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+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The implementations of `Rand` for the built-in types.
+
+use core::{char, mem};
+
+use {Rand,Rng};
+
+impl Rand for isize {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> isize {
+ if mem::size_of::<isize>() == 4 {
+ rng.gen::<i32>() as isize
+ } else {
+ rng.gen::<i64>() as isize
+ }
+ }
+}
+
+impl Rand for i8 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> i8 {
+ rng.next_u32() as i8
+ }
+}
+
+impl Rand for i16 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> i16 {
+ rng.next_u32() as i16
+ }
+}
+
+impl Rand for i32 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> i32 {
+ rng.next_u32() as i32
+ }
+}
+
+impl Rand for i64 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> i64 {
+ rng.next_u64() as i64
+ }
+}
+
+#[cfg(feature = "i128_support")]
+impl Rand for i128 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> i128 {
+ rng.gen::<u128>() as i128
+ }
+}
+
+impl Rand for usize {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> usize {
+ if mem::size_of::<usize>() == 4 {
+ rng.gen::<u32>() as usize
+ } else {
+ rng.gen::<u64>() as usize
+ }
+ }
+}
+
+impl Rand for u8 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> u8 {
+ rng.next_u32() as u8
+ }
+}
+
+impl Rand for u16 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> u16 {
+ rng.next_u32() as u16
+ }
+}
+
+impl Rand for u32 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> u32 {
+ rng.next_u32()
+ }
+}
+
+impl Rand for u64 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> u64 {
+ rng.next_u64()
+ }
+}
+
+#[cfg(feature = "i128_support")]
+impl Rand for u128 {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> u128 {
+ ((rng.next_u64() as u128) << 64) | (rng.next_u64() as u128)
+ }
+}
+
+
+macro_rules! float_impls {
+ ($mod_name:ident, $ty:ty, $mantissa_bits:expr, $method_name:ident) => {
+ mod $mod_name {
+ use {Rand, Rng, Open01, Closed01};
+
+ const SCALE: $ty = (1u64 << $mantissa_bits) as $ty;
+
+ impl Rand for $ty {
+ /// Generate a floating point number in the half-open
+ /// interval `[0,1)`.
+ ///
+ /// See `Closed01` for the closed interval `[0,1]`,
+ /// and `Open01` for the open interval `(0,1)`.
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> $ty {
+ rng.$method_name()
+ }
+ }
+ impl Rand for Open01<$ty> {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> Open01<$ty> {
+ // add a small amount (specifically 2 bits below
+ // the precision of f64/f32 at 1.0), so that small
+ // numbers are larger than 0, but large numbers
+ // aren't pushed to/above 1.
+ Open01(rng.$method_name() + 0.25 / SCALE)
+ }
+ }
+ impl Rand for Closed01<$ty> {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> Closed01<$ty> {
+ // rescale so that 1.0 - epsilon becomes 1.0
+ // precisely.
+ Closed01(rng.$method_name() * SCALE / (SCALE - 1.0))
+ }
+ }
+ }
+ }
+}
+float_impls! { f64_rand_impls, f64, 53, next_f64 }
+float_impls! { f32_rand_impls, f32, 24, next_f32 }
+
+impl Rand for char {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> char {
+ // a char is 21 bits
+ const CHAR_MASK: u32 = 0x001f_ffff;
+ loop {
+ // Rejection sampling. About 0.2% of numbers with at most
+ // 21-bits are invalid codepoints (surrogates), so this
+ // will succeed first go almost every time.
+ match char::from_u32(rng.next_u32() & CHAR_MASK) {
+ Some(c) => return c,
+ None => {}
+ }
+ }
+ }
+}
+
+impl Rand for bool {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> bool {
+ rng.gen::<u8>() & 1 == 1
+ }
+}
+
+macro_rules! tuple_impl {
+ // use variables to indicate the arity of the tuple
+ ($($tyvar:ident),* ) => {
+ // the trailing commas are for the 1 tuple
+ impl<
+ $( $tyvar : Rand ),*
+ > Rand for ( $( $tyvar ),* , ) {
+
+ #[inline]
+ fn rand<R: Rng>(_rng: &mut R) -> ( $( $tyvar ),* , ) {
+ (
+ // use the $tyvar's to get the appropriate number of
+ // repeats (they're not actually needed)
+ $(
+ _rng.gen::<$tyvar>()
+ ),*
+ ,
+ )
+ }
+ }
+ }
+}
+
+impl Rand for () {
+ #[inline]
+ fn rand<R: Rng>(_: &mut R) -> () { () }
+}
+tuple_impl!{A}
+tuple_impl!{A, B}
+tuple_impl!{A, B, C}
+tuple_impl!{A, B, C, D}
+tuple_impl!{A, B, C, D, E}
+tuple_impl!{A, B, C, D, E, F}
+tuple_impl!{A, B, C, D, E, F, G}
+tuple_impl!{A, B, C, D, E, F, G, H}
+tuple_impl!{A, B, C, D, E, F, G, H, I}
+tuple_impl!{A, B, C, D, E, F, G, H, I, J}
+tuple_impl!{A, B, C, D, E, F, G, H, I, J, K}
+tuple_impl!{A, B, C, D, E, F, G, H, I, J, K, L}
+
+macro_rules! array_impl {
+ {$n:expr, $t:ident, $($ts:ident,)*} => {
+ array_impl!{($n - 1), $($ts,)*}
+
+ impl<T> Rand for [T; $n] where T: Rand {
+ #[inline]
+ fn rand<R: Rng>(_rng: &mut R) -> [T; $n] {
+ [_rng.gen::<$t>(), $(_rng.gen::<$ts>()),*]
+ }
+ }
+ };
+ {$n:expr,} => {
+ impl<T> Rand for [T; $n] {
+ fn rand<R: Rng>(_rng: &mut R) -> [T; $n] { [] }
+ }
+ };
+}
+
+array_impl!{32, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,}
+
+impl<T:Rand> Rand for Option<T> {
+ #[inline]
+ fn rand<R: Rng>(rng: &mut R) -> Option<T> {
+ if rng.gen() {
+ Some(rng.gen())
+ } else {
+ None
+ }
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use {Rng, thread_rng, Open01, Closed01};
+
+ struct ConstantRng(u64);
+ impl Rng for ConstantRng {
+ fn next_u32(&mut self) -> u32 {
+ let ConstantRng(v) = *self;
+ v as u32
+ }
+ fn next_u64(&mut self) -> u64 {
+ let ConstantRng(v) = *self;
+ v
+ }
+ }
+
+ #[test]
+ fn floating_point_edge_cases() {
+ // the test for exact equality is correct here.
+ assert!(ConstantRng(0xffff_ffff).gen::<f32>() != 1.0);
+ assert!(ConstantRng(0xffff_ffff_ffff_ffff).gen::<f64>() != 1.0);
+ }
+
+ #[test]
+ fn rand_open() {
+ // this is unlikely to catch an incorrect implementation that
+ // generates exactly 0 or 1, but it keeps it sane.
+ let mut rng = thread_rng();
+ for _ in 0..1_000 {
+ // strict inequalities
+ let Open01(f) = rng.gen::<Open01<f64>>();
+ assert!(0.0 < f && f < 1.0);
+
+ let Open01(f) = rng.gen::<Open01<f32>>();
+ assert!(0.0 < f && f < 1.0);
+ }
+ }
+
+ #[test]
+ fn rand_closed() {
+ let mut rng = thread_rng();
+ for _ in 0..1_000 {
+ // strict inequalities
+ let Closed01(f) = rng.gen::<Closed01<f64>>();
+ assert!(0.0 <= f && f <= 1.0);
+
+ let Closed01(f) = rng.gen::<Closed01<f32>>();
+ assert!(0.0 <= f && f <= 1.0);
+ }
+ }
+}
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