[phobos] UTF-8 string slicing

unDEFER undefer at gmail.com
Sat Aug 20 17:54:00 PDT 2011

Thank you again, Jonathan. So "have no length property" means  
std.range.hasLength = false. Now I understand.

On Sun, 21 Aug 2011 03:51:05 +0400, Jonathan M Davis <jmdavisProg at gmx.com>  

> On Saturday, August 20, 2011 13:11:44 unDEFER wrote:
>> Big thanks, Jonathan!
>> You give me very clearly explanations.
>> But what you mean by "strings of char and wchar ... have no length
>> property" if "string.length" really works? Is it a bug?
> All arrays have a length property. It returns the number of elements in  
> the
> array. The issue is std.range.hasLength, which is what is used with  
> range- based functions in template constraints and static ifs. hasLength  
> is true for all arrays _except_ for arrays of char and wchar. This is  
> because strings are ranges of dchar - of code points - whereas they are  
> arrays of code units, and in UTF-8 and UTF-16, there can be more than  
> one code unit per code point. In the general case, calling length on an  
> array of char or wchar isn't going to give you the the number of code  
> points in the array. So, it's normally
> incorrect to use length with arrays of char and wchar in range-based
> functions.
> - Jonathan M Davis
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Nikolay Krivchenkov aka unDEFER
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