add numerical recipes library

lib/nr/k_and_r/recipes/wtn.c

@@ -0,0 +1,38 @@
+
+#include "nrutil.h"
+
+void wtn(a,nn,ndim,isign,wtstep)
+float a[];
+int isign,ndim;
+unsigned long nn[];
+void (*wtstep)();
+{
+	unsigned long i1,i2,i3,k,n,nnew,nprev=1,nt,ntot=1;
+	int idim;
+	float *wksp;
+
+	for (idim=1;idim<=ndim;idim++) ntot *= nn[idim];
+	wksp=vector(1,ntot);
+	for (idim=1;idim<=ndim;idim++) {
+		n=nn[idim];
+		nnew=n*nprev;
+		if (n > 4) {
+			for (i2=0;i2<ntot;i2+=nnew) {
+				for (i1=1;i1<=nprev;i1++) {
+					for (i3=i1+i2,k=1;k<=n;k++,i3+=nprev) wksp[k]=a[i3];
+					if (isign >= 0) {
+						for(nt=n;nt>=4;nt >>= 1)
+							(*wtstep)(wksp,nt,isign);
+					} else {
+						for(nt=4;nt<=n;nt <<= 1)
+							(*wtstep)(wksp,nt,isign);
+					}
+
+					for (i3=i1+i2,k=1;k<=n;k++,i3+=nprev) a[i3]=wksp[k];
+				}
+			}
+		}
+		nprev=nnew;
+	}
+	free_vector(wksp,1,ntot);
+}