Added pipe and length docs, fix pipe precedence

pkg/yqlib/operator_length.go

@@ -0,0 +1,35 @@
+package yqlib
+
+import (
+	"container/list"
+	"fmt"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+func LengthOperator(d *dataTreeNavigator, matchMap *list.List, pathNode *PathTreeNode) (*list.List, error) {
+	log.Debugf("-- lengthOperation")
+	var results = list.New()
+
+	for el := matchMap.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		targetNode := UnwrapDoc(candidate.Node)
+		var length int
+		switch targetNode.Kind {
+		case yaml.ScalarNode:
+			length = len(targetNode.Value)
+		case yaml.MappingNode:
+			length = len(targetNode.Content) / 2
+		case yaml.SequenceNode:
+			length = len(targetNode.Content)
+		default:
+			length = 0
+		}
+
+		node := &yaml.Node{Kind: yaml.ScalarNode, Value: fmt.Sprintf("%v", length), Tag: "!!int"}
+		lengthCand := &CandidateNode{Node: node, Document: candidate.Document, Path: candidate.Path}
+		results.PushBack(lengthCand)
+	}
+
+	return results, nil
+}