feat(Go-Tool)：2020/11/12:新增linq包使用示例(未完成)

vendor/github.com/ahmetalpbalkan/go-linq/select.go

@@ -0,0 +1,71 @@
+package linq
+
+// Select projects each element of a collection into a new form.
+// Returns a query with the result of invoking the transform function
+// on each element of original source.
+//
+// This projection method requires the transform function, selector,
+// to produce one value for each value in the source collection.
+// If selector returns a value that is itself a collection,
+// it is up to the consumer to traverse the subcollections manually.
+// In such a situation, it might be better for your query to return a single
+// coalesced collection of values. To achieve this, use the SelectMany method
+// instead of Select. Although SelectMany works similarly to Select,
+// it differs in that the transform function returns a collection
+// that is then expanded by SelectMany before it is returned.
+func (q Query) Select(selector func(interface{}) interface{}) Query {
+	return Query{
+		Iterate: func() Iterator {
+			next := q.Iterate()
+
+			return func() (item interface{}, ok bool) {
+				var it interface{}
+				it, ok = next()
+				if ok {
+					item = selector(it)
+				}
+
+				return
+			}
+		},
+	}
+}
+
+// SelectIndexed projects each element of a collection into a new form
+// by incorporating the element's index. Returns a query with the result
+// of invoking the transform function on each element of original source.
+//
+// The first argument to selector represents the zero-based index of that element
+// in the source collection. This can be useful if the elements are in a known order
+// and you want to do something with an element at a particular index,
+// for example. It can also be useful if you want to retrieve the index of one
+// or more elements. The second argument to selector represents the element to process.
+//
+// This projection method requires the transform function, selector,
+// to produce one value for each value in the source collection.
+// If selector returns a value that is itself a collection,
+// it is up to the consumer to traverse the subcollections manually.
+// In such a situation, it might be better for your query to return a single
+// coalesced collection of values. To achieve this, use the SelectMany method
+// instead of Select. Although SelectMany works similarly to Select,
+// it differs in that the transform function returns a collection
+// that is then expanded by SelectMany before it is returned.
+func (q Query) SelectIndexed(selector func(int, interface{}) interface{}) Query {
+	return Query{
+		Iterate: func() Iterator {
+			next := q.Iterate()
+			index := 0
+
+			return func() (item interface{}, ok bool) {
+				var it interface{}
+				it, ok = next()
+				if ok {
+					item = selector(index, it)
+					index++
+				}
+
+				return
+			}
+		},
+	}
+}