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Introduce a float_impl! macro to avoid duplication

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est31 2017-09-13 22:44:56 +02:00
parent 9bdedec38e
commit 46cfa05650
1 changed files with 36 additions and 64 deletions
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50
src/float/mod.rs
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@ -60,10 +60,12 @@ pub trait Float: Sized + Copy {
// FIXME: Some of this can be removed if RFC Issue #1424 is resolved // FIXME: Some of this can be removed if RFC Issue #1424 is resolved
// https://github.com/rust-lang/rfcs/issues/1424 // https://github.com/rust-lang/rfcs/issues/1424
impl Float for f32 { macro_rules! float_impl {
type Int = u32; ($ty:ident, $ity:ident, $bits:expr, $significand_bits:expr) => {
const BITS: u32 = 32; impl Float for $ty {
const SIGNIFICAND_BITS: u32 = 23; type Int = $ity;
const BITS: u32 = $bits;
const SIGNIFICAND_BITS: u32 = $significand_bits;
const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1); const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1);
const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1; const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1;
@ -91,42 +93,12 @@ impl Float for f32 {
} }
fn normalize(significand: Self::Int) -> (i32, Self::Int) { fn normalize(significand: Self::Int) -> (i32, Self::Int) {
let shift = significand.leading_zeros() let shift = significand.leading_zeros()
.wrapping_sub((1u32 << Self::SIGNIFICAND_BITS).leading_zeros()); .wrapping_sub((Self::Int::ONE << Self::SIGNIFICAND_BITS).leading_zeros());
(1i32.wrapping_sub(shift as i32), significand << shift as Self::Int) (1i32.wrapping_sub(shift as i32), significand << shift as Self::Int)
} }
} }
impl Float for f64 { }
type Int = u64; }
const BITS: u32 = 64;
const SIGNIFICAND_BITS: u32 = 52;
const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1); float_impl!(f32, u32, 32, 23);
const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1; float_impl!(f64, u64, 64, 52);
const IMPLICIT_BIT: Self::Int = 1 << Self::SIGNIFICAND_BITS;
const EXPONENT_MASK: Self::Int = !(Self::SIGN_MASK | Self::SIGNIFICAND_MASK);
fn repr(self) -> Self::Int {
unsafe { mem::transmute(self) }
}
#[cfg(test)]
fn eq_repr(self, rhs: Self) -> bool {
if self.is_nan() && rhs.is_nan() {
true
} else {
self.repr() == rhs.repr()
}
}
fn from_repr(a: Self::Int) -> Self {
unsafe { mem::transmute(a) }
}
fn from_parts(sign: bool, exponent: Self::Int, significand: Self::Int) -> Self {
Self::from_repr(((sign as Self::Int) << (Self::BITS - 1)) |
((exponent << Self::SIGNIFICAND_BITS) & Self::EXPONENT_MASK) |
(significand & Self::SIGNIFICAND_MASK))
}
fn normalize(significand: Self::Int) -> (i32, Self::Int) {
let shift = significand.leading_zeros()
.wrapping_sub((1u64 << Self::SIGNIFICAND_BITS).leading_zeros());
(1i32.wrapping_sub(shift as i32), significand << shift as Self::Int)
}
}