Prefix operators in ocaml

Prefix operators in ocaml

[Eduardo Gimenez]

Hello,

Which is the "prefix" name in Ocaml for the multiplication on
integers? The symbols (+), (/), etc. work fine for the other
arithmetic operations, but the symbol (*) does not.

Similarly, is there any prefix name for the list constructor (a::l) ?
I am thinking in something like (::) .... 

Of course, I could define a function with the same behavior:
# let cons x y = x::y;;
val cons : 'a -> 'a list -> 'a list = <fun>

but this does not enable to write down expressions like 
match x with cons (a,l) -> l.

PS: I am working in the context of automatic generation of ocaml code,
and being able to have a uniform treatment for datatype constructors
would simplify things a lot....

Thanks in advance,
Eduardo Gimenez.

Prefix operators in ocaml

[William Chesters]

Eduardo Gimenez writes:
 > 
 > Hello,
 > 
 > Which is the "prefix" name in Ocaml for the multiplication on
 > integers? The symbols (+), (/), etc. work fine for the other
 > arithmetic operations, but the symbol (*) does not.

LOL :) :).

It's because (* begins a comment *).
You have to write ( * ).

This is truly disgusting and is on a par with C++'s "idiom"

	List<Array<int> >

 > Similarly, is there any prefix name for the list constructor (a::l) ?
 > I am thinking in something like (::) .... 

Yes, this is an example where following SML/NJ's habit of treating
constructors more uniformly with functions would be advantageous.
Although for all I know there may be implementation reasons not to do
it.

Re: Prefix operators in ocaml

[Chris Keane]

>>>>> On Thu, 21 Jan 1999, "EG" = Eduardo Gimenez wrote:

  EG> Which is the "prefix" name in Ocaml for the multiplication on
  EG> integers? The symbols (+), (/), etc. work fine for the other
  EG> arithmetic operations, but the symbol (*) does not.

I think you're probably just finding that the (* is being treated as the
start of a comment.  Put a space after the first bracket, thus: ( *), and
it should work as you require.

Chris.

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[Jun P. Furuse]

> Which is the "prefix" name in Ocaml for the multiplication on
> integers? The symbols (+), (/), etc. work fine for the other
> arithmetic operations, but the symbol (*) does not.

You need a small trick. Try ( * ) or ( *).
 
> Similarly, is there any prefix name for the list constructor (a::l) ?
> I am thinking in something like (::) .... 

:: is not an infix operator, but an infix constructor. It is handled
specially by the parser. Like the other normal constructors, you
always need its arguments i.e.:

# type 'a option =
    None
  | Some of 'a

# Some;;
The constructor Some expects 1 argument(s),
but is here applied to 0 argument(s)

# fun x -> Some x;;
- : 'a -> 'a option = <fun>

The constructor names themselves are not functions in O'Caml.
 
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