type error: converting input channel to string list

type error: converting input channel to string list

[Lyn A Headley]

hi all,

I can't seem to make sense of this type error.  Sorry to air my
dirty laundry but I was hoping I could get some assistance with this
one, as I am stumped.

the code is merely:

(* turn an input channel into a list of strings *)
let string_list_of_chann chann =
  let rec slof_aux (ch: in_channel) (l: string list) = 
    try
      let readstr = input_line ch in
      slof_aux ch readstr::l
    with End_of_file -> l
  in slof_aux chann []

and the error is:

File "query.ml", line 11, characters 19-155:
This expression has type in_channel -> string list -> string list
but is here used with type in_channel -> string -> string
make: *** [all] Error 2


Is this a problem with relying on an exception to type a function?

thanks,
Lyn

Re: type error: converting input channel to string list

[Pierre Weis]

> let string_list_of_chann chann =
>   let rec slof_aux (ch: in_channel) (l: string list) = 
>     try
>       let readstr = input_line ch in
>       slof_aux ch readstr::l
>     with End_of_file -> l
>   in slof_aux chann []
> 
> and the error is:
> 
> File "query.ml", line 11, characters 19-155:
> This expression has type in_channel -> string list -> string list
> but is here used with type in_channel -> string -> string
> make: *** [all] Error 2
> 
> 
> Is this a problem with relying on an exception to type a function?

No, your problem is just parsing: you should write

 slof_aux ch (readstr::l) instead of slof_aux ch readstr::l

since in Caml, function application binds tighter than operations,
that is, for all binary infix operator op

f x op z means (f x) op z

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/