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50 lines
1.5 KiB
Go
50 lines
1.5 KiB
Go
// Copyright (c) 2023 IBM Corp.
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// All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package generic
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import (
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F "github.com/IBM/fp-go/function"
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O "github.com/IBM/fp-go/option"
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P "github.com/IBM/fp-go/predicate"
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T "github.com/IBM/fp-go/tuple"
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)
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// DropWhile creates an [Iterator] that drops elements from the [Iterator] as long as the predicate is true; afterwards, returns every element.
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// Note, the [Iterator] does not produce any output until the predicate first becomes false
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func DropWhile[GU ~func() O.Option[T.Tuple2[GU, U]], U any](pred func(U) bool) func(GU) GU {
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// avoid cyclic references
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var m func(O.Option[T.Tuple2[GU, U]]) O.Option[T.Tuple2[GU, U]]
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fromPred := O.FromPredicate(P.Not(P.ContraMap(T.Second[GU, U])(pred)))
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recurse := func(mu GU) GU {
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return F.Nullary2(
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mu,
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m,
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)
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}
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m = O.Chain(func(t T.Tuple2[GU, U]) O.Option[T.Tuple2[GU, U]] {
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return F.Pipe2(
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t,
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fromPred,
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O.Fold(recurse(Next(t)), O.Of[T.Tuple2[GU, U]]),
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)
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})
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return recurse
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}
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