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    // 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 }

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