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63 lines
1.8 KiB
Go
63 lines
1.8 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 result
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import (
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"fmt"
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F "github.com/IBM/fp-go/v2/function"
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N "github.com/IBM/fp-go/v2/number"
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)
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func Example_extraction() {
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leftValue, leftErr := Left[int](fmt.Errorf("Division by Zero!"))
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rightValue, rightErr := Right(10)
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// Convert Either[A] to A with a default value
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leftWithDefault := GetOrElse(F.Constant1[error](0))(leftValue, leftErr) // 0
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rightWithDefault := GetOrElse(F.Constant1[error](0))(rightValue, rightErr) // 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(int, error) int
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doubleFromLeft := doubleOrZero(leftValue, leftErr) // 0
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doubleFromRight := doubleOrZero(rightValue, rightErr) // 20
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// You can also chain operations using Map
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tripled, tripledErr := Pipe2(
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rightValue,
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Right[int],
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Map(N.Mul(3)),
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)
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tripledResult := GetOrElse(F.Constant1[error](0))(tripled, tripledErr) // 30
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fmt.Println(ToString(leftValue, leftErr))
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fmt.Println(ToString(rightValue, rightErr))
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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(tripledResult)
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// Output:
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// Left(Division by Zero!)
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// Right[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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// 30
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}
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