#include "dsp1.h"
#include "dft.h"
#include <iostream>
#include <iomanip>

int main()
{
extern long npt;
extern int inv;
printf("select type of transform\n");
printf("\n");
printf("0 for forward DFT\n");
printf("1 for inverse DFT\n");
scanf_s("%d", &inv);
read_data();
dft();
save_data();
exit(0);
}


void read_data()
{
extern long npt;
int n;
extern complex x[size];

for (n = 0; n< size; ++n)
{
x[n].real = 0;
x[n].imag = 0;
}
if ((in = fopen("coeff.dat", "r")) == NULL)
{
printf("cannot open file coeff.dat\n");
exit(1);
}
fscanf(in, "%ld", &npt);
for (n = 1; n <= npt; n++)
{
fscanf(in, "%lf %lf", &x[n].real, &x[n].imag);
}
fclose(in);
}


void save_data()
{
long k;
int k1;
extern  long npt;
extern complex x[size];
if ((out = fopen("dftout.dat", "w")) == NULL)
{
printf("Cannot open file dftout.dat\n");
exit(1);
}
fprintf(out, "k \t\t XR(k) \t\t XI(k) \n");
fprintf(out, "\n");
for (k = 1; k <= npt; ++k)
{
k1 = k - 1;
fprintf(out, "%d \t %f \t %f \n", k1, x[k].real, x[k].imag);
}
fclose(out);
}

void dft()
{
extern int inv;
extern  long npt;
long k, n;
double WN, wk, c, s, XR[size], XI[size];
extern complex x[size];

WN = 2 * pi / npt;
if (inv == 1)
WN = -WN;
for (k = 0; k<npt; ++k)
{
XR[k] = 0.0;
XI[k] = 0.0;
wk = k*WN;
for (n = 0; n<npt; ++n)
{
c = cos(n*wk);
s = sin(n*wk);
XR[k] = XR[k] + x[n + 1].real*c + x[n + 1].imag*s;
XI[k] = XI[k] - x[n + 1].real*s + x[n + 1].imag*c;
}
if (inv == 1)
{ /* divide by N for IDFT */

XR[k] = XR[k] / npt;
XI[k] = XI[k] / npt;
}
}
for (k = 1; k <= npt; ++k)
{
/* store transformed data in x */

x[k].real = XR[k - 1];
x[k].imag = XI[k - 1];
}

}

이거랑

#pragma once

void dft();
void fft();
void read_data();
void save_data();
int inv;
long npt;
complex x[size];
FILE *in, *out, *fopen();

이 헤드파일이랑

#pragma once
#include <iostream>
#include <iomanip>

#define size 600
#define pi 3.141592654
#define maxbits 30

typedef struct {
double real;
double imag;
double modulus;
double angle;
}complex;

여기까지 입니다!! 주석을 달아야하는데....자꾸 이대로 돌리면 뭐가 안정적이지 않다고 오류가 나서;;