[phobos] UTF-8 string slicing

unDEFER undefer at gmail.com
Fri Aug 19 03:07:53 PDT 2011

On Fri, 19 Aug 2011 06:53:37 +0400, Jonathan M Davis <jmdavisProg at gmx.com>  

> Hmmm. Such a function isn't entirely a bad idea, but it also makes me a  
> bit
> nervous. Slicing is efficient. The slice function that you suggest is  
> not. I
> mean, it's efficient enough for what it's doing, but it's not O(1) like  
> slicing
> is, so having a slice function could be a bit misleading.

I know that it is not efficient, but here just appears the question why D  
have decided not support 8-but encodings. Only its makes operations  like  
this efficient.

> Once drop has been merged in, you'll be able do to this
> auto s = takeExactly(drop(str, firstIndex), lastIndex - firstIndex));
> to get the same effect. It may be worth adding such a function though.

I'm sorry, but looks like there is no "drop()" function.
Anyway, thank you. I really don't understand how takeExactly works, but it  
works. For newbies it is really not obvious that std.range works fine with  
UTF-8 strings.

> Certainly
> auto s = slice(firstIndex, lastIndex);
> is cleaner. If we add it though, then we should probably give it a  
> different name. Maybe sliceByElementType? That does seem a bit long  
> though, if accurate.

In many other languages this function named as "subString".

> We'd probably put it in std.range though rather than std.utf, since it  
> could
> be useful for any range which isn't actually sliceable. And then there's  
> the
> question of whether it would be better to make it lazy. It would make it  
> so
> that it wasn't actually a string anymore, but it would make it more  
> efficient for all of the cases where you don't actually end up using the  
> whole slice.
> You can make a pull request for it if you want to, and the best way to  
> handle it - as well as whether we actually want such a function - can be  
> discussed in the pull request. I do think that some thought is going to  
> have to go into what behavior we really want such a function to have  
> though (as well as the best name for it).

I'm not familiar with Git, but I'll try to think up anything.

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