move out sign

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/util/sign.h

@@ -0,0 +1,24 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    sign.h
+
+Abstract:
+
+    Sign
+
+Author:
+
+    Nikolaj Bjorner
+
+--*/
+
+#pragma once
+
+typedef enum { sign_neg = -1, sign_zero = 0, sign_pos = 1} sign;
+inline sign operator-(sign s) { switch (s) { case sign_neg: return sign_pos; case sign_pos: return sign_neg; default: return sign_zero; } };
+inline sign to_sign(int s) { return s == 0 ? sign_zero : (s > 0 ? sign_pos : sign_neg); }
+inline sign operator*(sign a, sign b) { return to_sign((int)a * (int)b); }
+inline bool is_zero(sign s) { return s == sign_zero; }