Add GeneralizeVar

1 files changed, 29 insertions, 0 deletions

diff --git a/src/Compilers/GeneralizeVar.v b/src/Compilers/GeneralizeVar.v
new file mode 100644
index 000000000..882d8137b
--- /dev/null
+++ b/src/Compilers/GeneralizeVar.v
@@ -0,0 +1,29 @@
+(** * Generalize [var] in [exprf] *)
+Require Import Coq.PArith.BinPos.
+Require Import Crypto.Compilers.Named.Context.
+Require Import Crypto.Compilers.Named.Syntax.
+Require Import Crypto.Compilers.Named.InterpretToPHOAS.
+Require Import Crypto.Compilers.Named.Compile.
+Require Import Crypto.Compilers.Named.PositiveContext.
+Require Import Crypto.Compilers.Named.PositiveContext.Defaults.
+Require Import Crypto.Compilers.Syntax.
+
+(** N.B. This procedure only works when there are no nested lets,
+    i.e., nothing like [let x := let y := z in w] in the PHOAS syntax
+    tree.  This is a limitation of [compile]. *)
+
+Section language.
+  Context {base_type_code : Type}
+          {op : flat_type base_type_code -> flat_type base_type_code -> Type}
+          (base_type_code_beq : base_type_code -> base_type_code -> bool)
+          (base_type_code_bl_transparent : forall x y, base_type_code_beq x y = true -> x = y)
+          (failb : forall var t, @Syntax.exprf base_type_code op var (Tbase t)).
+
+  Local Notation PContext var := (PositiveContext _ var _ base_type_code_bl_transparent).
+
+  Definition GeneralizeVar {t} (e : @Syntax.expr base_type_code op (fun _ => FMapPositive.PositiveMap.key) t)
+    : option (@Syntax.Expr base_type_code op (domain t -> codomain t))
+    := let e := compile e (default_names_for (fun _ => 1%positive) e) in
+       let e := option_map (InterpToPHOAS (Context:=fun var => PContext var) failb) e in
+       e.
+End language.