From 39ac651a9f7039badcf3326cfac89b6b3f712be1 Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Fri, 13 Jul 2018 00:40:05 +0000
Subject: [PATCH 1/3] Implement `round`

---
 src/lib.rs                 |  6 ++++++
 src/math/mod.rs            |  2 ++
 src/math/round.rs          | 35 +++++++++++++++++++++++++++++++++++
 test-generator/src/main.rs |  2 +-
 4 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 src/math/round.rs

diff --git a/src/lib.rs b/src/lib.rs
index fc9628d..f54366b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,6 +12,12 @@
 #![deny(warnings)]
 #![no_std]
 
+macro_rules! force_eval {
+    ($e:expr) => {
+        unsafe { ::core::ptr::read_volatile(&$e); }
+    }
+}
+
 mod math;
 
 #[cfg(todo)]
diff --git a/src/math/mod.rs b/src/math/mod.rs
index 09d8194..c150a62 100644
--- a/src/math/mod.rs
+++ b/src/math/mod.rs
@@ -2,6 +2,7 @@ mod fabs;
 mod fabsf;
 mod fmodf;
 mod powf;
+mod round;
 mod scalbnf;
 mod sqrtf;
 
@@ -9,6 +10,7 @@ pub use self::fabs::fabs;
 pub use self::fabsf::fabsf;
 pub use self::fmodf::fmodf;
 pub use self::powf::powf;
+pub use self::round::round;
 pub use self::scalbnf::scalbnf;
 pub use self::sqrtf::sqrtf;
 
diff --git a/src/math/round.rs b/src/math/round.rs
new file mode 100644
index 0000000..2a9f67c
--- /dev/null
+++ b/src/math/round.rs
@@ -0,0 +1,35 @@
+use core::f64;
+
+const TOINT: f64 = 1.0 / f64::EPSILON;
+
+pub fn round(mut x: f64) -> f64 {
+    let (f, i) = (x, x.to_bits());
+    let e: u64 = i >> 52 & 0x7ff;
+    let mut y: f64;
+
+    if e >= 0x3ff + 52 {
+        return x;
+    }
+    if i >> 63 != 0 {
+        x = -x;
+    }
+    if e < 0x3ff - 1 {
+        // raise inexact if x!=0
+        force_eval!(x + TOINT);
+        return 0.0 * f;
+    }
+    y = x + TOINT - TOINT - x;
+    if y > 0.5 {
+        y = y + x - 1.0;
+    } else if y <= -0.5 {
+        y = y + x + 1.0;
+    } else {
+        y = y + x;
+    }
+    
+    if i >> 63 != 0 {
+        -y
+    } else {
+        y
+    }
+}
diff --git a/test-generator/src/main.rs b/test-generator/src/main.rs
index a13aa4e..5ff78ff 100644
--- a/test-generator/src/main.rs
+++ b/test-generator/src/main.rs
@@ -618,7 +618,7 @@ f64_f64! {
     // log10,
     // log1p,
     // log2,
-    // round,
+    round,
     // sin,
     // sinh,
     // sqrt,

From ac9e81b9c59ff4a517a1c3df55ff9a7f39d51c0f Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Fri, 13 Jul 2018 01:25:46 +0000
Subject: [PATCH 2/3] Enable f64::round

---
 src/lib.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index f54366b..06ef459 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -383,7 +383,6 @@ pub trait F64Ext {
     #[cfg(todo)]
     fn ceil(self) -> Self;
 
-    #[cfg(todo)]
     fn round(self) -> Self;
 
     #[cfg(todo)]
@@ -504,7 +503,6 @@ impl F64Ext for f64 {
         ceil(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn round(self) -> Self {
         round(self)

From dd2bbcb89033bf1aff43f7edb35edc464535ae87 Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Fri, 13 Jul 2018 01:38:04 +0000
Subject: [PATCH 3/3] Move the `force_eval!` macro into the math module

This fixes the cross-inclusion into the compiler builtins
---
 src/lib.rs      | 6 ------
 src/math/mod.rs | 6 ++++++
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 06ef459..0d13590 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,12 +12,6 @@
 #![deny(warnings)]
 #![no_std]
 
-macro_rules! force_eval {
-    ($e:expr) => {
-        unsafe { ::core::ptr::read_volatile(&$e); }
-    }
-}
-
 mod math;
 
 #[cfg(todo)]
diff --git a/src/math/mod.rs b/src/math/mod.rs
index c150a62..41359bf 100644
--- a/src/math/mod.rs
+++ b/src/math/mod.rs
@@ -1,3 +1,9 @@
+macro_rules! force_eval {
+    ($e:expr) => {
+        unsafe { ::core::ptr::read_volatile(&$e); }
+    }
+}
+
 mod fabs;
 mod fabsf;
 mod fmodf;