issue47272.go

     1  // run
     2  
     3  // Copyright 2021 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  package main
     8  
     9  import (
    10  	"errors"
    11  	"fmt"
    12  )
    13  
    14  type Option[T any] struct {
    15  	ok  bool
    16  	val T
    17  }
    18  
    19  func (o Option[T]) String() string {
    20  	if o.ok {
    21  		return fmt.Sprintf("Some(%v)", o.val)
    22  	}
    23  	return "None"
    24  }
    25  
    26  func Some[T any](val T) Option[T] { return Option[T]{ok: true, val: val} }
    27  func None[T any]() Option[T]      { return Option[T]{ok: false} }
    28  
    29  type Result[T, E any] struct {
    30  	ok  bool
    31  	val T
    32  	err E
    33  }
    34  
    35  func (r Result[T, E]) String() string {
    36  	if r.ok {
    37  		return fmt.Sprintf("Ok(%v)", r.val)
    38  	}
    39  	return fmt.Sprintf("Err(%v)", r.err)
    40  }
    41  
    42  func Ok[T, E any](val T) Result[T, E]  { return Result[T, E]{ok: true, val: val} }
    43  func Err[T, E any](err E) Result[T, E] { return Result[T, E]{ok: false, err: err} }
    44  
    45  func main() {
    46  	a := Some[int](1)
    47  	b := None[int]()
    48  	fmt.Println(a, b)
    49  
    50  	x := Ok[int, error](1)
    51  	y := Err[int, error](errors.New("test"))
    52  	fmt.Println(x, y)
    53  	// fmt.Println(x)
    54  	_, _, _, _ = a, b, x, y
    55  }
    56
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