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| author | kennytm <kennytm@gmail.com> | 2017-11-28 03:16:50 +0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2017-11-28 03:16:50 +0800 |
| commit | 83a6f38556143f790372a666feed50ce3e72957d (patch) | |
| tree | e8567427e31b0183586951308b1f19f1de337ea1 | |
| parent | 8dd10e62ccf44f9542261060147177918afd6611 (diff) | |
| parent | a326d8d1ba6286b1641b8c89d5ae1383fbfac76a (diff) | |
Rollup merge of #46285 - SimonSapin:twos-complement, r=GuillaumeGomez
Document non-obvious behavior of fmt::UpperHex & co for negative integers Before stabilization I’d have suggested changing the behavior, but that time is past.
| -rw-r--r-- | src/libcore/fmt/mod.rs | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs index 660cd0d6dd1..551aa929ce4 100644 --- a/src/libcore/fmt/mod.rs +++ b/src/libcore/fmt/mod.rs @@ -624,6 +624,9 @@ pub trait Display { /// /// The `Octal` trait should format its output as a number in base-8. /// +/// For primitive signed integers (`i8` to `i128`, and `isize`), +/// negative values are formatted as the two’s complement representation. +/// /// The alternate flag, `#`, adds a `0o` in front of the output. /// /// For more information on formatters, see [the module-level documentation][module]. @@ -639,6 +642,8 @@ pub trait Display { /// /// assert_eq!(format!("{:o}", x), "52"); /// assert_eq!(format!("{:#o}", x), "0o52"); +/// +/// assert_eq!(format!("{:o}", -16), "37777777760"); /// ``` /// /// Implementing `Octal` on a type: @@ -671,6 +676,9 @@ pub trait Octal { /// /// The `Binary` trait should format its output as a number in binary. /// +/// For primitive signed integers (`i8` to `i128`, and `isize`), +/// negative values are formatted as the two’s complement representation. +/// /// The alternate flag, `#`, adds a `0b` in front of the output. /// /// For more information on formatters, see [the module-level documentation][module]. @@ -686,6 +694,8 @@ pub trait Octal { /// /// assert_eq!(format!("{:b}", x), "101010"); /// assert_eq!(format!("{:#b}", x), "0b101010"); +/// +/// assert_eq!(format!("{:b}", -16), "11111111111111111111111111110000"); /// ``` /// /// Implementing `Binary` on a type: @@ -719,6 +729,9 @@ pub trait Binary { /// The `LowerHex` trait should format its output as a number in hexadecimal, with `a` through `f` /// in lower case. /// +/// For primitive signed integers (`i8` to `i128`, and `isize`), +/// negative values are formatted as the two’s complement representation. +/// /// The alternate flag, `#`, adds a `0x` in front of the output. /// /// For more information on formatters, see [the module-level documentation][module]. @@ -734,6 +747,8 @@ pub trait Binary { /// /// assert_eq!(format!("{:x}", x), "2a"); /// assert_eq!(format!("{:#x}", x), "0x2a"); +/// +/// assert_eq!(format!("{:x}", -16), "fffffff0"); /// ``` /// /// Implementing `LowerHex` on a type: @@ -767,6 +782,9 @@ pub trait LowerHex { /// The `UpperHex` trait should format its output as a number in hexadecimal, with `A` through `F` /// in upper case. /// +/// For primitive signed integers (`i8` to `i128`, and `isize`), +/// negative values are formatted as the two’s complement representation. +/// /// The alternate flag, `#`, adds a `0x` in front of the output. /// /// For more information on formatters, see [the module-level documentation][module]. @@ -782,6 +800,8 @@ pub trait LowerHex { /// /// assert_eq!(format!("{:X}", x), "2A"); /// assert_eq!(format!("{:#X}", x), "0x2A"); +/// +/// assert_eq!(format!("{:X}", -16), "FFFFFFF0"); /// ``` /// /// Implementing `UpperHex` on a type: |