problem with floor function

[jblindsay]

There appears to be an unexpected behaviour with the floor function for f64 (likely f32 as well). When applied to values greater than -1.0 and less than 0.0, it returns 0.0 instead of -1.0. That is, it is rounding up (ceil) rather than down in this one range of values.

assert_eq!(-0.8f64.floor(), -1f64);

[varkor]

Edit: I entirely misread. See below.

[ollie27]

-0.8f64.floor() is equivalent to -(0.8f64.floor()) not (-0.8f64).floor().

[oli-obk]

Maybe clippy could lint -foo.operation() expressions?

[varkor]

Whoops. I do think the precedence here is confusing. It's easy to think of the minus sign as being part of the literal. A clippy lint would be helpful.

[oli-obk]

Opened rust-lang/rust-clippy#3903