isnum tests if a string represents a number res = isnum(str) str a character string or a matrix of character strings. res a boolean matrix. res = isnum(str) returns %t if str represents a number. isnum does not handle "operations", but only pure scalar numbers. For instance, isnum("1+2*3") will return %f. Complex numbers are not concerned, because one complex number is defined by the addition of two parts. isletter isdigit isalphanum evstr