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

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

@@ -0,0 +1,75 @@
+package linq
+
+// Distinct method returns distinct elements from a collection.
+// The result is an unordered collection that contains no duplicate values.
+func (q Query) Distinct() Query {
+	return Query{
+		Iterate: func() Iterator {
+			next := q.Iterate()
+			set := make(map[interface{}]bool)
+
+			return func() (item interface{}, ok bool) {
+				for item, ok = next(); ok; item, ok = next() {
+					if _, has := set[item]; !has {
+						set[item] = true
+						return
+					}
+				}
+
+				return
+			}
+		},
+	}
+}
+
+// Distinct method returns distinct elements from a collection.
+// The result is an ordered collection that contains no duplicate values.
+//
+// NOTE: Distinct method on OrderedQuery type has better performance than
+// Distinct method on Query type
+func (oq OrderedQuery) Distinct() OrderedQuery {
+	return OrderedQuery{
+		orders: oq.orders,
+		Query: Query{
+			Iterate: func() Iterator {
+				next := oq.Iterate()
+				var prev interface{}
+
+				return func() (item interface{}, ok bool) {
+					for item, ok = next(); ok; item, ok = next() {
+						if item != prev {
+							prev = item
+							return
+						}
+					}
+
+					return
+				}
+			},
+		},
+	}
+}
+
+// DistinctBy method returns distinct elements from a collection. This method
+// executes selector function for each element to determine a value to compare.
+// The result is an unordered collection that contains no duplicate values.
+func (q Query) DistinctBy(selector func(interface{}) interface{}) Query {
+	return Query{
+		Iterate: func() Iterator {
+			next := q.Iterate()
+			set := make(map[interface{}]bool)
+
+			return func() (item interface{}, ok bool) {
+				for item, ok = next(); ok; item, ok = next() {
+					s := selector(item)
+					if _, has := set[s]; !has {
+						set[s] = true
+						return
+					}
+				}
+
+				return
+			}
+		},
+	}
+}