8 lines
201 B
Text
8 lines
201 B
Text
import logic
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open tactic
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theorem tst {A : Type} {f : A → A → A} {a b c : A} (H1 : a = b) (H2 : b = c) : f a b = f b c
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:= by apply congr;
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apply (subst H2);
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apply refl;
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assumption
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