Re: [Caml-list] Non-mutable strings

[Patrick M Doane <patrick@watson.org>]

On Thu, 10 Jan 2002, Xavier Leroy wrote:

> If we were to start again from scratch, I'd consider immutable strings
> seriously.  Having mutable strings is handy when they are used as
> character buffers, e.g. by low-level I/O functions.  But I agree there
> are advantages to distinguish (immutable) strings and (mutable)
> character buffers.

In some situations, I've been able to simply make an immutable replacement
for the String module:

module String = struct
  let length = String.length
  let get = String.get
  let create = String.create
  let copy = String.copy
  let sub = String.sub
  (* .. *)
end

# let s = "foo";;
val s : string = "foo"
# s.[0];;
- : char = 'f'
# s.[0] <- 'g';;
Toplevel input:
# s.[0] <- 'g';;
  ^^^^^^^^^^^^
Unbound value String.set

This only works if all the strings in the current context are immutable
though.

Patrick

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