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100 lines
2.1 KiB
Go
100 lines
2.1 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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"bytes"
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"encoding/json"
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"fmt"
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)
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var (
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jsonNull = []byte("null")
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)
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// Option defines a data structure that logically holds a value or not
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type Option[A any] struct {
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isSome bool
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some A
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}
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// String prints some debug info for the object
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func (s Option[A]) String() string {
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if s.isSome {
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return fmt.Sprintf("Some[%T](%v)", s.some, s.some)
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}
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return fmt.Sprintf("None[%T]", s.some)
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}
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// Format prints some debug info for the object
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func (s Option[A]) Format(f fmt.State, c rune) {
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switch c {
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case 's':
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fmt.Fprint(f, s.String())
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default:
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fmt.Fprint(f, s.String())
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}
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}
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func (s Option[A]) MarshalJSON() ([]byte, error) {
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if IsSome(s) {
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return json.Marshal(s.some)
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}
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return jsonNull, nil
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}
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func (s *Option[A]) UnmarshalJSON(data []byte) error {
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// decode the value
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if bytes.Equal(data, jsonNull) {
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s.isSome = false
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s.some = *new(A)
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return nil
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}
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s.isSome = true
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return json.Unmarshal(data, &s.some)
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}
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func IsNone[T any](val Option[T]) bool {
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return !val.isSome
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}
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func Some[T any](value T) Option[T] {
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return Option[T]{isSome: true, some: value}
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}
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func Of[T any](value T) Option[T] {
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return Some(value)
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}
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func None[T any]() Option[T] {
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return Option[T]{isSome: false}
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}
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func IsSome[T any](val Option[T]) bool {
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return val.isSome
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}
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func MonadFold[A, B any](ma Option[A], onNone func() B, onSome func(A) B) B {
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if IsSome(ma) {
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return onSome(ma.some)
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}
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return onNone()
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}
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func Unwrap[A any](ma Option[A]) (A, bool) {
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return ma.some, ma.isSome
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}
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