The usage of YET

Guys,

Last class we talked about the possibility of yet show up in a positive sentence.
I found a good explanation about the usage of the word and I would like you to have a look on it. Click here if you want to see the original web site.
yet

Main Entry: yet
Pronunciation: \ˈyet\
Function: adverb
Etymology: Middle English, from Old English gīet; akin to Old Frisian ieta yet
Date: before 12th century

1 a : in addition : besides b : even 2c c : on top of everything else : no less
2 a (1) : up to now : so far —often used to imply the negative of a following infinitive (2) : at this or that time : so soon as now b : continuously up to the present or a specified time : still c : at a future time : eventually
3 : nevertheless, however

— as yet : up to the present or a specified time

— yet again : one more time