fsharp / fsharp/fsharp-core-docs

Inaccurate/misleading description of max in operators module (wrt. NaN comparison)

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Descrizione

Not sure if this is an error in documentation or purposeful omission, or perhaps a bug in fsharp.

[Here](https://fsharp.github.io/fsharp-core-docs/reference/fsharp-core-operators.html#max) `max` is described as

> Maximum based on generic comparison

And [here](https://fsharp.github.io/fsharp-core-docs/reference/fsharp-core-operators.html#compare) `compare` is described as

> Generic comparison.

However, even though they kind of boil down to the same thing in implementation for most types, they do not specifically for floating point numbers. Moreover, if one defines a max function with `compare`, for example like this:

```fsharp
let max2 x y = if compare x y < 0 then y else x
```

Then `max2` behaves differently than `max` with respect to NaN, e.g.:
```
> max2 1. nan;;
val it: float = 1.0

> max2 nan 1.;;
val it: float = 1.0
```
whereas
```
> max nan 1.;;
val it: float = nan

> max 1. nan;;
val it: float = nan
```

If this discrepancy in behavior is expected, then perhaps it should be documented?

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