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65 lines
1.9 KiB
Go
65 lines
1.9 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 either
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import (
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"fmt"
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F "github.com/IBM/fp-go/function"
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N "github.com/IBM/fp-go/number"
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)
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func ExampleEither_extraction() {
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leftValue := Left[int](fmt.Errorf("Division by Zero!"))
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rightValue := Right[error](10)
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// Convert Either[E, A] to A with a default value
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leftWithDefault := GetOrElse(F.Constant1[error](0))(leftValue) // 0
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rightWithDefault := GetOrElse(F.Constant1[error](0))(rightValue) // 10
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// Apply a different function on Left(...)/Right(...)
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doubleOrZero := Fold(F.Constant1[error](0), N.Mul(2)) // func(Either[error, int]) int
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doubleFromLeft := doubleOrZero(leftValue) // 0
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doubleFromRight := doubleOrZero(rightValue) // 20
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// Pro-tip: Fold is short for the following:
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doubleOrZeroBis := F.Flow2(
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Map[error](N.Mul(2)),
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GetOrElse(F.Constant1[error](0)),
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)
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doubleFromLeftBis := doubleOrZeroBis(leftValue) // 0
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doubleFromRightBis := doubleOrZeroBis(rightValue) // 20
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fmt.Println(leftValue)
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fmt.Println(rightValue)
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fmt.Println(leftWithDefault)
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fmt.Println(rightWithDefault)
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fmt.Println(doubleFromLeft)
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fmt.Println(doubleFromRight)
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fmt.Println(doubleFromLeftBis)
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fmt.Println(doubleFromRightBis)
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// Output:
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// Left[*errors.errorString, int](Division by Zero!)
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// Right[<nil>, int](10)
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// 0
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// 10
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// 0
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// 20
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// 0
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// 20
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}
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