Improved pair parsing

Rick Button · Rick Button · commit f6d3afd47866 · 2017-08-15T23:12:53.000-05:00
diff --git a/src/Scheme.NET/Parser/Visitors/SchemeVisitor.cs b/src/Scheme.NET/Parser/Visitors/SchemeVisitor.cs
@@ -37,25 +37,27 @@ public override object VisitIdentifier([NotNull] SchemeParser.IdentifierContext
 
         public override object VisitList([NotNull] SchemeParser.ListContext context)
         {
-            var elements = context.datumOrPair();
+            var elements = context.datum();
 
             return CreateList(elements);
         }
 
-        private object CreateList(SchemeParser.DatumOrPairContext[] elements)
+        public override object VisitPair([NotNull] SchemeParser.PairContext context)
+        {
+            var elements = context.datum();
+            return CreatePair(elements);
+        }
+
+        private object CreateList(SchemeParser.DatumContext[] elements)
         {
             if (elements.Length == 0)
                 return AtomHelper.Nil;
 
-            if (elements.First().datum() == null)
-                return CreatePair(elements.First().pair());
-
             return AtomHelper.CreateCons((ISExpression)Visit(elements.First()), (ISExpression)CreateList(elements.Skip(1).ToArray()));
         }
 
-        private object CreatePair(SchemeParser.PairContext context)
+        private object CreatePair(SchemeParser.DatumContext[] elements)
         {
-            var elements = context.datum().ToArray();
             return AtomHelper.CreateCons((ISExpression)Visit(elements[0]), (ISExpression)Visit(elements[1]));
         }
 
diff --git a/src/Scheme.NET/Scheme.g4 b/src/Scheme.NET/Scheme.g4
@@ -9,10 +9,6 @@ options {
 
 // Parser rules
 
-datumOrPair : pair
-            | datum;
-
-
 datum : simpleDatum
       | compoundDatum
       ;
@@ -25,14 +21,15 @@ simpleDatum : bool
             ;
 
 compoundDatum : list
+              | pair
               | vector
               | quote
               | abbreviation
               ;
 
-list : '(' datumOrPair* ')';
+list : '(' datum* ')';
 
-pair : datum '.' datum;
+pair : '(' datum '.' datum ')';
 
 bool : TRUE              # True
      | FALSE             # False

Original file line number	Diff line number	Diff line change
`@@ -37,25 +37,27 @@ public override object VisitIdentifier([NotNull] SchemeParser.IdentifierContext`
`37`	`37`
`38`	`38`	`public override object VisitList([NotNull] SchemeParser.ListContext context)`
`39`	`39`	`{`
`40`		`- var elements = context.datumOrPair();`
	`40`	`+ var elements = context.datum();`
`41`	`41`
`42`	`42`	`return CreateList(elements);`
`43`	`43`	`}`
`44`	`44`
`45`		`- private object CreateList(SchemeParser.DatumOrPairContext[] elements)`
	`45`	`+ public override object VisitPair([NotNull] SchemeParser.PairContext context)`
	`46`	`+ {`
	`47`	`+ var elements = context.datum();`
	`48`	`+ return CreatePair(elements);`
	`49`	`+ }`
	`50`	`+`
	`51`	`+ private object CreateList(SchemeParser.DatumContext[] elements)`
`46`	`52`	`{`
`47`	`53`	`if (elements.Length == 0)`
`48`	`54`	`return AtomHelper.Nil;`
`49`	`55`
`50`		`- if (elements.First().datum() == null)`
`51`		`- return CreatePair(elements.First().pair());`
`52`		`-`
`53`	`56`	`return AtomHelper.CreateCons((ISExpression)Visit(elements.First()), (ISExpression)CreateList(elements.Skip(1).ToArray()));`
`54`	`57`	`}`
`55`	`58`
`56`		`- private object CreatePair(SchemeParser.PairContext context)`
	`59`	`+ private object CreatePair(SchemeParser.DatumContext[] elements)`
`57`	`60`	`{`
`58`		`- var elements = context.datum().ToArray();`
`59`	`61`	`return AtomHelper.CreateCons((ISExpression)Visit(elements[0]), (ISExpression)Visit(elements[1]));`
`60`	`62`	`}`
`61`	`63`