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Improve format float #39615

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Feb 9, 2017
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Improve format float #39615

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94 changes: 94 additions & 0 deletions src/libcore/fmt/float.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,94 @@
// Copyright 2017 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.

use fmt::{Formatter, Result, LowerExp, UpperExp, Display, Debug};
use num::flt2dec;

// Common code of floating point Debug and Display.
fn float_to_decimal_common<T>(fmt: &mut Formatter, num: &T, negative_zero: bool) -> Result
where T: flt2dec::DecodableFloat
{
let force_sign = fmt.sign_plus();
let sign = match (force_sign, negative_zero) {
(false, false) => flt2dec::Sign::Minus,
(false, true) => flt2dec::Sign::MinusRaw,
(true, false) => flt2dec::Sign::MinusPlus,
(true, true) => flt2dec::Sign::MinusPlusRaw,
};

let mut buf = [0; 1024]; // enough for f32 and f64
let mut parts = [flt2dec::Part::Zero(0); 16];
let formatted = if let Some(precision) = fmt.precision {
flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact, *num, sign,
precision, false, &mut buf, &mut parts)
} else {
flt2dec::to_shortest_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
0, false, &mut buf, &mut parts)
};
fmt.pad_formatted_parts(&formatted)
}

// Common code of floating point LowerExp and UpperExp.
fn float_to_exponential_common<T>(fmt: &mut Formatter, num: &T, upper: bool) -> Result
where T: flt2dec::DecodableFloat
{
let force_sign = fmt.sign_plus();
let sign = match force_sign {
false => flt2dec::Sign::Minus,
true => flt2dec::Sign::MinusPlus,
};

let mut buf = [0; 1024]; // enough for f32 and f64
let mut parts = [flt2dec::Part::Zero(0); 16];
let formatted = if let Some(precision) = fmt.precision {
// 1 integral digit + `precision` fractional digits = `precision + 1` total digits
flt2dec::to_exact_exp_str(flt2dec::strategy::grisu::format_exact, *num, sign,
precision + 1, upper, &mut buf, &mut parts)
} else {
flt2dec::to_shortest_exp_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
(0, 0), upper, &mut buf, &mut parts)
};
fmt.pad_formatted_parts(&formatted)
}

macro_rules! floating {
($ty:ident) => (
#[stable(feature = "rust1", since = "1.0.0")]
impl Debug for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_decimal_common(fmt, self, true)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl Display for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_decimal_common(fmt, self, false)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl LowerExp for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_exponential_common(fmt, self, false)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl UpperExp for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_exponential_common(fmt, self, true)
}
}
)
}

floating! { f32 }
floating! { f64 }
87 changes: 4 additions & 83 deletions src/libcore/fmt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,10 @@ use result;
use slice;
use str;

mod float;
mod num;
mod builders;

#[unstable(feature = "fmt_flags_align", issue = "27726")]
/// Possible alignments returned by `Formatter::align`
#[derive(Debug)]
Expand All @@ -38,9 +42,6 @@ pub enum Alignment {
#[stable(feature = "debug_builders", since = "1.2.0")]
pub use self::builders::{DebugStruct, DebugTuple, DebugSet, DebugList, DebugMap};

mod num;
mod builders;

#[unstable(feature = "fmt_internals", reason = "internal to format_args!",
issue = "0")]
#[doc(hidden)]
Expand Down Expand Up @@ -1511,86 +1512,6 @@ impl<'a, T: ?Sized> Pointer for &'a mut T {
}
}

// Common code of floating point Debug and Display.
fn float_to_decimal_common<T>(fmt: &mut Formatter, num: &T, negative_zero: bool) -> Result
where T: flt2dec::DecodableFloat
{
let force_sign = fmt.sign_plus();
let sign = match (force_sign, negative_zero) {
(false, false) => flt2dec::Sign::Minus,
(false, true) => flt2dec::Sign::MinusRaw,
(true, false) => flt2dec::Sign::MinusPlus,
(true, true) => flt2dec::Sign::MinusPlusRaw,
};

let mut buf = [0; 1024]; // enough for f32 and f64
let mut parts = [flt2dec::Part::Zero(0); 16];
let formatted = if let Some(precision) = fmt.precision {
flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact, *num, sign,
precision, false, &mut buf, &mut parts)
} else {
flt2dec::to_shortest_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
0, false, &mut buf, &mut parts)
};
fmt.pad_formatted_parts(&formatted)
}

// Common code of floating point LowerExp and UpperExp.
fn float_to_exponential_common<T>(fmt: &mut Formatter, num: &T, upper: bool) -> Result
where T: flt2dec::DecodableFloat
{
let force_sign = fmt.sign_plus();
let sign = match force_sign {
false => flt2dec::Sign::Minus,
true => flt2dec::Sign::MinusPlus,
};

let mut buf = [0; 1024]; // enough for f32 and f64
let mut parts = [flt2dec::Part::Zero(0); 16];
let formatted = if let Some(precision) = fmt.precision {
// 1 integral digit + `precision` fractional digits = `precision + 1` total digits
flt2dec::to_exact_exp_str(flt2dec::strategy::grisu::format_exact, *num, sign,
precision + 1, upper, &mut buf, &mut parts)
} else {
flt2dec::to_shortest_exp_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
(0, 0), upper, &mut buf, &mut parts)
};
fmt.pad_formatted_parts(&formatted)
}

macro_rules! floating { ($ty:ident) => {

#[stable(feature = "rust1", since = "1.0.0")]
impl Debug for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_decimal_common(fmt, self, true)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl Display for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_decimal_common(fmt, self, false)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl LowerExp for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_exponential_common(fmt, self, false)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl UpperExp for $ty {
fn fmt(&self, fmt: &mut Formatter) -> Result {
float_to_exponential_common(fmt, self, true)
}
}
} }
floating! { f32 }
floating! { f64 }

// Implementation of Display/Debug for various core types

#[stable(feature = "rust1", since = "1.0.0")]
Expand Down
32 changes: 25 additions & 7 deletions src/libcoretest/fmt/float.rs
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Expand Up @@ -9,11 +9,29 @@
// except according to those terms.

#[test]
fn test_format_float() {
assert!("1" == format!("{:.0}", 1.0f64));
assert!("9" == format!("{:.0}", 9.4f64));
assert!("10" == format!("{:.0}", 9.9f64));
assert!("9.8" == format!("{:.1}", 9.849f64));
assert!("9.9" == format!("{:.1}", 9.851f64));
assert!("1" == format!("{:.0}", 0.5f64));
fn test_format_f64() {
assert_eq!("1", format!("{:.0}", 1.0f64));
assert_eq!("9", format!("{:.0}", 9.4f64));
assert_eq!("10", format!("{:.0}", 9.9f64));
assert_eq!("9.8", format!("{:.1}", 9.849f64));
assert_eq!("9.9", format!("{:.1}", 9.851f64));
assert_eq!("1", format!("{:.0}", 0.5f64));
assert_eq!("1.23456789e6", format!("{:e}", 1234567.89f64));
assert_eq!("1.23456789e3", format!("{:e}", 1234.56789f64));
assert_eq!("1.23456789E6", format!("{:E}", 1234567.89f64));
assert_eq!("1.23456789E3", format!("{:E}", 1234.56789f64));
}

#[test]
fn test_format_f32() {
assert_eq!("1", format!("{:.0}", 1.0f32));
assert_eq!("9", format!("{:.0}", 9.4f32));
assert_eq!("10", format!("{:.0}", 9.9f32));
assert_eq!("9.8", format!("{:.1}", 9.849f32));
assert_eq!("9.9", format!("{:.1}", 9.851f32));
assert_eq!("1", format!("{:.0}", 0.5f32));
assert_eq!("1.2345679e6", format!("{:e}", 1234567.89f32));
assert_eq!("1.2345679e3", format!("{:e}", 1234.56789f32));
assert_eq!("1.2345679E6", format!("{:E}", 1234567.89f32));
assert_eq!("1.2345679E3", format!("{:E}", 1234.56789f32));
}