From 580a62daaf06170d3fc6b2e3d9a5fc288a81388a Mon Sep 17 00:00:00 2001
From: Stephen Chung <Stephen.Chung@intexact.com>
Date: Thu, 25 Jun 2020 19:19:16 +0800
Subject: [PATCH] Add sign function.

---
 doc/src/language/num-fn.md |  9 +++++----
 src/packages/arithmetic.rs | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/doc/src/language/num-fn.md b/doc/src/language/num-fn.md
index c6df7900..1e415e11 100644
--- a/doc/src/language/num-fn.md
+++ b/doc/src/language/num-fn.md
@@ -9,10 +9,11 @@ Integer Functions
 The following standard functions (defined in the [`BasicMathPackage`]({{rootUrl}}/rust/packages.md) but excluded if using a [raw `Engine`])
 operate on `i8`, `i16`, `i32`, `i64`, `f32` and `f64` only:
 
-| Function     | Description                       |
-| ------------ | --------------------------------- |
-| `abs`        | absolute value                    |
-| [`to_float`] | converts an integer type to `f64` |
+| Function     | Description                                                     |
+| ------------ | --------------------------------------------------------------- |
+| `abs`        | absolute value                                                  |
+| `sign`       | returns -1 if the number is negative, +1 if positive, 0 if zero |
+| [`to_float`] | converts an integer type to `f64`                               |
 
 Floating-Point Functions
 -----------------------
diff --git a/src/packages/arithmetic.rs b/src/packages/arithmetic.rs
index cf109b0c..31808a2a 100644
--- a/src/packages/arithmetic.rs
+++ b/src/packages/arithmetic.rs
@@ -267,6 +267,19 @@ macro_rules! reg_op {
         $( $lib.set_fn_2($op, $func::<$par>); )*
     };
 }
+macro_rules! reg_sign {
+    ($lib:expr, $op:expr, $ret:ty, $($par:ty),*) => {
+        $( $lib.set_fn_1($op, |value: $par| -> Result<$ret, _> {
+            Ok(if value == (0 as $par) {
+                (0 as $ret)
+            } else if value < (0 as $par) {
+                (-1 as $ret)
+            } else {
+                (1 as $ret)
+            })
+        }); )*
+    };
+}
 
 def_package!(crate:ArithmeticPackage:"Basic arithmetic", lib, {
     #[cfg(not(feature = "only_i32"))]
@@ -321,6 +334,11 @@ def_package!(crate:ArithmeticPackage:"Basic arithmetic", lib, {
                 reg_op!(lib, "%", modulo_u, i128, u128);
             }
         }
+
+        reg_sign!(lib, "sign", INT, i8, i16, i32, i64);
+
+        #[cfg(not(target_arch = "wasm32"))]
+        reg_sign!(lib, "sign", INT, i128);
     }
 
     // Basic arithmetic for floating-point - no need to check
@@ -330,6 +348,8 @@ def_package!(crate:ArithmeticPackage:"Basic arithmetic", lib, {
         reg_op!(lib, "-", sub_u, f32);
         reg_op!(lib, "*", mul_u, f32);
         reg_op!(lib, "/", div_u, f32);
+        reg_sign!(lib, "sign", f32, f32);
+        reg_sign!(lib, "sign", f64, f64);
     }
 
     #[cfg(not(feature = "only_i32"))]