From 2581ac99323ead839964e9b5f2a799cf61fd5bdc Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Sat, 18 May 2024 13:08:31 -0700
Subject: Allow pattern matching in function definitions.

---
 parser.sml | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

(limited to 'parser.sml')

diff --git a/parser.sml b/parser.sml
index 8057873..08cb992 100644
--- a/parser.sml
+++ b/parser.sml
@@ -489,15 +489,20 @@ struct
         then Syntax.DValRec (p, e)
         else Syntax.DVal (p, e))))))
   <|> (reserved "fun" >>
-      bind identifier (fn name =>
-      bind (many1 atpat) (fn args =>
-      reserved "=" >>
-      bind expr (fn body =>
-      const
-        (Syntax.DValRec
-          ( Syntax.PVar name
-          , foldr Syntax.ELambda body args
-          ))))))) st
+      bind
+        (sepBy1
+          (bind identifier (fn name =>
+          bind (many1 atpat) (fn args =>
+          reserved "=" >>
+          bind expr (fn body =>
+          const (name, args, body)))))
+          (reserved "|")) (fn cases =>
+      let val (name, _, _) = hd cases
+      in
+        if not (List.all (fn (n, _, _) => n = name) cases)
+        then raise Fail "clauses do not all have same function name"
+        else const (Syntax.DFun (name, map (fn (_, x, y) => (x, y)) cases))
+      end))) st
 
   val program : Syntax.expr parser = (fn decs => Syntax.ELet (decs, Syntax.EInt 0)) <$> many dec
   fun parse (f : string) : (string, Syntax.expr) Result.either = runParser program f
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