question on exceptions

question on exceptions

[Julien Verlaguet]

I have the following peace of code

exception E;;
let x=E;;
exception E;;

I don't understand why the two following things are not equivalent :

# x=E;;
- : bool = true

# match x with
   | E -> true
   | _ -> false;;
- : bool = false

Is this normal ?

J

Re: [Caml-list] question on exceptions

[Johann Spies]

On Fri, May 13, 2005 at 03:34:22PM +0200, Julien Verlaguet wrote:
> I have the following peace of code
> 
> exception E;;
> let x=E;;
> exception E;;
> 
> I don't understand why the two following things are not equivalent :
> 
> # x=E;;
> - : bool = true
> 
> # match x with
>   | E -> true
>   | _ -> false;;
> - : bool = false
> 
> Is this normal ?

Maybe.  I am no expert but I suspect the second "exception E;;" causes
the behaviour that you saw.  Look at this:

# exception E;;
let x=E;;
exception E;;
exception E
# val x : exn = E
# exception E
#  x=E;;
- : bool = true
#  match x with
  | E -> true
  | _ -> false;;
    - : bool = false

So far it is the same, but

# exception E;;
exception E
# let x=E;;
val x : exn = E
#  x=E;;
- : bool = true
#  match x with
  | E -> true
  | _ -> false;;
    - : bool = true

Regards
Johann
-- 
Johann Spies          Telefoon: 021-808 4036
Informasietegnologie, Universiteit van Stellenbosch

     "In my Father's house are many mansions: if it were not
      so, I would have told you. I go to prepare a place for
      you. And if I go and prepare a place for you, I will 
      come again, and receive you unto myself; that where I 
      am, there ye may be also."        John 14:2,3