function unique( arr ) {
	var v;
	var i;
	var j;

	// Loop through the array, only incrementing a pointer when successive values are different. When a succeeding value is different, move the pointer and set the next value. In the trivial case where all array elements are unique, we incur a slight penalty in resetting the element value for each unique value. In other cases, we simply move a unique value to a new position in the array. The end result is a sorted array with unique values.
	for ( i = 1, j = 0; i < arr.length; i++ ) {
		v = arr[ i ];
		if ( arr[ j ] !== v ) {
			j += 1;
			arr[ j ] = v;
		}
	}
	// Truncate the array:
	arr.length = j+1;

	return arr;
}
Mutates a sorted input array to only contain unique values.

@private
@param {Array} arr - sorted array
@returns {Array} input array