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