Re: [Caml-list] How an exception could be an argument

[Edgar Friendly <thelema314@gmail.com>]

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Here is an example of giving an exception as an argument to a function:

let run_or ~cmd ~err = if Sys.command cmd <> 0 then raise err

and an example usage:

let config_fail = Failure ("Could not configure " ^ p.id)  in
run_or ~cmd:("sh configure" ^ config_opt) ~err:config_fail;

The problem with your code seems to be that you're passing in a result, so
the exception is being raised outside your try...with block.  OCaml's eager
evaluation means that you'll probably have to pass in a function and an
argument (or just a unit function), meaning that your <|||> will be much
uglier:

let (<|||>) (f,x) (g,y) = try f x with Nothing -> g y

((fun () -> raise Nothing), ()) <|||> ((fun str -> str), "ii")

E.

On Fri, Feb 17, 2012 at 1:16 PM, Pierre-Alexandre Voye <ontologiae@gmail.com
> wrote:

> Hello, I'm trying to implement a scala concept "partial application" in
> which one can chains pattern matching function. If the first failed, the
> second is tried.
> It seems it is impossible to give an exception as argument to a function.
>
>
>
> exception Nothing;;
>
> let (<|||>) a b = try a
> with
>
>   | Nothing ->  (try b
> with
>
>                    | Nothing -> raise
> Nothing);;
>
> val ( <|||> ) : 'a -> 'a -> 'a = <fun>
>
>

>
> (raise Nothing) <|||>
> "jj";;
>
> Exception: Nothing.
>
>
> But if I try :
> try (raise Nothing)
> with
>
>   | Nothing ->  (try
> "jj"with
>
>                    | Nothing -> raise
> Nothing);;
>
> - : string = "jj"
>
> Is there a workaround ?
>
>
> Regards,
> P-A
> --
> ---------------------
> https://twitter.com/#!/ontologiae/
> http://linuxfr.org/users/montaigne
>
>

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