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40 lines
1.2 KiB
Go
40 lines
1.2 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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T "github.com/IBM/fp-go/tuple"
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)
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func Scan[GV ~func() O.Option[T.Tuple2[GV, V]], GU ~func() O.Option[T.Tuple2[GU, U]], FCT ~func(V, U) V, U, V any](f FCT, initial V) func(ma GU) GV {
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// pre-declare to avoid cyclic reference
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var recurse func(ma GU, v V) GV
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recurse = func(ma GU, current V) GV {
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return F.Nullary2(
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ma,
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O.Map(func(t T.Tuple2[GU, U]) T.Tuple2[GV, V] {
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v := f(current, t.F2)
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return T.MakeTuple2(recurse(t.F1, v), v)
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}),
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)
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}
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return F.Bind2nd(recurse, initial)
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}
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