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// Copyright 2013 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 char;
use int;
use option::{Option, Some, None};
use rand::{Rand,Rng};
use uint;
impl Rand for int {
#[inline]
fn rand<R: Rng>(rng: &mut R) -> int {
if int::bits == 32 {
rng.gen::<i32>() as int
} else {
rng.gen::<i64>() as int
}
}
}
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
}
}
impl Rand for uint {
#[inline]
fn rand<R: Rng>(rng: &mut R) -> uint {
if uint::bits == 32 {
rng.gen::<u32>() as uint
} else {
rng.gen::<u64>() as uint
}
}
}
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()
}
}
impl Rand for f32 {
/// A random `f32` in the range `[0, 1)`, using 24 bits of
/// precision.
#[inline]
fn rand<R: Rng>(rng: &mut R) -> f32 {
// using any more than 24 bits will cause (e.g.) 0xffff_ffff
// to correspond to 1 exactly, so we need to drop 8 to
// guarantee the open end.
static SCALE: f32 = (1u32 << 24) as f32;
(rng.next_u32() >> 8) as f32 / SCALE
}
}
impl Rand for f64 {
/// A random `f64` in the range `[0, 1)`, using 53 bits of
/// precision.
#[inline]
fn rand<R: Rng>(rng: &mut R) -> f64 {
// as for f32, but using more bits.
static SCALE: f64 = (1u64 << 53) as f64;
(rng.next_u64() >> 11) as f64 / SCALE
}
}
impl Rand for char {
#[inline]
fn rand<R: Rng>(rng: &mut R) -> char {
// a char is 21 bits
static 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}
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
}
}
}
impl<T: Rand> Rand for ~T {
#[inline]
fn rand<R: Rng>(rng: &mut R) -> ~T { ~rng.gen() }
}
impl<T: Rand + 'static> Rand for @T {
#[inline]
fn rand<R: Rng>(rng: &mut R) -> @T { @rng.gen() }
}
#[cfg(test)]
mod tests {
use rand::Rng;
struct ConstantRng(u64);
impl Rng for ConstantRng {
fn next_u32(&mut self) -> u32 {
(**self) as u32
}
fn next_u64(&mut self) -> u64 {
**self
}
}
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)
}
}
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