De hexadecimal à decimal

Problème

Programme

unsigned long hex2dec(char *s, unsigned long d) {
  return *s ? hex2dec(s + 1, (d << 4) + *s-'0'-(*s>='A')*7 ) : d;
}

int main (int argc, char **argv) {
  printf("%ld\n", hex2dec(argv[1], 0));
}

Variante

unsigned long hex2dec(char *s, unsigned long d) {
  return *s ? hex2dec(s + 1, (d << 4) + (*s-'0')
  ["\000\001\002\003\004\005\006\007\010\011_______\012\013\014\015\016\017"]): d;
}

int main (int argc, char **argv) {
  printf("%ld\n", hex2dec(argv[1], 0));
}