matrix' requested I can solve the problem using matrix H=M.mul(N); instead. Anyway I wonder if this is a desired behaviour of the library. I suppose that the object M*N is of type GiNaC::ex because of delayed evaluation of the product. But, in principle, it should be possible, for the library, to understand (at run time, of course) if an object of type ex is a matrix or can be converted to a matrix using evalm(). Thank you for your attention, E. Paolini Dipartimento di Matematica Universita` di Firenze