David Rajchenbach-Teller <David.Teller@ens-lyon.org> writes:

> On Sat, 2009-04-04 at 19:35 -0400, Yaron Minsky wrote:
>> On Sat, Apr 4, 2009 at 5:51 PM, Goswin von Brederlow
>> <goswin-v-b@web.de> wrote:
>>         Mutable/Immutable can really nicely done with phantom types
>>         and is
>>         independent of the data structure used. It works for strings,
>>         lists,
>>         arrays, sets, trees, ... and I think all standard modules
>>         should have
>>         it. The official standard lib is rather lacking there but that
>>         is why
>>         there is Batteries. The more I hear/see of it the more I like
>>         it.
>> 
>> On this note, there's a small variation on this idea that we've
>> experimented with at Jane Street that I think is worth mentioning.
>> When people do this kind of thing, they usually have two phantom tags,
>> "immutable" and "mutable", but, there is another natural one to add:
>> "readonly".
>
> Actually, thats exactly what we have for strings and arrays in
> Batteries.
>
> Cheers,
>  David

Where do you have an immutable string? One where you are sure that
nobody can hold a [> `Write] reference to the string. I only saw the
read and write phantom flags.

MfG
        Goswin