diff options
Diffstat (limited to 'library/core/src/primitive_docs.rs')
| -rw-r--r-- | library/core/src/primitive_docs.rs | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs index 225a679efd2..ac4e668112b 100644 --- a/library/core/src/primitive_docs.rs +++ b/library/core/src/primitive_docs.rs @@ -977,10 +977,22 @@ mod prim_tuple {} /// like `1.0 / 0.0`. /// - [NaN (not a number)](#associatedconstant.NAN): this value results from /// calculations like `(-1.0).sqrt()`. NaN has some potentially unexpected -/// behavior: it is unequal to any float, including itself! It is also neither -/// smaller nor greater than any float, making it impossible to sort. Lastly, -/// it is considered infectious as almost all calculations where one of the -/// operands is NaN will also result in NaN. +/// behavior: +/// - It is unequal to any float, including itself! This is the reason `f32` +/// doesn't implement the `Eq` trait. +/// - It is also neither smaller nor greater than any float, making it +/// impossible to sort by the default comparison operation, which is the +/// reason `f32` doesn't implement the `Ord` trait. +/// - It is also considered *infectious* as almost all calculations where one +/// of the operands is NaN will also result in NaN. The explanations on this +/// page only explicitly document behavior on NaN operands if this default +/// is deviated from. +/// - Lastly, there are multiple bit patterns that are considered NaN. +/// Rust does not currently guarantee that the bit patterns of NaN are +/// preserved over arithmetic operations, and they are not guaranteed to be +/// portable or even fully deterministic! This means that there may be some +/// surprising results upon inspecting the bit patterns, +/// as the same calculations might produce NaNs with different bit patterns. /// /// For more information on floating point numbers, see [Wikipedia][wikipedia]. /// |