Module std::fmt

String formatting

The core of the formatting system is the Formattable protocol. Implementing it on custom types allows them to be formatted using the standard string-formatting macros (format, write, ...) and the convenience standard I/O macros (print, println, ...).

Protocols

Structs

Functions

• fn debug<T>(value: T) -> DebugAdapter<T>

  source

  Adapter for printing a debug representation of a value.

  This can print most types without them needing to implment custom formatting. Types can override the default behavior by implementing the DebugFormattable protocol, but this is only recommended for types that e.g. contain untagged unions or normally uninitialized fields.

  Example

  use std::fmt::debug;
  
  struct Point { x: i32, y: i32 }
  
  println!("{}", Point { x: 1, y: 2 }.debug()); // prints 'Point { x: 1, y: 2 }'
  Run this example

• fn hex<T>(val: T) -> NumFormatAdapter<T>

  T: Integer

  source

  Write value as a hexadecimal number

  Example

  use std::fmt::hex;
  
  println!("{}", 42.hex()); // prints '2a'
  Run this example

• fn bin<T>(val: T) -> NumFormatAdapter<T>

  T: Integer

  source

  Write value as a binary number

  Example

  use std::fmt::bin;
  
  println!("{}", 42.bin()); // prints '101010'
  Run this example

• fn oct<T>(val: T) -> NumFormatAdapter<T>

  T: Integer

  source

  Write value as an octal number

  Example

  use std::fmt::oct;
  
  println!("{}", 42.oct()); // prints '52'
  Run this example

• fn zero_pad<T>(val: T, pad: usize) -> NumFormatAdapter<T>

  T: Integer

  source

  Pads number with zeros on the left.

  Example

  use std::fmt::zero_pad;
  
  println!("{}", 42.zero_pad(5)); // prints '00042'
  Run this example

• fn precision<T>(val: T, prec: u16) -> FloatFormatAdapter<T>

  T: FloatingPoint

  source

• fn repeat<T>(inner: T, times: usize) -> RepeatAdapter<T>

  T: Formattable<T>

  source

  Repeats value times times.

  Example

  use std::fmt::repeat;
  
  println!("{}", "ha".repeat(3)); // prints 'hahaha'
  Run this example

• fn pad_with<T>(val: T, len: usize, pad: u8) -> GenericPadAdapter<T>

  T: Formattable<T>

  source

  Pads arbitrary formattable value on the left with a specified character.

  Example

  use std::fmt::pad_with;
  
  println!("{}", "ha".pad_with(5, ' ')); // prints '   ha'
  Run this example

• fn char(val: u8) -> CharAdapter

  source

  Writes a single u8 as a character (byte).

  By default, u8 is written as a number.

  Example

  use std::fmt::char;
  
  println!("{}", 'A'); // prints '65'
  println!("{}", 'A'.char()); // prints 'A'
  Run this example

Types

• type Result = Result<(), Error>

  source

Macros