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digitalmars.D.bugs - [Issue 9447] New: iota should generate char intervals too

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9447

           Summary: iota should generate char intervals too
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



Spinoff of Issue 8920


import std.range: iota;
void main() {
    foreach (i; iota('a', 'f')) {}
}


DMD 2.062alpha gives:

temp.d(3): Error: template std.range.iota does not match any function template
declaration. Candidates are:
...\dmd2\src\phobos\std\range.d(5107):        std.range.iota(B, E, S)(B begin,
E end, S step) if ((isIntegral!(CommonType!(B, E)) || isPointer!(CommonType!(B,
E))) && isIntegral!(S))
...\dmd2\src\phobos\std\range.d(5192):        std.range.iota(B, E)(B begin, E
end) if (isFloatingPoint!(CommonType!(B, E)))
...\dmd2\src\phobos\std\range.d(5199):        std.range.iota(B, E)(B begin, E
end) if (isIntegral!(CommonType!(B, E)) || isPointer!(CommonType!(B, E)))
...\dmd2\src\phobos\std\range.d(5260):        std.range.iota(E)(E end)
...\dmd2\src\phobos\std\range.d(5267):        std.range.iota(B, E, S)(B begin,
E end, S step) if (isFloatingPoint!(CommonType!(B, E, S)))
temp.d(3):        ... (1 more, -v to show) ...
...\dmd2\src\phobos\std\range.d(5107): Error: template std.range.iota cannot
deduce template function from argument types !()(char,char)

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Feb 03 2013
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9447


Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich gmail.com



10:15:42 PST ---
The reason I mentioned Unicode in Issue 8920 is because I'm unsure whether
simply incrementing the integral value of a character will produce a valid
character (valid in how the Unicode standard defines it). 

For ASCII 'a'--'z' it's likely not an issue, but I'm thinking about the case of
wchars and dchars. E.g. we would probably have to use isValidDchar.

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Feb 04 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jmdavisProg gmx.com



PST ---
It is definitely _not_ the case that adding 1 to a wchar or dchar will
necessarily result in a valid value. In both of them, there's a block in the
middle which is invalid. Just like at the implementation of isValidDchar.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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10:57:34 PST ---


 It is definitely _not_ the case that adding 1 to a wchar or dchar will
 necessarily result in a valid value. In both of them, there's a block in the
 middle which is invalid. Just like at the implementation of isValidDchar.


Is this the only restriction though? If that's so, it should be easy to
implement this feature with a single runtime check to verify the range doesn't
go over the invalid block.

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Feb 04 2013
prev sibling parent d-bugmail puremagic.com writes:
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monarchdodra gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |monarchdodra gmail.com







 It is definitely _not_ the case that adding 1 to a wchar or dchar will
 necessarily result in a valid value. In both of them, there's a block in the
 middle which is invalid. Just like at the implementation of isValidDchar.


 
 Is this the only restriction though? If that's so, it should be easy to
 implement this feature with a single runtime check to verify the range doesn't
 go over the invalid block.


I think that is a bad idea. We should keep it simple: User asks to iterate over
xchars of values low to high, and that is all we should return.

When it comes to wchars or dchars, the notion of "invalid" is really in the eye
of the beholder anyway.

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Jul 26 2013