1. A method for determining the equivalence of two algebraic functions, the method including the steps of:— (a) determining the symbol sets of the two functions; (b) forming a matrix having a row for each symbol of one function and a column for each symbol of the other function; (c) subjecting the functions to predetermined tests and incrementing the entries in the matrix in accordance with the results of said tests; and (d) testing the matrix against predetermined rules for the symmetry of the matrix.