Searching string for character in binary search

[Joel]

The number tests work, but not the string one.

void main() {
	assert([1,2,3,4,5,6,7,8,9,10,11].binarySearch(6));
assert(! [1,2,3,4,5,7,8,9,10,11].binarySearch(6));
assert("abcdefghijklmnopqrstuvwxyz".binarySearch('j')); // not 
work
	import std.stdio;
	writeln("Assert tests passed!");
}

bool binarySearch(T)(T[] arr, T n) {
	while(arr.length) {
		auto i = arr.length/2;
		if (arr[i] == n)
			return true;
		else
			if (arr[i]  > n)
				arr = arr[i + 1 .. $];
			else
				arr = arr[0 .. i];
	}
	return false;
}