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reverse.go
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reverse.go
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package go2linq
import (
"sync"
"github.com/solsw/errorhelper"
)
// Reimplementing LINQ to Objects: Part 27 - Reverse
// https://codeblog.jonskeet.uk/2011/01/08/reimplementing-linq-to-objects-part-27-reverse/
// https://learn.microsoft.com/dotnet/api/system.linq.enumerable.reverse
func factoryReverse[Source any](source Enumerable[Source]) func() Enumerator[Source] {
return func() Enumerator[Source] {
var once sync.Once
var sl []Source
var i int
return enrFunc[Source]{
mvNxt: func() bool {
once.Do(func() { sl = ToSliceMust(source); i = len(sl) })
if i > 0 {
i--
return true
}
return false
},
crrnt: func() Source { return sl[i] },
rst: func() { i = len(sl) },
}
}
}
// [Reverse] inverts the order of the elements in a sequence.
//
// [Reverse]: https://learn.microsoft.com/dotnet/api/system.linq.enumerable.reverse
func Reverse[Source any](source Enumerable[Source]) (Enumerable[Source], error) {
if source == nil {
return nil, errorhelper.CallerError(ErrNilSource)
}
return OnFactory(factoryReverse(source)), nil
}
// ReverseMust is like [Reverse] but panics in case of error.
func ReverseMust[Source any](source Enumerable[Source]) Enumerable[Source] {
return errorhelper.Must(Reverse(source))
}