rust-lang / rust-lang/rfcs

Implement fmt traits for floating-point types

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Description

Currently f32 and f64 do not implement many of the fmt traits:

  • fmt::Binary: does .to_bits() and prints the integer as binary
  • fmt::Octal: does .to_bits() and prints the integer as octal
  • fmt::LowerHex: equivalent to printf("%a") [0]
  • fmt::UpperHex: equivalent to printf("%A") [0]

That is pretty annoying when working with floating point numbers. Methods that would allow to format independent parts of the representation like the mantissa would also help.

cc @cuviper


[0]: to obtain the hex representaiton of the float as an integer one can just use .to_bits().

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Research direction

Start by reviewing the requested f32 and f64 implementations for fmt::Binary, fmt::Octal, fmt::LowerHex, and fmt::UpperHex, including the stated to_bits() and printf("%a") comparisons. No source file or test is identified; done would require a resolved design and corresponding Rust RFC or implementation scope.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
developer-experience
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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