So, in reviewing Level 1, I am reacquainted with the use of si to mean oui. Funny, but, ok. The lesson illustrates this use with an example of denying a negative affirmation, which I presume is meant to provide some sort of emphasis.
I also dug up another use, which is to answer a negative question. (i.e., Aren't you going?) I'm assuming someone is familiar with this additional usage, and my question is, is it the case that, using si to reply, oui, would eliminate the need to repeat the negative question in the affirmative, as is commonly done in English (i.e., yes, I'm going) - unless, of course, you want to hear, “Yes, what?” If so, it would be brilliant, because negative questions are so lame in the first place.
Also, Et si, to mean I'm afraid it is, as opposed to, and if … . I can't find any other reference to this usage anywhere. Are there many other, um, little-known alternative uses for si in French expressions?