Re: [Caml-list] Ocaml optimizer pitfalls & work-arounds

["Frédéric Bour" <frederic.bour@lakaban.net>]

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Le 19 janv. 2017 à 12:39, Gabriel Scherer <gabriel.scherer@gmail.com> a écrit :
> 
>> the min, max issues can be avoided without much trouble by using
>> specialized comparison, as provided in standard library extensions.
> 
> Note that min/max are already optimized from generic to specialized
> when the type information is known at type-checking time. (It used to
> be the case that only fully applied calls were optimized, this was
> improved by Frédéric Bour to extend to non-applied primitives in 4.03
> (eg. "let eq : int -> int -> _ = (=)"). That does not work when those
> functions are used inside a functor body at an abstract type (which is
> when we want inlining and specialization to interact better), but
> there neither do Float.equal or Int.compare.

Alas, min/max cannot benefit from this optimisation.

In Pervasives, they are defined as:

let min x y = if x <= y then x else y
let max x y = if x >= y then x else y

Specialization only happens for primitives, here it is a plain definition.
So no specialization unless the definitions are copied and annotated :(.

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