#include <stdio.h>
#include <math.h>
#include <memory.h>

#define FACTOR 0.85

typedef float(*FuncType1)(float*, int, float);

/*********************************
parameters:
c - pointer to array of coeficients
n - polynom order
x - point of evaluation

returned value:
polynom evaluation at x
*********************************/
float Polynom(float *c, int n, float x);


/*********************************
parameters:
f1,f2 - pointers to two user defined functions
c,n   - polynom coefficients and order
x0,x1 - lower and upper evalation range
dx    - evaluation interval
y     - pointer to array of function evaluations

returned value:
none
*********************************/
void MyFunction(FuncType1 f1, float *c, int n, float x0, float x1, float dx, float *y);

int main()
{
  FILE *fp_in,*fp_out;
  int i,nc,ny;
  float *pc,*py,dx,x0,x1,x;

  // initializing variables
  dx    = 0.1;
  x0    = 0.0;
  x1    = 10.0;
  ny    = (int)(x1-x0)/dx+1;
  py    = malloc(ny*sizeof(float));
  memset(py,0,ny*sizeof(float));

  // loading data from input file
  fp_in = fopen("/home/ohadbara/Programming/demo/Input.dat","rb");
  fscanf(fp_in,"%d",&nc);	
  pc = malloc(nc*sizeof(float));
  for(i=0; i<nc; i++)
    fscanf(fp_in,"%f",&pc[i]);
  fclose(fp_in);

  // calling to user defined function
  MyFunction(Polynom,pc,nc,x0,x1,dx,py);

  // saving results to output file
  fp_out  = fopen("/home/ohadbara/Programming/demo/Output.dat","wb");
  for(x=x0,i=0; x<=x1; x+=dx,i++)
    fprintf(fp_out,"%f %f\n", x, py[i]);
  fclose(fp_out);

  free (py);
  free (pc);

  return 0;
}

float Polynom(float *c, int n, float x)
{
  int i;
  float p;

  p=0;
  for(i=0;i<n;i++)
    p=p+c[i]*pow(x,i);

  return p;
}

void MyFunction(FuncType1 f1, float *c, int n, float x0, float x1, float dx, float *y)
{
  int i;
  float x,xc;

  xc=0.5*(x0+x1);
  for(x=x0,i=0;x<=x1;x+=dx,i++)
  {
    if(x<=xc)
      y[i]=FACTOR*f1(c,n,x);
    else
      y[i]=0.;
  }
}