// quantum computing emulation: addition
//
// q = (a,b) -> (a,(a+b)%N)
//
// q represents qn qubits: a = top n bits, b = bottom m bits, qn = n + m, N = 2**m
//
// Usage: add [qn [n]]
//
// R. Perry, Jan. 2018
//
#include <stdio.h>
#include <stdlib.h> // atoi()
#include <tgmath.h>
#include "qce.h"

// classical add
//
unsigned long f_add( unsigned long a, unsigned long b, unsigned long N)
{
  return (a + b) % N;
}

//---------------------------------------------------------------------

int main( int argc, char *argv[])
{
  unsigned int qn = 2;  if( argc > 1) qn = atoi(argv[1]); // number of qubits in q

  if( qn == 0) error( "add: bad qn arg");

  int n = 0;  if( argc > 2) n = atoi(argv[2]); // number of bits in a

  if( n <= 0) n = qn >> 1;

  unsigned long N = 1LU << (qn - n); // modulus for the addition

  printf( "add: qn = %u, n = %i, N = %lu\n", qn, n, N);

  State q = Q(qn);

 // set q.a[i] = i so we can easily see where the values end up
 //  
  for( unsigned long i = 0; i < q.N; ++i) q.a[i] = i;

  print( "q", q, 1);  operate( q, n, f_add, N);  print( "add", q, 1);

  return 0;
}