#include "puolitus.h"
#include <stdlib.h>
#include <stdio.h>

TYPE puolitus( TYPE(*f)(TYPE), TYPE min, TYPE max)
{
  TYPE mid, val, lastmin, lastmax, fmax;

  if (min>=max) {
    fprintf(stderr, "ERROR: min>=max\n");
    exit(EXIT_FAILURE);
  }
  if ((f(min)>0) == ((fmax=f(max))>0)) {
    fprintf(stderr, "ERROR: f(min) and f(max) have same sign\n");
    exit(EXIT_FAILURE);
  }
  for (;;) {
    mid = (min+max)/2;
    val = f(mid);
#ifdef DEBUG
    printf("min=%.20f, max=%.20f, val(%.20f)=%.20f\n", min, max,mid,val);
#endif
    if (val == 0) 
      return mid;
    lastmin=min; lastmax=max;
    if ((val>0) == (fmax>0)) {
      if (max<=mid) return max;
      max=mid;
    } else {
      if (min>=mid) return min;
      min=mid;
    }
  } 
}