[Issue 3384] New: toArray

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3384

           Summary: toArray
           Product: D
           Version: 2.033
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Keywords: patch
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: dsimcha at yahoo.com


--- Comment #0 from David Simcha <dsimcha at yahoo.com> 2009-10-09 10:16:21 PDT ---
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;
    }
}

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