// re2c $INPUT -o $OUTPUT #include <assert.h> // expect a null-terminated string static int lex(const char *YYCURSOR) { int count = 0; loop: /*!re2c re2c:define:YYCTYPE = char; re2c:yyfill:enable = 0; * { return -1; } [\x00] { return count; } [a-z]+ { ++count; goto loop; } [ ]+ { goto loop; } */ } int main() { assert(lex("") == 0); assert(lex("one two three") == 3); assert(lex("f0ur") == -1); return 0; }