Huangzj
49 lines
1003 B
Go
49 lines
1003 B
Go
package linq
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// Group is a type that is used to store the result of GroupBy method.
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type Group struct {
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Key interface{}
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Group []interface{}
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}
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// GroupBy method groups the elements of a collection according
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// to a specified key selector function and projects the elements for each group
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// by using a specified function.
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func (q Query) GroupBy(
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keySelector func(interface{}) interface{},
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elementSelector func(interface{}) interface{},
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) Query {
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return Query{
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func() Iterator {
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next := q.Iterate()
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set := make(map[interface{}][]interface{})
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for item, ok := next(); ok; item, ok = next() {
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key := keySelector(item)
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set[key] = append(set[key], elementSelector(item))
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}
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len := len(set)
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idx := 0
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groups := make([]Group, len)
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for k, v := range set {
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groups[idx] = Group{k, v}
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idx++
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}
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index := 0
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return func() (item interface{}, ok bool) {
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ok = index < len
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if ok {
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item = groups[index]
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index++
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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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