Initial project import

tools/v/vlib/math/scalbn.v

@@ -0,0 +1,38 @@
+module math
+
+// scalbn scales x by FLT_RADIX raised to the power of n, returning the same as:
+// scalbn(x,n) = x * FLT_RADIX ** n
+pub fn scalbn(x f64, n_ int) f64 {
+	mut n := n_
+	x1p1023 := f64_from_bits(u64(0x7fe0000000000000))
+	x1p53 := f64_from_bits(u64(0x4340000000000000))
+	x1p_1022 := f64_from_bits(u64(0x0010000000000000))
+
+	mut y := x
+	if n > 1023 {
+		y *= x1p1023
+		n -= 1023
+		if n > 1023 {
+			y *= x1p1023
+			n -= 1023
+			if n > 1023 {
+				n = 1023
+			}
+		}
+	} else if n < -1022 {
+		/*
+		make sure final n < -53 to avoid double
+        rounding in the subnormal range
+		*/
+		y *= x1p_1022 * x1p53
+		n += 1022 - 53
+		if n < -1022 {
+			y *= x1p_1022 * x1p53
+			n += 1022 - 53
+			if n < -1022 {
+				n = -1022
+			}
+		}
+	}
+	return y * f64_from_bits(u64((0x3ff + n)) << 52)
+}