lean2/tests/lean/extra/show_goal.lean

25 lines
569 B
Text

import data.nat
open nat algebra
example (a b c d : nat) : a + b = 0 → b = 0 → c + 1 + a = 1 → d = c - 1 → d = 0 :=
begin
intro h₁ h₂,
have aeq0 : a = 0, begin
rewrite h₂ at h₁,
exact h₁
end,
intro h₃ h₄,
have deq0 : d = 0, begin
have ceq : c = 0, begin
rewrite aeq0 at h₃,
rewrite add_zero at h₃,
rewrite add_succ at h₃,
krewrite add_zero at h₃,
injection h₃, exact a_1
end,
rewrite ceq at h₄,
repeat (esimp [sub, pred] at h₄),
exact h₄
end,
exact deq0
end