Function Notation with "|"

Question

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.

See https://en.wikipedia.org/wiki/Restriction_(mathematics) – lhf Sep 29 '18 at 01:59 — lhf, Sep 29 '18 at 01:59

score 2 · Accepted Answer · answered Sep 29 '18 at 01:59

2

It means that the domain of the function, say the domain is the set $D$, is restricted to an smaller set $J \subset D$

answered Sep 29 '18 at 01:59

James

score 1 · Answer 2 · answered Sep 29 '18 at 01:59

1

"$f|_J$" means "$f$ restricted to $J$".

answered Sep 29 '18 at 01:59

lhf

2 Answers2