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74 lines
1.9 KiB
Go
74 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 option
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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 ExampleOption_extraction() {
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noneValue := None[int]()
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someValue := Of(42)
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// Convert Option[T] to T
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fromNone, okFromNone := Unwrap(noneValue) // 0, false
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fromSome, okFromSome := Unwrap(someValue) // 42, true
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// Convert Option[T] with a default value
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noneWithDefault := GetOrElse(F.Constant(0))(noneValue) // 0
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someWithDefault := GetOrElse(F.Constant(0))(someValue) // 42
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// Apply a different function on None/Some(...)
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doubleOrZero := Fold(
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F.Constant(0), // none case
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N.Mul(2), // some case
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) // func(ma Option[int]) int
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doubleFromNone := doubleOrZero(noneValue) // 0
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doubleFromSome := doubleOrZero(someValue) // 84
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// Pro-tip: Fold is short for the following:
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doubleOfZeroBis := F.Flow2(
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Map(N.Mul(2)), // some case
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GetOrElse(F.Constant(0)), // none case
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)
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doubleFromNoneBis := doubleOfZeroBis(noneValue) // 0
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doubleFromSomeBis := doubleOfZeroBis(someValue) // 84
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fmt.Printf("%d, %t\n", fromNone, okFromNone)
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fmt.Printf("%d, %t\n", fromSome, okFromSome)
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fmt.Println(noneWithDefault)
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fmt.Println(someWithDefault)
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fmt.Println(doubleFromNone)
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fmt.Println(doubleFromSome)
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fmt.Println(doubleFromNoneBis)
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fmt.Println(doubleFromSomeBis)
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// Output:
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// 0, false
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// 42, true
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// 0
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// 42
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// 0
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// 84
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// 0
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// 84
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}
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