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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, k;
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] * cos(2 * E_PI * k * n / N);
X[k].i -= x[n] * sin(2 * E_PI * k * n / N);
}
}
}
void idft() {
int n, k;
for(n = 0; n < N; ++n) {
x_out[n] = 0.f;
for(k = 0; k < N; ++k) {
x_out[n] += X[k].r * cos(2 * E_PI * k * n / N) - X[k].i * sin(2 * E_PI * k * n / N);
}
x_out[n] /= 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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