add numerical recipes library

lib/nr/ansi/recipes/hunt.c

@@ -0,0 +1,51 @@
+
+void hunt(float xx[], unsigned long n, float x, unsigned long *jlo)
+{
+	unsigned long jm,jhi,inc;
+	int ascnd;
+
+	ascnd=(xx[n] >= xx[1]);
+	if (*jlo <= 0 || *jlo > n) {
+		*jlo=0;
+		jhi=n+1;
+	} else {
+		inc=1;
+		if (x >= xx[*jlo] == ascnd) {
+			if (*jlo == n) return;
+			jhi=(*jlo)+1;
+			while (x >= xx[jhi] == ascnd) {
+				*jlo=jhi;
+				inc += inc;
+				jhi=(*jlo)+inc;
+				if (jhi > n) {
+					jhi=n+1;
+					break;
+				}
+			}
+		} else {
+			if (*jlo == 1) {
+				*jlo=0;
+				return;
+			}
+			jhi=(*jlo)--;
+			while (x < xx[*jlo] == ascnd) {
+				jhi=(*jlo);
+				inc <<= 1;
+				if (inc >= jhi) {
+					*jlo=0;
+					break;
+				}
+				else *jlo=jhi-inc;
+			}
+		}
+	}
+	while (jhi-(*jlo) != 1) {
+		jm=(jhi+(*jlo)) >> 1;
+		if (x >= xx[jm] == ascnd)
+			*jlo=jm;
+		else
+			jhi=jm;
+	}
+	if (x == xx[n]) *jlo=n-1;
+	if (x == xx[1]) *jlo=1;
+}