On 05.03.2012 9:43, Jonathan M Davis wrote:
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.
Yes, by the looks of it there is plenty of places to apply this. One
thing that I'm unclear on is should it be overloads?
The problem is that e.g. the fact that replace either returns new array
or nothing depending on the arguments is kind of unexpected for the
reader. Not to mention that overload space was pretty crumbled, that's
why I ended up with replaceInto name.
--
Dmitry Olshansky
