42 lines
1.8 KiB
Coq
42 lines
1.8 KiB
Coq
From Coq Require Import Strings.String.
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Require Import terms.
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Include Terms.
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Module Subst.
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(* scoped variable substitution in type terms *)
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Fixpoint type_subst (v:string) (n:type_term) (t0:type_term) :=
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match t0 with
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| type_var name => if (eqb v name) then n else t0
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| type_fun t1 t2 => (type_fun (type_subst v n t1) (type_subst v n t2))
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| type_univ x t => if (eqb v x) then t0 else type_univ x (type_subst v n t)
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| type_spec t1 t2 => (type_spec (type_subst v n t1) (type_subst v n t2))
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| type_ladder t1 t2 => (type_ladder (type_subst v n t1) (type_subst v n t2))
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| t => t
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end.
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(* scoped variable substitution, replaces free occurences of v with n in expression e *)
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Fixpoint expr_subst (v:string) (n:expr_term) (e0:expr_term) :=
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match e0 with
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| expr_var name => if (eqb v name) then n else e0
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| expr_ty_abs x e => if (eqb v x) then e0 else expr_ty_abs x (expr_subst v n e)
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| expr_ty_app e t => expr_ty_app (expr_subst v n e) t
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| expr_tm_abs x t e => if (eqb v x) then e0 else expr_tm_abs x t (expr_subst v n e)
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| expr_tm_abs_morph x t e => if (eqb v x) then e0 else expr_tm_abs_morph x t (expr_subst v n e)
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| expr_tm_app e a => expr_tm_app (expr_subst v n e) (expr_subst v n a)
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| expr_let x t a e => expr_let x t (expr_subst v n a) (expr_subst v n e)
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| expr_ascend t e => expr_ascend t (expr_subst v n e)
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| expr_descend t e => expr_descend t (expr_subst v n e)
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end.
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(* replace only type variables in expression *)
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Fixpoint expr_specialize (v:string) (n:type_term) (e0:expr_term) :=
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match e0 with
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| expr_ty_app e t => expr_ty_app (expr_specialize v n e) (type_subst v n t)
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| expr_ascend t e => expr_ascend (type_subst v n t) (expr_specialize v n e)
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| expr_descend t e => expr_descend (type_subst v n t) (expr_specialize v n e)
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| e => e
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end.
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End Subst.
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