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diff --git a/third_party/rust/float-cmp/src/eq.rs b/third_party/rust/float-cmp/src/eq.rs
new file mode 100644
index 0000000000..d39535c95a
--- /dev/null
+++ b/third_party/rust/float-cmp/src/eq.rs
@@ -0,0 +1,284 @@
+// Copyright 2014-2018 Optimal Computing (NZ) Ltd.
+// Licensed under the MIT license.  See LICENSE for details.
+
+use std::{f32,f64};
+use super::Ulps;
+
+/// ApproxEq is a trait for approximate equality comparisons.
+pub trait ApproxEq: Sized {
+    /// The Margin type defines a margin within which two values are to be
+    /// considered approximately equal. It must implement Default so that
+    /// approx_eq() can be called on unknown types.
+    type Margin: Copy + Default;
+
+    /// This method tests for `self` and `other` values to be approximately equal
+    /// within `margin`.
+    fn approx_eq<M: Into<Self::Margin>>(self, other: Self, margin: M) -> bool;
+
+    /// This method tests for `self` and `other` values to be not approximately
+    /// equal within `margin`.
+    fn approx_ne<M: Into<Self::Margin>>(self, other: Self, margin: M) -> bool {
+        !self.approx_eq(other, margin)
+    }
+}
+
+/// This type defines a margin within two f32s might be considered equal
+/// and is intended as the associated type for the `ApproxEq` trait.
+///
+/// Two methods are used to determine approximate equality.
+///
+/// First an epsilon method is used, considering them approximately equal if they
+/// differ by <= `epsilon`.  This will only succeed for very small numbers.
+/// Note that it may succeed even if the parameters are of differing signs straddling
+/// zero.
+///
+/// The second method considers how many ULPs (units of least precision, units in
+/// the last place, which is the integer number of floating point representations
+/// that the parameters are separated by) different the parameters are and considers
+/// them approximately equal if this is <= `ulps`. For large floating point numbers,
+/// an ULP can be a rather large gap, but this kind of comparison is necessary
+/// because floating point operations must round to the nearest representable value
+/// and so larger floating point values accumulate larger errors.
+#[repr(C)]
+#[derive(Debug, Clone, Copy)]
+pub struct F32Margin {
+    pub epsilon: f32,
+    pub ulps: i32
+}
+impl Default for F32Margin {
+    #[inline]
+    fn default() -> F32Margin {
+        F32Margin {
+            epsilon: f32::EPSILON,
+            ulps: 4
+        }
+    }
+}
+impl F32Margin {
+    #[inline]
+    pub fn zero() -> F32Margin {
+        F32Margin {
+            epsilon: 0.0,
+            ulps: 0
+        }
+    }
+    pub fn epsilon(self, epsilon: f32) -> Self {
+        F32Margin {
+            epsilon: epsilon,
+            ..self
+        }
+    }
+    pub fn ulps(self, ulps: i32) -> Self {
+        F32Margin {
+            ulps: ulps,
+            ..self
+        }
+    }
+}
+impl From<(f32, i32)> for F32Margin {
+    fn from(m: (f32, i32)) -> F32Margin {
+        F32Margin {
+            epsilon: m.0,
+            ulps: m.1
+        }
+    }
+}
+
+impl ApproxEq for f32 {
+    type Margin = F32Margin;
+
+    fn approx_eq<M: Into<Self::Margin>>(self, other: f32, margin: M) -> bool {
+        let margin = margin.into();
+
+        // Check for exact equality first. This is often true, and so we get the
+        // performance benefit of only doing one compare in most cases.
+        self==other ||
+
+        // Perform epsilon comparison next
+            ((self - other).abs() <= margin.epsilon) ||
+
+        {
+            // Perform ulps comparion last
+            let diff: i32 = self.ulps(&other);
+            saturating_abs_i32!(diff) <= margin.ulps
+        }
+    }
+}
+
+#[test]
+fn f32_approx_eq_test1() {
+    let f: f32 = 0.0_f32;
+    let g: f32 = -0.0000000000000005551115123125783_f32;
+    assert!(f != g); // Should not be directly equal
+    assert!(f.approx_eq(g, (f32::EPSILON, 0)) == true);
+}
+#[test]
+fn f32_approx_eq_test2() {
+    let f: f32 = 0.0_f32;
+    let g: f32 = -0.0_f32;
+    assert!(f.approx_eq(g, (f32::EPSILON, 0)) == true);
+}
+#[test]
+fn f32_approx_eq_test3() {
+    let f: f32 = 0.0_f32;
+    let g: f32 = 0.00000000000000001_f32;
+    assert!(f.approx_eq(g, (f32::EPSILON, 0)) == true);
+}
+#[test]
+fn f32_approx_eq_test4() {
+    let f: f32 = 0.00001_f32;
+    let g: f32 = 0.00000000000000001_f32;
+    assert!(f.approx_eq(g, (f32::EPSILON, 0)) == false);
+}
+#[test]
+fn f32_approx_eq_test5() {
+    let f: f32 = 0.1_f32;
+    let mut sum: f32 = 0.0_f32;
+    for _ in 0_isize..10_isize { sum += f; }
+    let product: f32 = f * 10.0_f32;
+    assert!(sum != product); // Should not be directly equal:
+    println!("Ulps Difference: {}",sum.ulps(&product));
+    assert!(sum.approx_eq(product, (f32::EPSILON, 1)) == true);
+    assert!(sum.approx_eq(product, F32Margin::zero()) == false);
+}
+#[test]
+fn f32_approx_eq_test6() {
+    let x: f32 = 1000000_f32;
+    let y: f32 = 1000000.1_f32;
+    assert!(x != y); // Should not be directly equal
+    assert!(x.approx_eq(y, (0.0, 2)) == true); // 2 ulps does it
+    // epsilon method no good here:
+    assert!(x.approx_eq(y, (1000.0 * f32::EPSILON, 0)) == false);
+}
+
+/// This type defines a margin within two f32s might be considered equal
+/// and is intended as the associated type for the `ApproxEq` trait.
+///
+/// Two methods are used to determine approximate equality.
+///
+/// First an epsilon method is used, considering them approximately equal if they
+/// differ by <= `epsilon`.  This will only succeed for very small numbers.
+/// Note that it may succeed even if the parameters are of differing signs straddling
+/// zero.
+///
+/// The second method considers how many ULPs (units of least precision, units in
+/// the last place, which is the integer number of floating point representations
+/// that the parameters are separated by) different the parameters are and considers
+/// them approximately equal if this <= `ulps`. For large floating point numbers,
+/// an ULP can be a rather large gap, but this kind of comparison is necessary
+/// because floating point operations must round to the nearest representable value
+/// and so larger floating point values accumulate larger errors.
+#[derive(Debug, Clone, Copy)]
+pub struct F64Margin {
+    pub epsilon: f64,
+    pub ulps: i64
+}
+impl Default for F64Margin {
+    #[inline]
+    fn default() -> F64Margin {
+        F64Margin {
+            epsilon: f64::EPSILON,
+            ulps: 4
+        }
+    }
+}
+impl F64Margin {
+    #[inline]
+    pub fn zero() -> F64Margin {
+        F64Margin {
+            epsilon: 0.0,
+            ulps: 0
+        }
+    }
+    pub fn epsilon(self, epsilon: f64) -> Self {
+        F64Margin {
+            epsilon: epsilon,
+            ..self
+        }
+    }
+    pub fn ulps(self, ulps: i64) -> Self {
+        F64Margin {
+            ulps: ulps,
+            ..self
+        }
+    }
+}
+impl From<(f64, i64)> for F64Margin {
+    fn from(m: (f64, i64)) -> F64Margin {
+        F64Margin {
+            epsilon: m.0,
+            ulps: m.1
+        }
+    }
+}
+
+impl ApproxEq for f64 {
+    type Margin = F64Margin;
+
+    fn approx_eq<M: Into<Self::Margin>>(self, other: f64, margin: M) -> bool {
+        let margin = margin.into();
+
+        // Check for exact equality first. This is often true, and so we get the
+        // performance benefit of only doing one compare in most cases.
+        self==other ||
+
+        // Perform epsilon comparison next
+            ((self - other).abs() <= margin.epsilon) ||
+
+        {
+            // Perform ulps comparion last
+            let diff: i64 = self.ulps(&other);
+            saturating_abs_i64!(diff) <= margin.ulps
+        }
+    }
+}
+
+#[test]
+fn f64_approx_eq_test1() {
+    let f: f64 = 0.0_f64;
+    let g: f64 = -0.0000000000000005551115123125783_f64;
+    assert!(f != g); // Should not be directly equal
+    assert!(f.approx_eq(g, (3.0 * f64::EPSILON, 0)) == true); // 3e is enough
+    // ulps test wont ever call these equal
+}
+#[test]
+fn f64_approx_eq_test2() {
+    let f: f64 = 0.0_f64;
+    let g: f64 = -0.0_f64;
+    assert!(f.approx_eq(g, (f64::EPSILON, 0)) == true);
+}
+#[test]
+fn f64_approx_eq_test3() {
+    let f: f64 = 0.0_f64;
+    let g: f64 = 1e-17_f64;
+    assert!(f.approx_eq(g, (f64::EPSILON, 0)) == true);
+}
+#[test]
+fn f64_approx_eq_test4() {
+    let f: f64 = 0.00001_f64;
+    let g: f64 = 0.00000000000000001_f64;
+    assert!(f.approx_eq(g, (f64::EPSILON, 0)) == false);
+}
+#[test]
+fn f64_approx_eq_test5() {
+    let f: f64 = 0.1_f64;
+    let mut sum: f64 = 0.0_f64;
+    for _ in 0_isize..10_isize { sum += f; }
+    let product: f64 = f * 10.0_f64;
+    assert!(sum != product); // Should not be directly equal:
+    println!("Ulps Difference: {}",sum.ulps(&product));
+    assert!(sum.approx_eq(product, (f64::EPSILON, 0)) == true);
+    assert!(sum.approx_eq(product, (0.0, 1)) == true);
+}
+#[test]
+fn f64_approx_eq_test6() {
+    let x: f64 = 1000000_f64;
+    let y: f64 = 1000000.0000000003_f64;
+    assert!(x != y); // Should not be directly equal
+    println!("Ulps Difference: {}",x.ulps(&y));
+    assert!(x.approx_eq(y, (0.0, 3)) == true);
+}
+#[test]
+fn f64_code_triggering_issue_20() {
+    assert_eq!((-25.0f64).approx_eq(25.0, (0.00390625, 1)), false);
+}