3 files changed, 43 insertions, 0 deletions
diff --git a/subex/filter.go b/subex/filter.go
index ae4b8ab..309d6c7 100644
--- a/subex/filter.go
+++ b/subex/filter.go
@@ -27,6 +27,26 @@ func (_ anyBoolFilter) valueFilter(value walk.Value) bool {
 	return isBool
 }
 
+type simpleValueFilter struct {}
+func (_ simpleValueFilter) valueFilter(value walk.Value) bool {
+	switch value := value.(type) {
+	case walk.NullValue:
+		return true
+	case walk.BoolValue:
+		return true
+	case walk.NumberValue:
+		return true
+	case walk.StringValue:
+		return true
+	case walk.ArrayValue:
+		return len(value) == 0
+	case walk.MapValue:
+		return len(value) == 0
+	default:
+		panic("Invalid value type")
+	}
+}
+
 type anyValueFilter struct {}
 func (_ anyValueFilter) valueFilter(value walk.Value) bool {
 	return true
diff --git a/subex/parse.go b/subex/parse.go
index 9a7a75c..e91008a 100644
--- a/subex/parse.go
+++ b/subex/parse.go
@@ -520,6 +520,17 @@ func parseSubex(l RuneReader, minPower int, inType Type) (lhs SubexAST, outType
 			} else {
 				lhs = SubexASTCopyAnyValue{}
 			}
+		case ',':
+			switch inType {
+			case ValueType:
+				outType = inType
+				lhs = SubexASTCopyAnySimpleValue{}
+			case RuneType:
+				outType = inType
+				lhs = SubexASTCopyRune{','}
+			default:
+				panic("Invalid inType")
+			}
 		case '?':
 			outType = inType
 			lhs = SubexASTCopyBool{}
diff --git a/subex/subexast.go b/subex/subexast.go
index d08ddac..655a783 100644
--- a/subex/subexast.go
+++ b/subex/subexast.go
@@ -238,6 +238,18 @@ func (ast SubexASTCopyNumber) String() string {
 	return "%"
 }
 
+// Read in a null, bool, number, string or empty array or map and output it unchanged
+type SubexASTCopyAnySimpleValue struct {}
+func (ast SubexASTCopyAnySimpleValue) compileWith(next SubexState, slotMap *SlotMap, inType Type, outType Type) SubexState {
+	if inType != ValueType || outType != ValueType {
+		panic("Invalid types for SubexASTCopyAnySimpleValue")
+	}
+	return &SubexCopyState {
+		next: next,
+		filter: simpleValueFilter{},
+	}
+}
+
 // Read in any single Atom and output it unchanged
 type SubexASTCopyAnyValue struct {}
 func (ast SubexASTCopyAnyValue) compileWith(next SubexState, slotMap *SlotMap, inType Type, outType Type) SubexState {