// plot sign of f(x,y) = x**y - y**x in color
//
// R: f > 0, G: f == 0, B: f < 0
//
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
 
#include "ppm.h"
 
// return indication of the sign of f, avoiding overflow
//
// f(x,y) = exp(log(x)*y) - exp(log(y)*x)
//
double f( double x, double y)
{
  if( x == 0 && y == 0)
    return 0;
  else
    return log(x)*y - log(y)*x;
}

int main( int argc, char *argv[])
{
  int n = 250;
  if( argc > 1) n = atoi( argv[1]);
  ppm a = ppm_new( n, n);
 
  double z;

  for( int i = 0; i < n; ++i)
    for( int j = 0; j < n; ++j)
    {
      a.r[i][j] = a.g[i][j] = a.b[i][j] = 0;

      z = f(j,i);

      if( z > 0) a.r[i][j] = 255;
      else if( z == 0) a.g[i][j] = 255;
      else a.b[i][j] = 255;
    }

  ppm_write( a);
 
  return 0;
}