[m-rev.] for review: escape all control characters in io.write, deconstruct.functor

[Peter Wang]

On Fri, 15 Jun 2018 18:02:56 +1000 (AEST), Julien Fischer <jfischer at opturion.com> wrote:
> 
> For review by anyone.
> 
> I'll update the NEWS file seprately.
> 
> ----------------------------------------------------
> 
> Escape all control characters in io.write, deconstruct.functor etc.
> 
> The above predicates currently escape all of the C0 control characters (+
> Delete).  This change modifies them to escape all of the characters in the
> Unicode category `Other,control' using backslash escapes when they exist and
> octal escapes otherwise.

Can we switch to hexadecimal escapes (later), seeing as the behaviour
wasn't documented?

> diff --git a/library/term_io.m b/library/term_io.m
> index eeaef88..2f4e627 100644
> --- a/library/term_io.m
> +++ b/library/term_io.m
> @@ -785,7 +785,7 @@ string_is_escaped_char(Char::out, String::in) :-
>   is_mercury_source_char(Char) :-
>       ( char.is_alnum(Char)
>       ; is_mercury_punctuation_char(Char)
> -    ; char.to_int(Char) >= 0x80
> +    ; char.to_int(Char) >= 0xA0  % 0x7f - 0x9f are control characters.
>       ).

Ok.

> 
>   %---------------------------------------------------------------------------%
> @@ -942,39 +942,43 @@ mercury_escape_char(Char) = EscapeCode :-
>       % Note: the code here is similar to code in runtime/mercury_trace_base.c;
>       % any changes here may require similar changes there.
> 
> +% Codepoints: 0x20 -> 0x2f.

I suggest:

    % Codepoints in 0x20..0x2f
    ...
    % Codepoints in 0x30..0x3f
    ...

Otherwise, it looks fine.

Peter