add numerical recipes library

lib/nr/ansi/recipes/banbks.c

@@ -0,0 +1,27 @@
+
+#define SWAP(a,b) {dum=(a);(a)=(b);(b)=dum;}
+
+void banbks(float **a, unsigned long n, int m1, int m2, float **al,
+	unsigned long indx[], float b[])
+{
+	unsigned long i,k,l;
+	int mm;
+	float dum;
+
+	mm=m1+m2+1;
+	l=m1;
+	for (k=1;k<=n;k++) {
+		i=indx[k];
+		if (i != k) SWAP(b[k],b[i])
+		if (l < n) l++;
+		for (i=k+1;i<=l;i++) b[i] -= al[k][i-k]*b[k];
+	}
+	l=1;
+	for (i=n;i>=1;i--) {
+		dum=b[i];
+		for (k=2;k<=l;k++) dum -= a[i][k]*b[k+i-1];
+		b[i]=dum/a[i][1];
+		if (l < mm) l++;
+	}
+}
+#undef SWAP