Phobos needs an easy, efficient way of converting an arbitrary finite range into an array, for example to allow for eager evaluation. Below is a proposed solution. It relies on the existence of newVoid(). (See Bugzilla 3383.)
/**Converts any range to an array on the GC heap by the most efficient means
* available. If it is already an array, duplicates the range.*/
Unqual!(ElementType!(T))[] toArray(T)(T range) if(isInputRange!(T)) {
static if(isArray!(T)) {
// Allow fast copying by assuming that the input is an array.
return range.dup;
} else static if(hasLength!(T)) {
// Preallocate array, then copy.
auto ret = newVoid!(Unqual!(ElementType!(T)))(range.length);
static if(is(typeof(ret[] = range[]))) {
ret[] = range[];
} else {
size_t pos = 0;
foreach(elem; range) {
ret[pos++] = elem;
}
}
return ret;
} else {
// Don't have length, have to use appending.
Unqual!(ElementType!(T))[] ret;
auto app = appender(&ret);
foreach(elem; range) {
app.put(elem);
}
return ret;
}
}
Comment #1 by dsimcha — 2009-11-19T19:43:42Z
I was looking through std.array for unrelated reasons and noticed that there is an array() function already in there. I have no idea when that was added, but it solves this bug.