What does the symbol ‹[·]› mean in signal and communication systems?

[j_penac13]

Hello there! I am in a class of signal and communication systems and found this symbol:
‹[·]› But I can't figure what it means, teacher told us to research it. Been reading books like crazy and can't find anything. Hope you can help me.

I put a picture of how he used it, if that helps you.

 

[fourier jr]

looks kind of like a Fourier transform of [.]

 

[j_penac13]

Well, the problem isn't the whole operation, because it is kinda Fourier transform. Thing is what does [.] mean?!

 

[Office_Shredder]

Sometimes authors will use a dot to denote where the thing to be operated is supposed to go. For example, the inner product is linear in the first term can be written as:
< . ,u> is linear for any fixed u. Maybe something similar to that? Not sure about the brackets

 

[fourier jr]

the average value of a function f is usually written as \frac{1}{b-a} \int_{a}^{b}{f(x)dx}

so set a = -T/2 & b = T/2 & then T--> infinity... that's more like it