Macro versions of pinMode and digitalWrite. Tend to be faster and smaller.

econ_101.h

/**
 * This file will reduce the size of and improve the performance of certain arduino code
 * 1. It strips away about 310 bytes of overhead by replacing the implicit main function with a minimal one (which will also be faster)
 * 2. It replaces the library `pinMode` and `digitalWrite` code with register-based variants - saving 120 
 *    bytes - and which which perform faster than the built-ins for single-pin changes (for multi-pin changes,
 *    use the registers yourself).
 */
#ifndef ECON_101
#define ECON_101

#define BITMASK(n) (1 << ((n) & 7))

#define DDR(n) ((n) < 8 ? DDRD : ((n) < 14 ? DDRB : DDRC))
#define DDR_ON(n) DDR(n) |= BITMASK(n)
#define DDR_OFF(n) DDR(n) &= ~BITMASK(n)
#define pinMode(n, s) (s) == OUTPUT ? DDR_ON(n) : DDR_OFF(n); (s) == INPUT_PULLUP && (PORT_ON(n))

#define PORT(n) ((n) < 8 ? PORTD : ((n) < 14 ? PORTB : PORTC))
#define PORT_ON(n) PORT(n) |= BITMASK(n)
#define PORT_OFF(n) PORT(n) &= ~BITMASK(n)
#define digitalWrite(n, s) ((s) ? PORT_ON(n) : PORT_OFF(n))

int main() {
  setup();
  while (true) loop();
}

#endif