In a program I'd like to perform binary searches on a random access range similar to r4, the result of a sort.group.array:


import std.algorithm: sort, group;
import std.array: array;
void main() {
    auto data = [10, 3, 1, 2, 11, 1, 3, 10];
    auto r1 = sort(data);
    pragma(msg, typeof(r1)); // SortedRange!(int[], "a < b")
    auto r2 = array(r1);
    pragma(msg, typeof(r2)); // int[]
    auto r3 = group(r1);
    pragma(msg, typeof(r3)); // Group!("a == b", SortedRange!(int[], "a < b"))
    auto r4 = array(r3);
    pragma(msg, typeof(r4)); // Tuple!(int, uint)[]
}


In this program r4 is a Tuple!(int,uint)[]. But I'd like r4 to be something like a SortedRange!(int[],"a < b").

To convert r4 to a SortedRange there is the assumeSorted, that performs a bit of tests. But assumeSorted should not be needed because group doesn't break the property of being sorted.

So what I'd like is a function similar to array(), that fed with a lazy Group!SortedRange returns a proper eager SortedRange. Or maybe just an agroup() function that returns an eager SortedRange. Do you have ideas?

Bye,
bearophile

Is this ER going to somehow help?

http://d.puremagic.com/issues/show_bug.cgi?id=9616

Bye,
bearophile