Make Uniform and its helper traits use arguments of type Borrow<X> rather than type X.

Author: sicking

src/distributions/uniform.rs

@@ -53,10 +53,17 @@
 //! Those methods should include an assert to check the range is valid (i.e.
 //! `low < high`). The example below merely wraps another back-end.
 //!
+//! The `new`, `new_inclusive` and `sample_single` functions use arguments of
+//! type Borrow<X> in order to support passing in values by reference or by
+//! value. In the implementation of these functions, you can choose to simply
+//! use the reference returned by `Borrow::borrow`, or you can choose to copy
+//! or clone the value, whatever is appropriate for your type.
+//!
 //! ```
 //! use rand::prelude::*;
 //! use rand::distributions::uniform::{Uniform, SampleUniform,
 //!         UniformSampler, UniformFloat};
+//! use std::borrow::Borrow;
 //!
 //! struct MyF32(f32);
 //!
@@ -67,12 +74,18 @@
 //!
 //! impl UniformSampler for UniformMyF32 {
 //!     type X = MyF32;
-//!     fn new(low: Self::X, high: Self::X) -> Self {
+//!     fn new<B1, B2>(low: B1, high: B2) -> Self
+//!         where B1: Borrow<Self::X> + Sized,
+//!               B2: Borrow<Self::X> + Sized
+//!     {
 //!         UniformMyF32 {
-//!             inner: UniformFloat::<f32>::new(low.0, high.0),
+//!             inner: UniformFloat::<f32>::new(low.borrow().0, high.borrow().0),
 //!         }
 //!     }
-//!     fn new_inclusive(low: Self::X, high: Self::X) -> Self {
+//!     fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
+//!         where B1: Borrow<Self::X> + Sized,
+//!               B2: Borrow<Self::X> + Sized
+//!     {
 //!         UniformSampler::new(low, high)
 //!     }
 //!     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
@@ -99,6 +112,7 @@
 
 #[cfg(feature = "std")]
 use std::time::Duration;
+use core::borrow::Borrow;
 
 use Rng;
 use distributions::Distribution;
@@ -155,13 +169,19 @@ pub struct Uniform<X: SampleUniform> {
 impl<X: SampleUniform> Uniform<X> {
     /// Create a new `Uniform` instance which samples uniformly from the half
     /// open range `[low, high)` (excluding `high`). Panics if `low >= high`.
-    pub fn new(low: X, high: X) -> Uniform<X> {
+    pub fn new<B1, B2>(low: B1, high: B2) -> Uniform<X>
+        where B1: Borrow<X> + Sized,
+              B2: Borrow<X> + Sized
+    {
         Uniform { inner: X::Sampler::new(low, high) }
     }
 
     /// Create a new `Uniform` instance which samples uniformly from the closed
     /// range `[low, high]` (inclusive). Panics if `low > high`.
-    pub fn new_inclusive(low: X, high: X) -> Uniform<X> {
+    pub fn new_inclusive<B1, B2>(low: B1, high: B2) -> Uniform<X>
+        where B1: Borrow<X> + Sized,
+              B2: Borrow<X> + Sized
+    {
         Uniform { inner: X::Sampler::new_inclusive(low, high) }
     }
 }
@@ -206,14 +226,18 @@ pub trait UniformSampler: Sized {
     ///
     /// Usually users should not call this directly but instead use
     /// `Uniform::new`, which asserts that `low < high` before calling this.
-    fn new(low: Self::X, high: Self::X) -> Self;
+    fn new<B1, B2>(low: B1, high: B2) -> Self
+        where B1: Borrow<Self::X> + Sized,
+              B2: Borrow<Self::X> + Sized;
 
     /// Construct self, with inclusive bounds `[low, high]`.
     ///
     /// Usually users should not call this directly but instead use
     /// `Uniform::new_inclusive`, which asserts that `low <= high` before
     /// calling this.
-    fn new_inclusive(low: Self::X, high: Self::X) -> Self;
+    fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
+        where B1: Borrow<Self::X> + Sized,
+              B2: Borrow<Self::X> + Sized;
 
     /// Sample a value.
     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X;
@@ -229,8 +253,10 @@ pub trait UniformSampler: Sized {
     /// sampling only a single value from the specified range. The default
     /// implementation simply calls `UniformSampler::new` then `sample` on the
     /// result.
-    fn sample_single<R: Rng + ?Sized>(low: Self::X, high: Self::X, rng: &mut R)
+    fn sample_single<R: Rng + ?Sized, B1, B2>(low: B1, high: B2, rng: &mut R)
         -> Self::X
+        where B1: Borrow<Self::X> + Sized,
+              B2: Borrow<Self::X> + Sized
     {
         let uniform: Self = UniformSampler::new(low, high);
         uniform.sample(rng)
@@ -311,14 +337,24 @@ macro_rules! uniform_int_impl {
 
             #[inline] // if the range is constant, this helps LLVM to do the
                       // calculations at compile-time.
-            fn new(low: Self::X, high: Self::X) -> Self {
+            fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
                 assert!(low < high, "Uniform::new called with `low >= high`");
                 UniformSampler::new_inclusive(low, high - 1)
             }
 
             #[inline] // if the range is constant, this helps LLVM to do the
                       // calculations at compile-time.
-            fn new_inclusive(low: Self::X, high: Self::X) -> Self {
+            fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
                 assert!(low <= high,
                         "Uniform::new_inclusive called with `low > high`");
                 let unsigned_max = ::core::$unsigned::MAX;
@@ -362,10 +398,13 @@ macro_rules! uniform_int_impl {
                 }
             }
 
-            fn sample_single<R: Rng + ?Sized>(low: Self::X,
-                                              high: Self::X,
-                                              rng: &mut R) -> Self::X
+            fn sample_single<R: Rng + ?Sized, B1, B2>(low_b: B1, high_b: B2, rng: &mut R)
+                -> Self::X
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
             {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
                 assert!(low < high,
                         "Uniform::sample_single called with low >= high");
                 let range = high.wrapping_sub(low) as $unsigned as $u_large;
@@ -532,7 +571,12 @@ macro_rules! uniform_float_impl {
         impl UniformSampler for UniformFloat<$ty> {
             type X = $ty;
 
-            fn new(low: Self::X, high: Self::X) -> Self {
+            fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
                 assert!(low < high, "Uniform::new called with `low >= high`");
                 let scale = high - low;
                 let offset = low - scale;
@@ -542,7 +586,12 @@ macro_rules! uniform_float_impl {
                 }
             }
 
-            fn new_inclusive(low: Self::X, high: Self::X) -> Self {
+            fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
                 assert!(low <= high,
                         "Uniform::new_inclusive called with `low > high`");
                 let scale = high - low;
@@ -565,9 +614,13 @@ macro_rules! uniform_float_impl {
                 value1_2 * self.scale + self.offset
             }
 
-            fn sample_single<R: Rng + ?Sized>(low: Self::X,
-                                              high: Self::X,
-                                              rng: &mut R) -> Self::X {
+            fn sample_single<R: Rng + ?Sized, B1, B2>(low_b: B1, high_b: B2, rng: &mut R)
+                -> Self::X
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
                 assert!(low < high,
                         "Uniform::sample_single called with low >= high");
                 let scale = high - low;
@@ -624,13 +677,23 @@ impl UniformSampler for UniformDuration {
     type X = Duration;
 
     #[inline]
-    fn new(low: Duration, high: Duration) -> UniformDuration {
+    fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+        where B1: Borrow<Self::X> + Sized,
+              B2: Borrow<Self::X> + Sized
+    {
+        let low = *low_b.borrow();
+        let high = *high_b.borrow();
         assert!(low < high, "Uniform::new called with `low >= high`");
         UniformDuration::new_inclusive(low, high - Duration::new(0, 1))
     }
 
     #[inline]
-    fn new_inclusive(low: Duration, high: Duration) -> UniformDuration {
+    fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+        where B1: Borrow<Self::X> + Sized,
+              B2: Borrow<Self::X> + Sized
+    {
+        let low = *low_b.borrow();
+        let high = *high_b.borrow();
         assert!(low <= high, "Uniform::new_inclusive called with `low > high`");
         let size = high - low;
         let nanos = size
@@ -750,6 +813,18 @@ mod tests {
                             assert!(low <= v && v <= high);
                         }
 
+                        let my_uniform = Uniform::new(&low, high);
+                        for _ in 0..1000 {
+                            let v: $ty = rng.sample(my_uniform);
+                            assert!(low <= v && v < high);
+                        }
+
+                        let my_uniform = Uniform::new_inclusive(&low, &high);
+                        for _ in 0..1000 {
+                            let v: $ty = rng.sample(my_uniform);
+                            assert!(low <= v && v <= high);
+                        }
+
                         for _ in 0..1000 {
                             let v: $ty = rng.gen_range(low, high);
                             assert!(low <= v && v < high);
@@ -809,6 +884,7 @@ mod tests {
 
     #[test]
     fn test_custom_uniform() {
+        use core::borrow::Borrow;
         #[derive(Clone, Copy, PartialEq, PartialOrd)]
         struct MyF32 {
             x: f32,
@@ -819,12 +895,18 @@ mod tests {
         }
         impl UniformSampler for UniformMyF32 {
             type X = MyF32;
-            fn new(low: Self::X, high: Self::X) -> Self {
+            fn new<B1, B2>(low: B1, high: B2) -> Self
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
                 UniformMyF32 {
-                    inner: UniformFloat::<f32>::new(low.x, high.x),
+                    inner: UniformFloat::<f32>::new(low.borrow().x, high.borrow().x),
                 }
             }
-            fn new_inclusive(low: Self::X, high: Self::X) -> Self {
+            fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
+                where B1: Borrow<Self::X> + Sized,
+                      B2: Borrow<Self::X> + Sized
+            {
                 UniformSampler::new(low, high)
             }
             fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {

src/lib.rs

@@ -300,10 +300,10 @@ pub mod isaac {
 
 
 use core::{mem, slice};
+use core::borrow::Borrow;
 use distributions::{Distribution, Standard};
 use distributions::uniform::{SampleUniform, UniformSampler};
 
-
 /// An automatically-implemented extension trait on [`RngCore`] providing high-level
 /// generic methods for sampling values and other convenience methods.
 /// 
@@ -387,7 +387,9 @@ pub trait Rng: RngCore {
     /// ```
     ///
     /// [`Uniform`]: distributions/uniform/struct.Uniform.html
-    fn gen_range<T: SampleUniform>(&mut self, low: T, high: T) -> T {
+    fn gen_range<T: SampleUniform, B1, B2>(&mut self, low: B1, high: B2) -> T
+        where B1: Borrow<T> + Sized,
+              B2: Borrow<T> + Sized {
         T::Sampler::sample_single(low, high, self)
     }
 
@@ -935,19 +937,19 @@ mod test {
     fn test_gen_range() {
         let mut r = rng(101);
         for _ in 0..1000 {
-            let a = r.gen_range(-3, 42);
-            assert!(a >= -3 && a < 42);
-            assert_eq!(r.gen_range(0, 1), 0);
-            assert_eq!(r.gen_range(-12, -11), -12);
-        }
-
-        for _ in 0..1000 {
-            let a = r.gen_range(10, 42);
-            assert!(a >= 10 && a < 42);
-            assert_eq!(r.gen_range(0, 1), 0);
+            let a = r.gen_range(-4711, 17);
+            assert!(a >= -4711 && a < 17);
+            let a = r.gen_range(-3i8, 42);
+            assert!(a >= -3i8 && a < 42i8);
+            let a = r.gen_range(&10u16, 99);
+            assert!(a >= 10u16 && a < 99u16);
+            let a = r.gen_range(-100i32, &2000);
+            assert!(a >= -100i32 && a < 2000i32);
+
+            assert_eq!(r.gen_range(0u32, 1), 0u32);
+            assert_eq!(r.gen_range(-12i64, -11), -12i64);
             assert_eq!(r.gen_range(3_000_000, 3_000_001), 3_000_000);
         }
-
     }
 
     #[test]