pairWise summation for input ranges

pairWise.d

/++
$(LUCKY Pairwise summation) algorithm. Range must be a finite range.
+/
private F sumPairwise(Range, F = Unqual!(ForeachType!Range))(Range data)
if (isInputRange!Range && !isInfinite!Range)
{
    import core.bitop : bsf;
    // Works for r with length < 2^^64, in keeping with the use of size_t
    // elsewhere in std.algorithm and std.range on 64 bit platforms.
    F[64] store = F.max;

    size_t idx = 0;
    foreach (i, el; enumerate(data))
    {
        store[idx] = el;
        foreach (_; 0 .. (i+1).bsf)
        {
            store[idx - 1] += store[idx];
            --idx;
        }
        ++idx;
    }

    F s = store[idx - 1];
    foreach_reverse (i; 0 .. idx - 1)
        s += store[i];

    return s;
}