From c746f937705e7859506b6658379e3a561f21fde3 Mon Sep 17 00:00:00 2001
From: Rob Rix <robrix@github.com>
Date: Tue, 19 Mar 2024 14:45:20 -0400
Subject: [PATCH] Mendler-style recursion.

---
 semantic-analysis/src/Analysis/Syntax.hs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/semantic-analysis/src/Analysis/Syntax.hs b/semantic-analysis/src/Analysis/Syntax.hs
index d2c4624aa2..2fb0112f90 100644
--- a/semantic-analysis/src/Analysis/Syntax.hs
+++ b/semantic-analysis/src/Analysis/Syntax.hs
@@ -1,10 +1,12 @@
 {-# LANGUAGE QuantifiedConstraints #-}
+{-# LANGUAGE RankNTypes #-}
 module Analysis.Syntax
 ( -- * Syntax
   Term(..)
 , subterms
 , foldTerm
 , paraTerm
+, mendlerTerm
 ) where
 
 import qualified Data.Set as Set
@@ -42,3 +44,9 @@ paraTerm var sig = go
   where
   go (Var v)  = var v
   go (Term s) = sig ((,) <*> go <$> s)
+
+mendlerTerm :: (v -> r) -> (forall r' . (r' -> r) -> sig r'-> r) -> (Term sig v -> r)
+mendlerTerm var sig = go
+  where
+  go (Var v)  = var v
+  go (Term s) = sig go s