add numerical recipes library

lib/nr/ansi/examples/xplgndr.c

@@ -0,0 +1,45 @@
+
+/* Driver for routine plgndr */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define MAXSTR 80
+
+int main(void)
+{
+	char txt[MAXSTR];
+	int i,j,m,n,nval;
+	float fac,val,x;
+	FILE *fp;
+
+	if ((fp = fopen("fncval.dat","r")) == NULL)
+		nrerror("Data file fncval.dat not found\n");
+	fgets(txt,MAXSTR,fp);
+	while (strncmp(txt,"Legendre Polynomials",20)) {
+		fgets(txt,MAXSTR,fp);
+		if (feof(fp)) nrerror("Data not found in fncval.dat\n");
+	}
+	fscanf(fp,"%d %*s",&nval);
+	printf("\n%s\n",txt);
+	printf("%4s %4s %10s %17s %24s\n","n",
+		"m","x","actual","plgndr(n,m,x)");
+	for (i=1;i<=nval;i++) {
+		fscanf(fp,"%d %d %f %f",&n,&m,&x,&val);
+		fac=1.0;
+		if (m > 0)
+			for (j=n-m+1;j<=n+m;j++) fac *= j;
+		fac *= 2.0/(2.0*n+1.0);
+		val *= sqrt(fac);
+		printf("%4d %4d %13.6f %19.6e %19.6e\n",
+			n,m,x,val,plgndr(n,m,x));
+	}
+	fclose(fp);
+	return 0;
+}
+#undef NRANSI