[m-rev.] for review: Announce recent changes to string type and string module.

[Julien Fischer]

Hi Peter,

On Mon, 18 Nov 2019, Peter Wang wrote:

> NEWS:
>    Announce changes regarding ill-formed code unit sequences in
>    strings.
>
> library/string.m:
>    Delete a note about ongoing work.
>
> diff --git a/NEWS b/NEWS
> index f41c9fb8e..b9f1b132a 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -462,6 +462,12 @@ Changes to the Mercury standard library:
>    - foldr_substring/5
>    - foldr_substring/6
> 
> +* The string type has been defined to permit ill-formed code unit sequences.

I would delete this first sentence; the string type has always been
defined in such a way that ill-formed code unit sequences could occur.
What has actually changed is covered by this next bit.

> +  Predicates and functions in the string module now have defined behaviours
> +  for strings containing ill-formed sequences. Also, some predicates and
> +  functions now have defined behaviour on surrogate code points
> +  (e.g.  failing or throwing an exception) that was previously undefined.
> +
> * The following predicates have been added to the map module:

That's fine otherwise.

Julien.