Re: Strange crash on custom iterator

["Dan'l Miller" <optikos@verizon.net>]

On Tuesday, July 3, 2018 at 4:04:54 PM UTC-5, Lucretia wrote:
> On Tuesday, 3 July 2018 21:18:28 UTC+1, Dmitry A. Kazakov  wrote:
> 
> > > Well, they kind of already did that by subtyping UTF_String from String, of which it's not a subtype, it's just they are both arrays of 8-bit entities.
> > 
> > No. Both are arrays of code points and arrays of octets. The ranges of 
> > code points are different. The correspondence between code points and 
> > octets are different. Thus the subtyping is broken.
> 
> I know the difference between code points and octets and their arrays. I was saying that UTF_String is
> not a valid subtype of String because String is Latin 1 and UTF_String is a superset of 7-bit ASCII, not
> 8-bit Latin 1.

Well, there are 2 ways of looking at UTF-8: before versus after parsing.

is not a superset:
One is whether each 8-bit value in Latin-1 has the same value in the UTF-8 octet-by-octet representation •prior• to parsing.  Using this analysis, all of the upper 128 values have a different meaning than in Latin-1.

is a superset:
But the other way of looking at UTF-8 is what character is represented by the multi-byte encoding •after• parsing.  In this view, the lowest 256 values of Unicode/ISO10646 conform to Latin-1 (with some quibbling over whether the mark-parity control codes from 16#80 to 16#9F have precisely the same meaning versus reserved/unencoded at various editions of various standards).

> > > Am i wrong, should I just implement what I need on top of the standard lib and just use the UTF* types in my code? What about unbounded_utf_strings? Just use the normal unbounded_string? It's not like it's going to be checking for it to be correct utf8 is it, but I can't write an iterator for that from outside the rts though.
> > 
> > There is no way to do it right in Ada for now.
> 
> What do you mean exactly????

He means that it needs his extrapolation-of-Steelman-3-3F idea for compile-time tagged types that are not tagged records.