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53 lines
1.3 KiB
Go
53 lines
1.3 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 monoid
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import (
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S "github.com/IBM/fp-go/semigroup"
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)
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type Monoid[A any] interface {
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S.Semigroup[A]
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Empty() A
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}
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type monoid[A any] struct {
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c func(A, A) A
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e A
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}
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func (self monoid[A]) Concat(x A, y A) A {
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return self.c(x, y)
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}
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func (self monoid[A]) Empty() A {
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return self.e
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}
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// MakeMonoid creates a monoid given a concat function and an empty element
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func MakeMonoid[A any](c func(A, A) A, e A) Monoid[A] {
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return monoid[A]{c: c, e: e}
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}
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// Reverse returns the dual of a `Monoid`, obtained by swapping the arguments of `Concat`.
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func Reverse[A any](m Monoid[A]) Monoid[A] {
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return MakeMonoid(S.Reverse[A](m).Concat, m.Empty())
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}
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func ToSemigroup[A any](m Monoid[A]) S.Semigroup[A] {
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return S.Semigroup[A](m)
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}
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