LRUCache.prototype.shift not working properly

[Valentin Hilbig]

LRUCache.prototype.shift() did not work correctly for me. So I hacked it to call .remove, and now it works, as long as only unique keys are in the LRU.

See hilbix@a502469

Not sending a pull-request as this probably is not the right fix, as a core function like .shift() cannot depend on optional function like .remove().

Problems with .shift(), at least:

• It forgets to update the .size.
• And it does not handle .tail

[Valentin Hilbig]

Another note why this is not the correct fix:

The LRU is able to keep several identical values. So following tests must not fail:

var c = new LRUCache(4);

c.put(0,1);
c.put(0,2);
c.put(0,3);
c.put(0,4);

assert.equal(c.size, 4);
assert.deepEqual(c.shift(), {key:0, value:4});
assert.deepEqual(c.shift(), {key:0, value:3});
assert.deepEqual(c.shift(), {key:0, value:2});
assert.deepEqual(c.shift(), {key:0, value:1});
assert.equal(c.size, 0); // check .size correct
c.forEach(function(){assert(false)}, undefined, true);  // check .tail correct

(Note: Not tested, just typed here for clarity.)