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fp-go/state/generic/state.go
Dr. Carsten Leue 01d490b710 fix: add State monad
Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>
2024-02-13 14:23:33 +01:00

132 lines
3.7 KiB
Go

// Copyright (c) 2024 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 generic
import (
F "github.com/IBM/fp-go/function"
C "github.com/IBM/fp-go/internal/chain"
FC "github.com/IBM/fp-go/internal/functor"
P "github.com/IBM/fp-go/pair"
)
var (
undefined any = struct{}{}
)
func Get[GA ~func(S) P.Pair[S, S], S any]() GA {
return P.Of[S]
}
func Gets[GA ~func(S) P.Pair[A, S], FCT ~func(S) A, A, S any](f FCT) GA {
return func(s S) P.Pair[A, S] {
return P.MakePair(f(s), s)
}
}
func Put[GA ~func(S) P.Pair[any, S], S any]() GA {
return F.Bind1st(P.MakePair[any, S], undefined)
}
func Modify[GA ~func(S) P.Pair[any, S], FCT ~func(S) S, S any](f FCT) GA {
return F.Flow2(
f,
F.Bind1st(P.MakePair[any, S], undefined),
)
}
func Of[GA ~func(S) P.Pair[A, S], S, A any](a A) GA {
return F.Bind1st(P.MakePair[A, S], a)
}
func MonadMap[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) B, S, A, B any](fa GA, f FCT) GB {
return func(s S) P.Pair[B, S] {
p2 := fa(s)
return P.MakePair(f(P.Head(p2)), P.Tail(p2))
}
}
func Map[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) B, S, A, B any](f FCT) func(GA) GB {
return F.Bind2nd(MonadMap[GB, GA, FCT, S, A, B], f)
}
func MonadChain[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](fa GA, f FCT) GB {
return func(s S) P.Pair[B, S] {
a := fa(s)
return f(P.Head(a))(P.Tail(a))
}
}
func Chain[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](f FCT) func(GA) GB {
return F.Bind2nd(MonadChain[GB, GA, FCT, S, A, B], f)
}
func MonadAp[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any](fab GAB, fa GA) GB {
return func(s S) P.Pair[B, S] {
f := fab(s)
a := fa(P.Tail(f))
return P.MakePair(P.Head(f)(P.Head(a)), P.Tail(a))
}
}
func Ap[GB ~func(S) P.Pair[B, S], GAB ~func(S) P.Pair[func(A) B, S], GA ~func(S) P.Pair[A, S], S, A, B any](ga GA) func(GAB) GB {
return F.Bind2nd(MonadAp[GB, GAB, GA, S, A, B], ga)
}
func MonadChainFirst[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](ma GA, f FCT) GA {
return C.MonadChainFirst(
MonadChain[GA, GA, func(A) GA],
MonadMap[GA, GB, func(B) A],
ma,
f,
)
}
func ChainFirst[GB ~func(S) P.Pair[B, S], GA ~func(S) P.Pair[A, S], FCT ~func(A) GB, S, A, B any](f FCT) func(GA) GA {
return C.ChainFirst(
Chain[GA, GA, func(A) GA],
Map[GA, GB, func(B) A],
f,
)
}
func Flatten[GAA ~func(S) P.Pair[GA, S], GA ~func(S) P.Pair[A, S], S, A any](mma GAA) GA {
return MonadChain[GA, GAA, func(GA) GA](mma, F.Identity[GA])
}
func Execute[GA ~func(S) P.Pair[A, S], S, A any](s S) func(GA) S {
return func(fa GA) S {
return P.Tail(fa(s))
}
}
func Evaluate[GA ~func(S) P.Pair[A, S], S, A any](s S) func(GA) A {
return func(fa GA) A {
return P.Head(fa(s))
}
}
func MonadFlap[FAB ~func(A) B, GFAB ~func(S) P.Pair[FAB, S], GB ~func(S) P.Pair[B, S], S, A, B any](fab GFAB, a A) GB {
return FC.MonadFlap(
MonadMap[GB, GFAB, func(FAB) B],
fab,
a)
}
func Flap[FAB ~func(A) B, GFAB ~func(S) P.Pair[FAB, S], GB ~func(S) P.Pair[B, S], S, A, B any](a A) func(GFAB) GB {
return FC.Flap(Map[GB, GFAB, func(FAB) B], a)
}