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Mirrors > Home > ILE Home > Th. List > df-case | Unicode version |
Description: The "case" construction: if and are functions, then case ⊔ is the natural function obtained by a definition by cases, hence the name. It is the unique function whose existence is asserted by the universal property of disjoint unions updjud 6967. The definition is adapted to make sense also for binary relations (where the universal property also holds). (Contributed by MC and BJ, 10-Jul-2022.) |
Ref | Expression |
---|---|
df-case | case inl inr |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cR | . . 3 | |
2 | cS | . . 3 | |
3 | 1, 2 | cdjucase 6968 | . 2 case |
4 | cinl 6930 | . . . . 5 inl | |
5 | 4 | ccnv 4538 | . . . 4 inl |
6 | 1, 5 | ccom 4543 | . . 3 inl |
7 | cinr 6931 | . . . . 5 inr | |
8 | 7 | ccnv 4538 | . . . 4 inr |
9 | 2, 8 | ccom 4543 | . . 3 inr |
10 | 6, 9 | cun 3069 | . 2 inl inr |
11 | 3, 10 | wceq 1331 | 1 case inl inr |
Colors of variables: wff set class |
This definition is referenced by: casefun 6970 casedm 6971 caserel 6972 caseinj 6974 caseinl 6976 caseinr 6977 |
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