lean2/tests/lean/j6.lean
Leonardo de Moura e9dada5e14 refactor(builtin/kernel): use standard definition for 'or' and 'and'
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2014-02-17 12:05:34 -08:00

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theorem symm_iff (p q : Bool) (H : p ↔ q) : (q ↔ p)
:= symm H
theorem or_imp2 (p q : Bool) : (p q) ↔ (¬ p → q)
:= let H1 := symm_iff _ _ (imp_or (¬ p) q) in
let H2 := not_not_eq p in
let H3 := subst H1 H2 in
H3