http://habrahabr.ru/post/91605/

binsearch.d

import std.stdio;

/+
int bins(int[] arr, int what, int left = 0, int right = -1)
{
	if(right == -1) right = cast(int)arr.length;
	int l = left;
	int r = right;
	if(l >= r) return -1;
	int m = (l + r) / 2;
	if(arr[m] == what) return m;
	return arr[m] > what ? bins(arr, what, l, m) : bins(arr, what, m + 1, r);
}
+/
//                                                                         ^ lost this first time

int bins(int[] arr, int what, int skipped = 0)
{
	if(arr.length == 0) return -1;
	int m = cast(int)arr.length / 2;
	if(arr[m] == what) return skipped + m;
	return arr[m] > what ? bins(arr[0 .. m], what, skipped) : bins(arr[m + 1 .. $], what, skipped + m + 1);
}
//                                                                             ^ lost this again, and this  ^

void test(int[] arr)
{
	writeln(arr);
	foreach(i, a; arr) 
	{
		write(a, ' ');
		assert(bins(arr, a) == i);
	}
	writeln();
	writeln("1");
	assert(bins(arr, 5) == -1);
	writeln("2");
	assert(bins(arr, 0) == -1);
	writeln("3");
	assert(bins(arr, 10) == -1);
	writeln("+");
}

unittest
{
	test([]);
	test([1]);
	test([1, 2, 3]);
	test([1, 2, 3, 4]);
	test([1, 2, 3, 4, 6, 7, 8]);
	test([1, 2, 3, 4, 6, 7, 8, 9]);

}

int main() { return 0; }