From 122fd50d4a7fee989bdcf69dc699d7bcf4246600 Mon Sep 17 00:00:00 2001
From: Chris Double <chris@bethia.(none)>
Date: Tue, 1 Apr 2008 14:49:20 +1300
Subject: [PATCH] Throw error when ebnf uses a non-existant non-terminal

---
 extra/peg/ebnf/ebnf.factor | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/extra/peg/ebnf/ebnf.factor b/extra/peg/ebnf/ebnf.factor
index 26e5d68df8..a6567ce8f3 100644
--- a/extra/peg/ebnf/ebnf.factor
+++ b/extra/peg/ebnf/ebnf.factor
@@ -310,9 +310,14 @@ M: ebnf-var (transform) ( ast -- parser )
 M: ebnf-terminal (transform) ( ast -- parser )
   symbol>> token sp ;
 
+: parser-not-found ( name -- * )
+  [
+    "Parser " % % " not found." %
+  ] "" make throw ;
+
 M: ebnf-non-terminal (transform) ( ast -- parser )
   symbol>>  [
-    , parser get , \ at , \ sp ,   
+    , \ dup , parser get , \ at , [ parser-not-found ] , \ unless* , \ sp , \ nip ,   
   ] [ ] make box ;
 
 : transform-ebnf ( string -- object )