lean2/doc/demo/add_assoc.lean

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import tactic
using Nat
rewrite_set basic
add_rewrite add_zerol add_succl eq_id : basic
theorem add_assoc (a b c : Nat) : a + (b + c) = (a + b) + c
:= induction_on a
(have 0 + (b + c) = (0 + b) + c :
by simp basic)
(λ (n : Nat) (iH : n + (b + c) = (n + b) + c),
have (n + 1) + (b + c) = ((n + 1) + b) + c :
by simp basic)
exit
check add_zerol
check add_succl
check @eq_id
print environment 1