On Sunday, 27 October 2013 at 00:18:41 UTC, Timothee Cour wrote:

I've posted a while back a string=>string substring function that doesn't
allocating: google
"nonallocating unicode string manipulations"

code:

auto slice(T)(T a,size_t u, size_t v)if(is(T==string)){//TODO:generalize to
isSomeString
import std.exception;
auto m=a.length;
size_t i;
enforce(u<=v);
import std.utf;
while(u-- && i<m){
auto si=stride(a,i);
i+=si;
v--;
}
// assert(u==-1);
// enforce(u==-1);
size_t i2=i;
while(v-- && i2<m){
auto si=stride(a,i2);
i2+=si;
}
// assert(v==-1);
enforce(v==-1);
return a[i..i2];
}
unittest{
import std.range;
auto a="≈açç√ef";
auto b=a.slice(2,6);
assert(a.slice(2,6)=="çç√e");
assert(a.slice(2,6).ptr==a.slice(2,3).ptr);
assert(a.slice(0,a.walkLength) is a);
import std.exception;
assertThrown(a.slice(2,8));
assertThrown(a.slice(2,1));
}

Another one, with negative index like Javascript's String.slice():
http://dpaste.dzfl.pl/608435c5