Huangzj
90 lines
2.2 KiB
Go
90 lines
2.2 KiB
Go
package linq
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// Where filters a collection of values based on a predicate.
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func (q Query) Where(predicate func(interface{}) bool) 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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return func() (item interface{}, ok bool) {
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for item, ok = next(); ok; item, ok = next() {
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if predicate(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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// WhereT is the typed version of Where.
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//
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// - predicateFn is of type "func(TSource)bool"
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//
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// NOTE: Where has better performance than WhereT.
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func (q Query) WhereT(predicateFn interface{}) Query {
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predicateGenericFunc, err := newGenericFunc(
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"WhereT", "predicateFn", predicateFn,
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simpleParamValidator(newElemTypeSlice(new(genericType)), newElemTypeSlice(new(bool))),
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)
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if err != nil {
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panic(err)
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}
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predicateFunc := func(item interface{}) bool {
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return predicateGenericFunc.Call(item).(bool)
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}
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return q.Where(predicateFunc)
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}
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// WhereIndexed filters a collection of values based on a predicate. Each
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// element's index is used in the logic of the predicate function.
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//
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// The first argument represents the zero-based index of the element within
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// collection. The second argument of predicate represents the element to test.
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func (q Query) WhereIndexed(predicate func(int, interface{}) bool) 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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index := 0
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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 predicate(index, item) {
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return
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}
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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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// WhereIndexedT is the typed version of WhereIndexed.
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//
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// - predicateFn is of type "func(int,TSource)bool"
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//
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// NOTE: WhereIndexed has better performance than WhereIndexedT.
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func (q Query) WhereIndexedT(predicateFn interface{}) Query {
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predicateGenericFunc, err := newGenericFunc(
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"WhereIndexedT", "predicateFn", predicateFn,
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simpleParamValidator(newElemTypeSlice(new(int), new(genericType)), newElemTypeSlice(new(bool))),
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)
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if err != nil {
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panic(err)
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}
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predicateFunc := func(index int, item interface{}) bool {
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return predicateGenericFunc.Call(index, item).(bool)
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}
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return q.WhereIndexed(predicateFunc)
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}
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