Fixed two seg faults and added lists:add

ucl/builtins.go

@@ -517,7 +517,7 @@ func keysBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 		}); err != nil {
 			return nil, err
 		}
-		return keys, nil
+		return &keys, nil
 	}
 
 	return nil, nil
@@ -545,7 +545,7 @@ func mapBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 			}
 			newList = append(newList, m)
 		}
-		return newList, nil
+		return &newList, nil
 	}
 	return nil, errors.New("expected listable")
 }
@@ -569,17 +569,17 @@ func filterBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 			m, err := inv.invoke(ctx, args.fork([]Object{v}))
 			if err != nil {
 				return nil, err
-			} else if m.Truthy() {
+			} else if m != nil && m.Truthy() {
 				newList = append(newList, v)
 			}
 		}
-		return newList, nil
+		return &newList, nil
 	case hashable:
 		newHash := hashObject{}
 		if err := t.Each(func(k string, v Object) error {
 			if m, err := inv.invoke(ctx, args.fork([]Object{StringObject(k), v})); err != nil {
 				return err
-			} else if m.Truthy() {
+			} else if m != nil && m.Truthy() {
 				newHash[k] = v
 			}
 			return nil

ucl/builtins/csv.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"io"
 	"io/fs"
+	"os"
 	"strings"
 	"ucl.lmika.dev/ucl"
 )
@@ -25,6 +26,13 @@ func CSV(fs fs.FS) ucl.Module {
 	}
 }
 
+func (h csvHandlers) openFile(name string) (fs.File, error) {
+	if h.fs == nil {
+		return os.Open(name)
+	}
+	return h.fs.Open(name)
+}
+
 func (h csvHandlers) eachRecord(ctx context.Context, args ucl.CallArgs) (any, error) {
 	var (
 		filename string
@@ -35,7 +43,7 @@ func (h csvHandlers) eachRecord(ctx context.Context, args ucl.CallArgs) (any, er
 		return nil, err
 	}
 
-	f, err := h.fs.Open(filename)
+	f, err := h.openFile(filename)
 	if err != nil {
 		return nil, err
 	}

ucl/eval.go

@@ -203,7 +203,7 @@ func (e evaluator) evalArg(ctx context.Context, ec *evalCtx, n astCmdArg) (Objec
 
 func (e evaluator) evalListOrHash(ctx context.Context, ec *evalCtx, loh *astListOrHash) (Object, error) {
 	if loh.EmptyList {
-		return listObject{}, nil
+		return &listObject{}, nil
 	} else if loh.EmptyHash {
 		return hashObject{}, nil
 	}
@@ -241,7 +241,7 @@ func (e evaluator) evalListOrHash(ctx context.Context, ec *evalCtx, loh *astList
 		}
 		l = append(l, v)
 	}
-	return l, nil
+	return &l, nil
 }
 
 func (e evaluator) evalLiteral(ctx context.Context, ec *evalCtx, n *astLiteral) (Object, error) {

ucl/objs.go

@@ -22,6 +22,16 @@ type Listable interface {
 	Index(i int) Object
 }
 
+type ModListable interface {
+	Listable
+
+	// Insert adds a new item to the list. idx can be a positive
+	// number from 0 to len(), in which case the object will be inserted
+	// at that position.  If idx is negative, then the item will be inserted
+	// at that position from the right.
+	Insert(idx int, obj Object) error
+}
+
 type hashable interface {
 	Len() int
 	Value(k string) Object
@@ -34,20 +44,32 @@ func (lo *listObject) Append(o Object) {
 	*lo = append(*lo, o)
 }
 
-func (s listObject) String() string {
-	return fmt.Sprintf("%v", []Object(s))
+func (lo *listObject) Insert(idx int, obj Object) error {
+	if idx != -1 {
+		return errors.New("not supported")
+	}
+	*lo = append(*lo, obj)
+	return nil
 }
 
-func (s listObject) Truthy() bool {
-	return len(s) > 0
+func (s *listObject) String() string {
+	return fmt.Sprintf("%v", []Object(*s))
 }
 
-func (s listObject) Len() int {
-	return len(s)
+func (s *listObject) Truthy() bool {
+	return len(*s) > 0
 }
 
-func (s listObject) Index(i int) Object {
-	return s[i]
+func (s *listObject) Len() int {
+	return len(*s)
+}
+
+func (s *listObject) Index(i int) Object {
+	return (*s)[i]
+}
+
+func (s *listObject) Add(o Object) {
+	*s = append(*s, o)
 }
 
 type hashObject map[string]Object
@@ -149,9 +171,9 @@ func toGoValue(obj Object) (interface{}, bool) {
 		return bool(v), true
 	case timeObject:
 		return time.Time(v), true
-	case listObject:
-		xs := make([]interface{}, 0, len(v))
-		for _, va := range v {
+	case *listObject:
+		xs := make([]interface{}, 0, len(*v))
+		for _, va := range *v {
 			x, ok := toGoValue(va)
 			if !ok {
 				continue

ucl/testbuiltins_test.go

@@ -38,7 +38,9 @@ func WithTestBuiltin() InstOption {
 		}))
 
 		i.rootEC.addCmd("list", invokableFunc(func(ctx context.Context, args invocationArgs) (Object, error) {
-			return listObject(args.args), nil
+			var a listObject = make([]Object, len(args.args))
+			copy(a, args.args)
+			return &a, nil
 		}))
 
 		i.rootEC.addCmd("error", invokableFunc(func(ctx context.Context, args invocationArgs) (Object, error) {
@@ -1170,6 +1172,8 @@ func TestBuiltins_Filter(t *testing.T) {
 		{desc: "filter list 1", expr: `filter [1 2 3] { |x| eq $x 2 }`, want: []any{2}},
 		{desc: "filter list 2", expr: `filter ["flim" "flam" "fla"] { |x| eq $x "flam" }`, want: []any{"flam"}},
 		{desc: "filter list 3", expr: `filter ["flim" "flam" "fla"] { |x| eq $x "bogie" }`, want: []any{}},
+		{desc: "filter list 4", expr: `filter [() () ()] { |x| $x }`, want: []any{}},
+		{desc: "filter list 5", expr: `filter [] { |x| $x }`, want: []any{}},
 
 		{desc: "filter map 1", expr: `filter [alpha:"hello" bravo:"world"] { |k v| eq $k "alpha" }`, want: map[string]any{
 			"alpha": "hello",

ucl/userbuiltin.go

@@ -121,6 +121,12 @@ func (ca CallArgs) bindArg(v interface{}, arg Object) error {
 		}
 		*t = i
 		return nil
+	case *ModListable:
+		if i, ok := arg.(ModListable); ok {
+			*t = i
+			return nil
+		}
+		return errors.New("exepected listable")
 	case *string:
 		if arg != nil {
 			*t = arg.String()