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63 lines
1.9 KiB
Go
63 lines
1.9 KiB
Go
// Copyright (c) 2023 - 2025 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 either
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// WithResource constructs a function that creates a resource, operates on it, and then releases it.
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// This ensures proper resource cleanup even if operations fail.
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// The resource is released immediately after the operation completes.
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//
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// Parameters:
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// - onCreate: Function to create/acquire the resource
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// - onRelease: Function to release/cleanup the resource
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//
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// Returns a function that takes an operation to perform on the resource.
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//
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// Example:
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//
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// withFile := either.WithResource(
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// func() either.Either[error, *os.File] {
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// return either.TryCatchError(os.Open("file.txt"))
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// },
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// func(f *os.File) either.Either[error, any] {
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// return either.TryCatchError(f.Close())
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// },
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// )
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// result := withFile(func(f *os.File) either.Either[error, string] {
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// // Use file here
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// return either.Right[error]("data")
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// })
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func WithResource[A, E, R, ANY any](
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onCreate func() Either[E, R],
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onRelease Kleisli[E, R, ANY],
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) Kleisli[E, Kleisli[E, R, A], A] {
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return func(f func(R) Either[E, A]) Either[E, A] {
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r := onCreate()
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if r.isLeft {
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return Left[A](r.l)
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}
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a := f(r.r)
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n := onRelease(r.r)
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if a.isLeft {
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return Left[A](a.l)
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}
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if n.isLeft {
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return Left[A](n.l)
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}
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return Of[E](a.r)
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}
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}
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