Clippy lint · Nursery · checked with Clippy 0.1.99

clippy::while_float: while condition comparing floats

What it meansChecks for while loops comparing floating point values. It is in the nursery group and off by default.

What you see

warning: while condition comparing floats
 --> main.rs:4:7
  |
4 | while x < 42.0 {
  |       ^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#while_float
  = note: `-W clippy::while-float` implied by `-W clippy::nursery`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

If you increment floating point values, errors can compound, so, use integers instead if possible.

New lints still being finished. Off by default and may have false positives.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

let mut x = 0.0;
while x < 42.0 {
    x += 1.0;
}

Write this instead

let mut x = 0;
while x < 42 {
    x += 1;
}

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
while_float = "warn"

In code

#![warn(clippy::while_float)]

One run

cargo clippy -- -W clippy::while-float

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Nurserygroup

allowdefault level

nofixed by cargo clippy --fix

1.80.0added in Rust

Clippy's own documentation

What it does

Checks for while loops comparing floating point values.

Why is this bad?

If you increment floating point values, errors can compound, so, use integers instead if possible.

Known problems

The lint will catch all while loops comparing floating point values without regarding the increment.

Example

let mut x = 0.0;
while x < 42.0 {
    x += 1.0;
}

Use instead:

let mut x = 0;
while x < 42 {
    x += 1;
}

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

Up next

Also worth your time

Did this answer your question?