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#include <math.h>
#include <stdio.h>
#define E_PI 3.1415926535897932384626433832795028841971693993751058209749445923078164062
#define N 8
typedef struct {
float r;
float i;
} Complex;
float x[] = {0, 0, 2, 3, 4, 0, 0, 0};
Complex X[N];
float x_out[N];
void dft(int N, Complex *X) {
int i, n, k;
Complex x[N];
for(i = 0; i < N; ++i) {
x[i] = X[i];
}
for(k = 0; k < N; ++k) {
X[k].r = 0.f;
X[k].i = 0.f;
for(n = 0; n < N; ++n) {
X[k].r += x[n].r * cos(2 * E_PI * k * n / N);
X[k].i -= x[n].r * sin(2 * E_PI * k * n / N);
}
}
}
void idft(int N, Complex *X) {
int i, n, k;
Complex x[N];
for(i = 0; i < N; ++i) {
x[i] = X[i];
}
for(n = 0; n < N; ++n) {
X[n].i = 0.f;
X[n].r = 0.f;
for(k = 0; k < N; ++k) {
X[n].r += x[k].r * cos(2 * E_PI * k * n / N) - x[k].i * sin(2 * E_PI * k * n / N);
}
X[n].r /= N;
}
}
int main() {
int k;
dft();
idft();
for(k = 0; k < N; ++k) {
printf("x[%d] = %.2f, X[%d] = %.2f + %.2fi, x_out[%d] = %.2f\n", k, x[k], k, X[k].r, X[k].i, k, x_out[k]);
}
}
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