CODEWITHSUNDEEP
ocaml
Charlie-Greenman
Charlie-Greenman

Reputation: 1669

How to alter text using OCaml Containers.CCIO

In the ocaml-containers documentation, it gives a great example, how to read in a file, and write the content to a different file here. However, I am trying to see what it would take to modify the text before it is passed from the file being read to file being written. 

let read_filename = "example.ts"
let filename = "example2.ts"

let () =
  let modify_file ~chunks = 
    let r =  Str.regexp "text \\([A-Za-z]+\\)" in
    Str.replace_first r "\\1" chunks in

  CCIO.(
    with_in read_filename
      (fun ic ->
         let chunks = read_chunks ic in
         let new_chunks = modify_file chunks in
         with_out ~flags:[Open_binary] ~mode:0o644 filename
           (fun oc ->
              write_gen oc new_chunks
           )
      )
  )

The issue with this code, is that the compiler complains: 

File "component.ml", line 13, characters 39-45:
Error: This expression has type string gen = unit -> string option
       but an expression was expected of type string

I am trying to figure out what I am doing wrong, but to no avail. Any help would be more than appreciated. Also, suggestions as to the ideal enterprise software to use in OCaml to modify text in files, is more than appreciated. Thank you.

Upvotes: 0

Views: 79

Answers (2)

Et7f3XIV
Et7f3XIV

Reputation: 629

You have a typing problem read_chunk ic return a string gen value

from here we learn that is a function that take unit value () and return a string.

let () =
  CCIO.(
    let modify_file ~chunks = 
      let r =  Str.regexp "example \\([A-Za-z]+\\)" in
      match chunks () with
        None -> chunks (* is the same as (fun () -> None) *)
      | Some chunks ->
        let chunks = Str.replace_first r "\\1" chunks in (* compute once *)
        (fun () -> Some chunks) in
    with_in read_filename
      (fun ic ->
         let chunks = read_chunks ic in
         let new_chunks = modify_file ~chunks in
         with_out ~flags:[Open_binary] ~mode:0o644 filename
           (fun oc ->
              write_gen oc new_chunks
           )
      )
  )

EDIT: explain the error and the change

EDIT 2: I have modifier modify_file so it return antoher string gen and corrected the syntax error: when you use labeled argument you need to add a tilde when calling it

Upvotes: 1

Et7f3XIV
Et7f3XIV

Reputation: 629

What is the type of modify_file. I don't see it in the manual. You should try to add unit value () this way

let new_chunks = modify_file chunks () in and new_chunks will be of type string option You can pattern match as option type.

EDIT:

I have seen that third parameter has type string gen You should modify the 16th line this way: write_gen oc (fun () -> new_chunks)

Upvotes: 0

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