Forget function

[jsuit]

I have some questions about forget.

1. What exactly does forget do?
2. When should you call it?
   2.a When should you call it when you are using a LSTM?
3. If you call forget, should you also call recycle?

Here's a test case:
I have a tensor T of size n (batchsize) x 50, each entry represents the indx to lookup a word. Let this represent a batch of size n with 50 timesteps. If I have a LSTM in my model, do (or should) I call forget after I give my model T. I noticed in the language model example, forget was never called if you were using a LSTM.