63 lines
2.5 KiB
Text
63 lines
2.5 KiB
Text
/-
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Copyright (c) 2016 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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prelude
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import init.meta.tactic init.function
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namespace tactic
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private meta_definition get_constructors_for (e : expr) : tactic (list name) :=
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do env ← get_env,
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I ← return $ expr.const_name (expr.get_app_fn e),
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when (environment.is_inductive env I = ff) (fail "constructor tactic failed, target is not an inductive datatype"),
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return $ environment.constructors_of env I
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private meta_definition try_constructors : list name → tactic unit
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| [] := fail "constructor tactic failed, none of the constructors is applicable"
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| (c::cs) := (mk_const c >>= apply) <|> try_constructors cs
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meta_definition constructor : tactic unit :=
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target >>= get_constructors_for >>= try_constructors
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meta_definition left : tactic unit :=
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do tgt ← target,
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[c₁, c₂] ← get_constructors_for tgt | fail "left tactic failed, target is not an inductive datatype with two constructors",
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mk_const c₁ >>= apply
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meta_definition right : tactic unit :=
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do tgt ← target,
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[c₁, c₂] ← get_constructors_for tgt | fail "left tactic failed, target is not an inductive datatype with two constructors",
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mk_const c₂ >>= apply
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meta_definition constructor_idx (idx : nat) : tactic unit :=
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do cs ← target >>= get_constructors_for,
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some c ← return $ list.nth cs (idx - 1) | fail "constructor_idx tactic failed, target is an inductive datatype, but it does not have sufficient constructors",
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mk_const c >>= apply
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meta_definition split : tactic unit :=
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do [c] ← target >>= get_constructors_for | fail "split tactic failed, target is not an inductive datatype with only one constructor",
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mk_const c >>= apply
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open expr
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private meta_definition apply_num_metavars : expr → expr → nat → tactic expr
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| f ftype 0 := return f
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| f ftype (n+1) := do
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pi m bi d b ← whnf ftype | failed,
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a ← mk_meta_var d,
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new_f ← return $ expr.app f a,
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new_ftype ← return $ expr.instantiate_var b a,
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apply_num_metavars new_f new_ftype n
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meta_definition existsi (e : expr) : tactic unit :=
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do [c] ← target >>= get_constructors_for | fail "existsi tactic failed, target is not an inductive datatype with only one constructor",
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fn ← mk_const c,
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fn_type ← infer_type fn,
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n ← get_arity fn,
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when (n < 2) (fail "existsi tactic failed, constructor must have at least two arguments"),
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t ← apply_num_metavars fn fn_type (n - 2),
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apply (app t e)
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end tactic
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