fixed-macro

This library provides fixed!, a proc-macro that allows easily creating fixed-point constants for all of the fixed-point types provided in fixed crate.

[dependencies]
fixed-macro = "1.1"

Compiler support: rustc 1.61+.

Details

• The syntax of the macro is as follows:

  fixed!(<value>: <type>)
  

  where <value> is an integer literal or a float literal, and <type> is either of the form I<i>F<f> or U<i>F<f>, matching one of the type aliases provided in fixed::types. Note in particular that <value> has to be a literal and not an arbitrary arithmetic expression, and that <type> is considered a special identifier, so that it doesn't have to be imported first.

• Create a fixed-point constant which is parsed at compile time (the same syntax for int and float literals is supported as in Rust itself, including underscores and scientific notation):

  use fixed_macro::fixed;
  use fixed::types::U8F8;
  
  let x1 = fixed!(-1.23: I32F32);         // float literal (note, the type is not in scope)
  const X2: U8F8 = fixed!(1.2: U8F8);     // can be used to initialize const values
  let x3 = fixed!(123: U8F8);             // decimal integers work as well
  let x4 = fixed!(0x7B: U8F8);            // and hex/oct/bin integers too
  let x5 = fixed!(1_234.567_890: I32F32); // underscores are ignored, same as in rustc
  let x7 = fixed!(0.12e+01: U8F8);        // scientific notation is also supported
  

• For each type alias from fixed::types, there is a macro with a matching name in fixed_macro::types which you can use without specifying the type name:

  use fixed_macro::types::I16F48;
  
  let a1 = I16F48!(-1.23);
  

  Both the macro and the type can happily coexist in the same scope:

  use fixed::types::I16F48;
  use fixed_macro::types::I16F48;
  
  const B1: I16F48 = I16F48!(1.23e-2);
  

  You can choose to import both under different (or same) user-defined names:

  use fixed::types::{I16F48 as Decimal};
  use fixed_macro::types::{I16F48 as dec};
  
  let c1 = dec!(12_345);
  const C2: Decimal = dec!(-0.123_456);
  

License