mirror of
https://github.com/IBM/fp-go.git
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50 lines
1.4 KiB
Go
50 lines
1.4 KiB
Go
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// 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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I "github.com/IBM/fp-go/identity"
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L "github.com/IBM/fp-go/optics/lens"
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O "github.com/IBM/fp-go/option"
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RR "github.com/IBM/fp-go/record/generic"
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)
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// AtRecord returns a lens that focusses on a value in a record
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func AtRecord[M ~map[K]V, K comparable, V any](key K) L.Lens[M, O.Option[V]] {
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addKey := F.Bind1of2(RR.UpsertAt[M, K, V])(key)
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delKey := F.Bind1of1(RR.DeleteAt[M, K, V])(key)
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fold := O.Fold(
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delKey,
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addKey,
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)
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return L.MakeLens(
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RR.Lookup[M](key),
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func(m M, v O.Option[V]) M {
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return F.Pipe2(
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v,
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fold,
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I.Ap[M, M](m),
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)
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},
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)
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}
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// AtKey returns a `Lens` focused on a required key of a `ReadonlyRecord`
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func AtKey[M ~map[K]V, S any, K comparable, V any](key K) func(sa L.Lens[S, M]) L.Lens[S, O.Option[V]] {
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return L.Compose[S](AtRecord[M](key))
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}
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