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Description: Define a function (mapping) with domain and codomain. Definition 6.15(3) of TakeutiZaring p. 27. F : A --> B can be read as " F is a function from A to B ". For alternate definitions, see dff2 , dff3 , and dff4 . (Contributed by NM, 1-Aug-1994)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | df-f | |- ( F : A --> B <-> ( F Fn A /\ ran F C_ B ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 0 | cF | |- F |
|
| 1 | cA | |- A |
|
| 2 | cB | |- B |
|
| 3 | 1 2 0 | wf | |- F : A --> B |
| 4 | 0 1 | wfn | |- F Fn A |
| 5 | 0 | crn | |- ran F |
| 6 | 5 2 | wss | |- ran F C_ B |
| 7 | 4 6 | wa | |- ( F Fn A /\ ran F C_ B ) |
| 8 | 3 7 | wb | |- ( F : A --> B <-> ( F Fn A /\ ran F C_ B ) ) |