lean4-htt/tests/lean/run/stateT1.lean

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meta definition mytactic (A : Type) := stateT (list nat) tactic A
attribute [instance]
meta definition mytactic_is_monad : monad mytactic :=
@stateT.monad _ _ _
meta definition read_lst : mytactic (list nat) :=
stateT.read
meta definition write_lst : list nat → mytactic unit :=
stateT.write
meta definition foo : mytactic unit :=
write_lst [10, 20]
meta definition ins (a : nat) : mytactic unit :=
do l : list nat ← read_lst,
write_lst (a :: l)
meta definition invoke (s : list nat) (m : mytactic unit) : tactic (list nat) :=
do (u, s') ← m s, return s'
meta definition tactic_to_mytactic {A : Type} (t : tactic A) : mytactic A :=
λ s, do a : A ← t, return (a, s)
open tactic
example : list nat :=
by do
l : list nat ← invoke [] (foo >> ins 30 >> tactic_to_mytactic (trace "foo") >> ins 40),
trace l,
mk_const `list.nil >>= apply