Theorem: N.zero_add (LeanTeaching/TD/TD02_sol.lean)

State before:
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ 0 + a = a
Tactic:
induction a with
| zero =>
  rfl
| succ i hi =>
  rw [add_succ, hi]
State after:
no goals

State before:
case zero
S : Type
image_zero : S
image_succ : N → S → S
n m a b c : N
⊢ 0 + zero = zero
Tactic:
rfl
State after:
no goals

State before:
case succ
S : Type
image_zero : S
image_succ : N → S → S
n m a b c i : N
hi : 0 + i = i
⊢ 0 + succ i = succ i
Tactic:
rw [add_succ, hi]
State after:
no goals