[RFC] replaceInto

[Jonathan M Davis]

On Sunday, March 04, 2012 22:21:46 Timon Gehr wrote:
> On 03/04/2012 09:48 PM, Dmitry Olshansky wrote:
> > This is proposal was dictated by a simple sudden need when designing
> > with ranges in mind. It's to introduce into Phobos the idiomatic
> > function replaceInto taking an output range to store the result in.
> > 
> > The signature revolves around:
> > void replace(..., Sink)(..., Sink sink)
> > if(... && isOutputRange!Sink)
> > 
> > Motivating example (std.array replace):
> > 
> > auto writer = stdout.lockingTextWriter; //or pick an Appender
> > foreach(line; stdin.byLine)
> > writer.put(replace(line, "Nick", "Nicholas"));
> > 
> > 
> > Skiping hardcoded strings, and lockingTextWriter (it has problems) at
> > the very deep level we see - what exactly? A horrible inefficiency, of
> > course! There is no need to allocate space for replaced string and even
> > doing it on buffer in-place risks allocation.
> > 
> > With proposed replaceInto:
> > 
> > auto writer = stdout.lockingTextWriter; //or pick an Appender
> > foreach(line; stdin.byLine)
> > replaceInto(line, "Nick", "Nicholas", writer);
> > 
> > Look ma, no allocations!
> > 
> > Same goes for e.g. std.regex replace, coincidence, coincidence :)
> > 
> > P.S. A DIP 9 flashback?
> 
> Yes, we need this.

I've been considering that we should probably add overloads which take an 
output range to most of the functions in std.string - and possibly a number in 
std.array - so that we can get that extra boost of efficiency, but I haven't 
gotten around to doing anything with that yet.

- Jonathan M Davis