From 03eb5c1228ea9f5997fc19f7075a90cca1d29820 Mon Sep 17 00:00:00 2001
From: Erik Oosting
Date: Mon, 18 Dec 2023 18:58:35 +0100
Subject: add free variable searching

---
 haskell/app/Lift.hs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 haskell/app/Lift.hs

(limited to 'haskell/app/Lift.hs')

diff --git a/haskell/app/Lift.hs b/haskell/app/Lift.hs
new file mode 100644
index 0000000..12f9bc6
--- /dev/null
+++ b/haskell/app/Lift.hs
@@ -0,0 +1,26 @@
+module Lift where
+
+import Data.Functor.Foldable
+import Data.List
+import Types
+
+converge f a = let a' = f a in if a' == a then a else converge f a'
+
+-- | R-Algebra to move external variables to arguments
+liftArgs :: AExpF (AExp, ([String], AExp)) -> ([String], AExp)
+liftArgs = undefined -- paramorphism
+
+-- | F-Algebras to find free variables
+findVars :: CExpF [String] -> [String]
+findVars (LetF ident fc rest) = converge (\\ [ident]) $ rest ++ (cata findVarsFC fc)
+findVars (IfF cond t e) = t ++ e ++ (cata findVarsAExp cond)
+findVars (FCF fc) = cata findVarsFC fc
+
+findVarsFC :: FuncallF [String] -> [String]
+findVarsFC (AtomF aexp) = cata findVarsAExp aexp
+findVarsFC (CallF id args) = id : (args >>= cata findVarsAExp)
+
+findVarsAExp :: AExpF [String] -> [String]
+findVarsAExp (IdentF ns) = [ns]
+findVarsAExp (LamF args cexp) = converge (\\ args) (fold findVars cexp)
+findVarsAExp def = foldMap id def
-- 
cgit 1.4.1-2-gfad0