Re: Usage of \ in Ada

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Thu, 24 Aug 2006 10:37:21 +0200, Jean-Pierre Rosen wrote:

> Adam Beneschan a �crit :
>> It's probably to prevent stupid errors.  If you have a string literal
>> with an LF in it, it's far more likely (using a fairly traditional
>> representation of the source) that you've forgotten a closing quote
>> than that you intended to put a linefeed in the literal.  And if the
>> language did try to allow a line separator in a string literal (even if
>> it were represented as something like \n in the representation)
> 
> And of course, if you really need an LF in a character string, just use 
> Ada.Characters.Latin_1.LF ....

Sure, but that is not the point. The problem is which code positions are
illegal (non-graphic_character). Consider it from the position of the
designer of a compiler/parser/scanner. (That was the OP question all about)
The same question arises for the designer of an automated code generator
tool. Which encoding-legal code positions can be safely put into string
literals?

ARM 2.1(17) reads "Every code position of ISO 10646 BMP that is not
reserved for a control function is defined to be a graphic_character by
this International Standard. This includes all code positions other than
0000 - 001F, 007F - 009F, and FFFE - FFFF."

I am not a native English speaker, so it is difficult to me to decipher the
above.

Let S be the set of code positions 0..1F U 7F..9F U FFFE..FFFF.

My question to language lawyers is about the relation between S and
graphic_character:

1. Can some x of S be graphic_character?
      (do S and graphic_character intersect)

2. Is any y outside S graphic_character?
      (is complement of S a subset of graphic_character)

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de