Searching string for character in binary search

[Joel via Digitalmars-d-learn]

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;
}