utils.go: Copy and Clone maps with filter function. Also added isIterator().

utils.go

@@ -4,7 +4,9 @@
 // utils.go
 package expr
 
-import "reflect"
+import (
+	"reflect"
+)
 
 func isString(v any) (ok bool) {
 	_, ok = v.(string)
@@ -44,6 +46,11 @@ func isFunctor(v any) (ok bool) {
 	return
 }
 
+func isIterator(v any) (ok bool) {
+	_, ok = v.(Iterator)
+	return
+}
+
 func numAsFloat(v any) (f float64) {
 	var ok bool
 	if f, ok = v.(float64); !ok {
@@ -141,3 +148,23 @@ func CloneMap[K comparable, V any](source map[K]V) map[K]V {
 	dest := make(map[K]V, len(source))
 	return CopyMap(dest, source)
 }
+
+func CopyFilteredMap[K comparable, V any](dest, source map[K]V, filter func(key K) (accept bool)) map[K]V {
+	// fmt.Printf("--- Clone with filter %p\n", filter)
+	if filter == nil {
+		return CopyMap(dest, source)
+	} else {
+		for k, v := range source {
+			if filter(k) {
+				// fmt.Printf("\tClone var %q\n", k)
+				dest[k] = v
+			}
+		}
+	}
+	return dest
+}
+
+func CloneFilteredMap[K comparable, V any](source map[K]V, filter func(key K) (accept bool)) map[K]V {
+	dest := make(map[K]V, len(source))
+	return CopyFilteredMap(dest, source, filter)
+}