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;
       }

}