36 lines
609 B
Text
36 lines
609 B
Text
open tactic nat
|
|
|
|
example (a b : nat) : a ≠ b → ¬ a = b :=
|
|
by do
|
|
intros,
|
|
by_contradiction `H,
|
|
trace_state,
|
|
contradiction
|
|
|
|
print "-------"
|
|
|
|
example (a b : nat) : ¬¬ a = b → a = b :=
|
|
by do
|
|
intros,
|
|
by_contradiction `H,
|
|
trace_state,
|
|
contradiction
|
|
|
|
print "-------"
|
|
|
|
example (p q : Prop) : ¬¬ p → p :=
|
|
by do
|
|
intros,
|
|
by_contradiction `H, -- should fail
|
|
trace_state
|
|
|
|
print "-------"
|
|
|
|
local attribute [instance] classical.prop_decidable -- Now all propositions are decidable
|
|
|
|
example (p q : Prop) : ¬¬p → p :=
|
|
by do
|
|
intros,
|
|
by_contradiction `H,
|
|
trace_state,
|
|
contradiction
|