Problems with sort

[Craig Black]

The following code gives me this error:
algorithm.d(5159): Error: template instance SortedRange!(Range,less) does 
not match template declaration SortedRange(Range,alias pred = "a < b") if 
(isRandomAccessRange!(Unqual!(Range)))

import std.stdio;
import std.algorithm;

struct Range(T)
{
public:
this(T* front, T* back)
{
 frontPtr = front;
 backPtr = back;
}
T* frontPtr, backPtr;
bool empty() const { return backPtr < frontPtr; }
void popFront() { frontPtr++; }
void popBack() { backPtr--; }
ref T front() { return *frontPtr; }
ref T back() { return *backPtr; }
}

void main()
{
int[] a = [9,8,7,6,5,4,3,2,1,0];
auto r = Range!int(&a[0], &a[9]);
sort(r);
writeln(a);
}

Any clue as to what is going on here?

-Craig