From 11a51cf708a8a3c38566983fbb0c380a6352312a Mon Sep 17 00:00:00 2001
From: Scott Richmond <kredati@users.noreply.github.com>
Date: Sun, 20 Mar 2022 14:14:15 -0400
Subject: [PATCH] Interpret match expressions

---
 src/ludus/interpreter.clj | 34 ++++++++++++++++++++++++++++++++--
 src/ludus/parser.clj      | 12 ++++++------
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/src/ludus/interpreter.clj b/src/ludus/interpreter.clj
index 245e3cf..f903701 100644
--- a/src/ludus/interpreter.clj
+++ b/src/ludus/interpreter.clj
@@ -97,6 +97,30 @@
       (interpret else-expr ctx)
       )))
 
+(defn- interpret-match [ast ctx]
+  (let [match-expr (:expr ast)
+        expr (interpret match-expr ctx)
+        clauses (:clauses ast)]
+    (loop [clause (first clauses)
+           clauses (rest clauses)]
+      (if clause
+        (let [pattern (:pattern clause)
+              body (:body clause)
+              new-ctx (atom {::parent ctx})
+              match? (match pattern expr new-ctx)
+              success (:success match?)
+              clause-ctx (:ctx match?)]
+          (if success
+            (do 
+              (swap! new-ctx #(merge % clause-ctx))
+              (interpret body new-ctx))
+            (recur (first clauses) (rest clauses))
+            ))
+        (throw (ex-info "Match Error: No match found" {}))
+        ))
+    )
+  )
+
 (defn interpret [ast ctx]
   (case (::ast/type ast)
 
@@ -108,6 +132,8 @@
 
     ::ast/if (interpret-if ast ctx)
 
+    ::ast/match (interpret-match ast ctx)
+
     ::ast/block
     (let [exprs (:exprs ast)
           inner (pop exprs)
@@ -154,8 +180,12 @@
 (do
 
   (def source "
-	let (foo, (_, baz)) = (1, (2, 3))
-	baz
+	let foo = (1, 2)
+	match foo with {
+		0 -> :zero
+		(_, 3) -> :one
+		& baz -> baz
+	}
 ")
 
   (println "")
diff --git a/src/ludus/parser.clj b/src/ludus/parser.clj
index 4857bf5..7e01a5e 100644
--- a/src/ludus/parser.clj
+++ b/src/ludus/parser.clj
@@ -466,7 +466,7 @@
     (let [curr (current parser)]
       (case (::token/type curr)
         ::token/rbrace
-        (assoc parser ::ast {::ast/type ::ast/clauses :clauses clauses})
+        (assoc (advance parser) ::ast {::ast/type ::ast/clauses :clauses clauses})
 
         ::token/newline
         (recur (accept-many #{::token/newline} parser) clauses)
@@ -566,10 +566,10 @@
 (do
   (def pp pp/pprint)
   (def source "match foo with {
-      _ -> foo
-      foo () -> bar
-      () -> baz
-    }")
+    0 -> foo
+  }
+  
+  ")
   (def lexed (scanner/scan source))
   (def tokens (:tokens lexed))
   (def p (parser tokens))
@@ -581,7 +581,7 @@
   (println "*** *** NEW PARSE *** ***")
 
   (-> p
-    (parse-match)
+    (parse-script)
     (::ast)
     (pp)
     )