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examples_extract_test.go
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examples_extract_test.go
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// Copyright (c) 2023 IBM Corp.
// All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package option
import (
"fmt"
F "github.com/IBM/fp-go/function"
N "github.com/IBM/fp-go/number"
)
func ExampleOption_extraction() {
noneValue := None[int]()
someValue := Of(42)
// Convert Option[T] to T
fromNone, okFromNone := Unwrap(noneValue) // 0, false
fromSome, okFromSome := Unwrap(someValue) // 42, true
// Convert Option[T] with a default value
noneWithDefault := GetOrElse(F.Constant(0))(noneValue) // 0
someWithDefault := GetOrElse(F.Constant(0))(someValue) // 42
// Apply a different function on None/Some(...)
doubleOrZero := Fold(
F.Constant(0), // none case
N.Mul(2), // some case
) // func(ma Option[int]) int
doubleFromNone := doubleOrZero(noneValue) // 0
doubleFromSome := doubleOrZero(someValue) // 84
// Pro-tip: Fold is short for the following:
doubleOfZeroBis := F.Flow2(
Map(N.Mul(2)), // some case
GetOrElse(F.Constant(0)), // none case
)
doubleFromNoneBis := doubleOfZeroBis(noneValue) // 0
doubleFromSomeBis := doubleOfZeroBis(someValue) // 84
fmt.Printf("%d, %t\n", fromNone, okFromNone)
fmt.Printf("%d, %t\n", fromSome, okFromSome)
fmt.Println(noneWithDefault)
fmt.Println(someWithDefault)
fmt.Println(doubleFromNone)
fmt.Println(doubleFromSome)
fmt.Println(doubleFromNoneBis)
fmt.Println(doubleFromSomeBis)
// Output:
// 0, false
// 42, true
// 0
// 42
// 0
// 84
// 0
// 84
}