add numerical recipes library

lib/nr/ansi/examples/xchebpc.c

@@ -0,0 +1,42 @@
+
+/* Driver for routine chebpc */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+
+#define NVAL 40
+#define PIO2 1.5707963
+
+float func(float x)
+{
+	return x*x*(x*x-2.0)*sin(x);
+}
+
+int main(void)
+{
+	int i,j,mval;
+	float a=(-PIO2),b=PIO2,poly,x,y;
+	float c[NVAL],d[NVAL];
+
+	chebft(a,b,c,NVAL,func);
+	for (;;) {
+		printf("\nHow many terms in Chebyshev evaluation?\n");
+		printf("Enter n between 6 and %2d. (n=0 to end).\n",NVAL);
+		scanf("%d",&mval);
+		if ((mval <= 0) || (mval > NVAL)) break;
+		chebpc(c,d,mval);
+		/* Test polynomial */
+		printf("\n%9s %14s %14s\n","x","actual","polynomial");
+		for (i = -8;i<=8;i++) {
+			x=i*PIO2/10.0;
+			y=(x-0.5*(b+a))/(0.5*(b-a));
+			poly=d[mval-1];
+			for (j=mval-2;j>=0;j--) poly=poly*y+d[j];
+			printf("%12.6f %12.6f %12.6f\n",x,func(x),poly);
+		}
+	}
+	return 0;
+}
+#undef NRANSI