Added reverse op

pkg/yqlib/operator_reverse.go

@@ -0,0 +1,34 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+func reverseOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+	results := list.New()
+
+	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+
+		candidateNode := unwrapDoc(candidate.Node)
+
+		if candidateNode.Kind != yaml.SequenceNode {
+			return context, fmt.Errorf("node at path [%v] is not an array (it's a %v)", candidate.GetNicePath(), candidate.GetNiceTag())
+		}
+
+		reverseList := &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq", Style: candidateNode.Style}
+		reverseList.Content = make([]*yaml.Node, len(candidateNode.Content))
+
+		for i, originalNode := range candidateNode.Content {
+			reverseList.Content[len(candidateNode.Content)-i-1] = originalNode
+		}
+		results.PushBack(candidate.CreateReplacement(reverseList))
+
+	}
+
+	return context.ChildContext(results), nil
+
+}