#include "cheb.h"

void cheb(float c[MAX], int, float, float);
extern float func(float);
extern double cos(double x);

void cheb(float c[MAX], int n, float xa, float xb)
{
  int k, j;
  float xm, xp, sm;
  float f[MAX];

  xp = (xb + xa) / 2;
  xm = (xb - xa) / 2;

  for(k = 1; k <= n; k++) {
    f[k] = func(xp + xm * (float)cos(PI * (k - 0.5) / n));
  }

  for(j = 0; j <= n-1; j++) {
    sm = 0.0;
    for(k = 1; k <= n; k++) {
      sm = sm + f[k] * (float)cos(PI * (float)j * ((float)k - 0.5) / (float)n);
    }
    c[j] = (float)(2.0 / (float)n) * sm;
  } 
  return;
}