Fix precedence between choice/sequence in ebnf

extra/peg/ebnf/ebnf-tests.factor

@@ -38,4 +38,17 @@ IN: temporary
   }   
 } [
   "digit = '1' '2'" 'rule' parse parse-result-ast
+] unit-test
+
+{
+  T{ ebnf-choice f
+     V{ 
+       T{ ebnf-sequence f
+          V{ T{ ebnf-non-terminal f "one" } T{ ebnf-non-terminal f "two" } }
+       }
+       T{ ebnf-non-terminal f "three" }
+     }
+  } 
+} [
+  "one two | three" 'choice' parse parse-result-ast
 ] unit-test

extra/peg/ebnf/ebnf.factor

@@ -97,12 +97,15 @@ DEFER: 'rhs'
 
 : 'sequence' ( -- parser )
   'element' sp 
-  "|" token sp ensure-not 2array seq [ first ] action 
-   repeat1 [ <ebnf-sequence> ] action ;
-  
-: 'choice' ( -- parser )
-  'element' sp "|" token sp list-of [ <ebnf-choice> ] action ;
+   repeat1 [ 
+     dup length 1 = [ first ] [ <ebnf-sequence> ] if
+   ] action ;  
 
+: 'choice' ( -- parser )
+  'sequence' sp "|" token sp list-of [ 
+    dup length 1 = [ first ] [ <ebnf-choice> ] if
+   ] action ;
+  
 : 'repeat0' ( -- parser )
   "{" token sp hide
   [ 'rhs' sp ] delay
@@ -116,10 +119,8 @@ DEFER: 'rhs'
 
 : 'rhs' ( -- parser )
   'repeat0'
-  'sequence'
   'choice'
-  'element'
-  4array choice 'action' sp optional 2array seq ;
+  2array choice 'action' sp optional 2array seq ;
  
 : 'rule' ( -- parser )
   'non-terminal' [ ebnf-non-terminal-symbol ] action