What does that following notation mean in english?
In this case, J is a set, but I am not sure how the "|" relates the set to the function f.
What does that following notation mean in english?
In this case, J is a set, but I am not sure how the "|" relates the set to the function f.
It means that the domain of the function, say the domain is the set $D$, is restricted to an smaller set $J \subset D$