C version because I was bored: int is_valid_email(char *email) { char *at = strstr(email, "@"); if (at <= email || at == strlen(email)

C version because I was bored: int is_valid_email(char *email) { char *at = strstr(email, "@"); if (at <= email || at == strlen(email) + at - 2) return 0; return !isspace(*(at - 1)) && !isspace(*(at + 1)); } Test cases: assert(0 == is_valid_email("")); assert(0 == is_valid_email("@b")); assert(0 == is_valid_email("b@")); assert(0 == is_valid_email("d@ ")); assert(0 == is_valid_email(" @d")); assert(0 == is_valid_email(" ")); assert(1 == is_valid_email("a@b")); assert(1 == is_valid_email("John Smith <x.y@z.com>"));