Comparison operator using adders and logic

adder_based_comparison.c

//comparison operator using adders
//(C) 2023 Victor Suarez Rovere

#include <stdio.h>


//select type (all were tested)
typedef unsigned char type;
//typedef signed char type;
//typedef unsigned short type;
//typedef signed short type;

int has_carry(size_t a)
{
  return a & (1<<(sizeof(type)*8));
}

int comp1(type a, type b)
{
  return a > b;
}

int comp2(type a, type b)
{
  return !has_carry(a + ~b);
}

int main()
{
  size_t count = 0;
  type a = 0, b  = 0;
  for(;;)
  {
    for(;;)
    {
      int r1 = comp1(a, b);
      int r2 = comp2(a, b);
      if(r1 != r2)
      {
        printf("TEST NOT PASSED: a=%d, b=%d, first result=%d, second result=%d\n", a, b, r1, r2);
        return 1;
      }
      ++count;

      if(++b == 0)
        break;
    }
    if(++a == 0)
      break;
  }
  
  printf("TESTS PASSED, count=%ld\n", count);
  return 0;
}