add numerical recipes library

lib/nr/k_and_r/recipes/fleg.c

@@ -0,0 +1,21 @@
+
+void fleg(x,pl,nl)
+float pl[],x;
+int nl;
+{
+	int j;
+	float twox,f2,f1,d;
+
+	pl[1]=1.0;
+	pl[2]=x;
+	if (nl > 2) {
+		twox=2.0*x;
+		f2=x;
+		d=1.0;
+		for (j=3;j<=nl;j++) {
+			f1=d++;
+			f2 += twox;
+			pl[j]=(f2*pl[j-1]-f1*pl[j-2])/d;
+		}
+	}
+}