Sinft.cin

void sinft(float y[], int n) { void realft(float data[], unsigned long n, int isign); int j,n2=n+2; float sum,y1,y2; float theta,wi=0.0,wr=1.0,wpi,wpr,wtemp;// double

theta=M_PI/(float) n;       wtemp=sin((float)0.5*theta); wpr = -2*wtemp*wtemp; wpi=sin(theta); y[1]=0.0; for (j=2;j<=(n>>1)+1;j++) { wr=(wtemp=wr)*wpr-wi*wpi+wr; wi=wi*wpr+wtemp*wpi+wi; y1=wi*(y[j]+y[n2-j]); y2=0.5*(y[j]-y[n2-j]); y[j]=y1+y2; y[n2-j]=y1-y2; }       realft(y,n,1); y[1]*=0.5; sum=y[2]=0.0; for (j=1;j<=n-1;j+=2) { sum += y[j]; y[j]=y[j+1]; y[j+1]=sum; } }