add numerical recipes library

lib/nr/k_and_r/recipes/quadvl.c

@@ -0,0 +1,17 @@
+
+#include "nrutil.h"
+
+void quadvl(x,y,fa,fb,fc,fd)
+float *fa,*fb,*fc,*fd,x,y;
+{
+	float qa,qb,qc,qd;
+
+	qa=FMIN(2.0,FMAX(0.0,1.0-x));
+	qb=FMIN(2.0,FMAX(0.0,1.0-y));
+	qc=FMIN(2.0,FMAX(0.0,x+1.0));
+	qd=FMIN(2.0,FMAX(0.0,y+1.0));
+	*fa=0.25*qa*qb;
+	*fb=0.25*qb*qc;
+	*fc=0.25*qc*qd;
+	*fd=0.25*qd*qa;
+}