Make left recursion in pegs a failed parse

Eventually left recursion will work fine, but this is prevents an infinite loop for now.

extra/peg/peg-tests.factor

@@ -175,6 +175,8 @@ IN: peg.tests
       [ "1" token , "+" token , "1" token , ] seq* ,
     ] choice* 
     "1-1" over parse parse-result-ast swap
-    "1+1" swap parse parse-result-ast
   ] with-packrat
+  [
+    "1+1" swap parse parse-result-ast
+  ] with-packrat 
 ] unit-test

extra/peg/peg.factor

@@ -34,12 +34,12 @@ GENERIC: (compile) ( parser -- quot )
   #! that maps the input string position to the parser result.
   [ drop H{ } clone ] cache ;
 
-: cached-result ( n input-cache input quot -- result )
+:: cached-result ( n input-cache input quot -- result )
   #! Get the cached result for input position n
   #! from the input cache. If the item is not in the cache,
   #! call 'quot' with 'input' on the stack to get the result
   #! and store that in the cache and return it.
-  [ nip ] swap compose curry cache ; inline
+  n input-cache [ drop input quot call ] cache ; inline
 
 :: run-packrat-parser ( input quot c -- result )
   input input-from