Pervasives.compare != Pervasives.compare

Pervasives.compare != Pervasives.compare

[Elnatan Reisner]

I was surprised when I noticed the following behavior:

         Objective Caml version 3.11.2

# compare == compare;;
- : bool = false
# let f = compare;;
val f : 'a -> 'a -> int = <fun>
# f == compare;;
- : bool = false
# f == f;;
- : bool = true
# let g = compare;;
val g : 'a -> 'a -> int = <fun>
# f == g;;
- : bool = false

Playing around a bit more, I seemed to find that every time you access  
an 'external' function, you get a distinct reference (is there a  
better term?) to it. This seems a bit odd to me. Can someone explain?

Thanks,

Elnatan

Re: [Caml-list] Pervasives.compare != Pervasives.compare

[Stéphane Glondu]

Le 12/11/2010 06:57, Elnatan Reisner a écrit :
> Playing around a bit more, I seemed to find that every time you access
> an 'external' function, you get a distinct reference (is there a better
> term?) to it. This seems a bit odd to me. Can someone explain?

Think of externals as constructors: they are always fully applied 
internally. So when you partially apply one (or use it with no 
arguments), the compiler eta-expands it and generates a closure that 
eats the remaining arguments and call the external.

You can use the -dinstr (in bytecode) or -S (in native code) 
command-line switch to see how things are actually compiled.


Cheers,

-- 
Stéphane