mirror of
https://github.com/IBM/fp-go.git
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279 lines
7.7 KiB
Go
279 lines
7.7 KiB
Go
// Copyright (c) 2023 - 2025 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 lazy
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import (
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L "github.com/IBM/fp-go/v2/optics/lens"
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"github.com/IBM/fp-go/v2/io"
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)
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// Do creates an empty context of type [S] to be used with the [Bind] operation.
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// This is the starting point for do-notation style composition.
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//
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// Example:
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//
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// type State struct {
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// Config Config
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// Data Data
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// }
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// result := lazy.Do(State{})
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func Do[S any](
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empty S,
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) Lazy[S] {
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return io.Do(empty)
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}
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// Bind attaches the result of a computation to a context [S1] to produce a context [S2].
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// This enables sequential composition where each step can depend on the results of previous steps.
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//
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// The setter function takes the result of the computation and returns a function that
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// updates the context from S1 to S2.
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//
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// Example:
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//
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// type State struct {
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// Config Config
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// Data Data
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// }
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//
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// result := F.Pipe2(
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// lazy.Do(State{}),
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// lazy.Bind(
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// func(cfg Config) func(State) State {
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// return func(s State) State { s.Config = cfg; return s }
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// },
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// func(s State) lazy.Lazy[Config] {
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// return lazy.MakeLazy(func() Config { return loadConfig() })
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// },
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// ),
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// lazy.Bind(
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// func(data Data) func(State) State {
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// return func(s State) State { s.Data = data; return s }
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// },
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// func(s State) lazy.Lazy[Data] {
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// // This can access s.Config from the previous step
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// return lazy.MakeLazy(func() Data { return loadData(s.Config) })
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// },
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// ),
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// )
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func Bind[S1, S2, T any](
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setter func(T) func(S1) S2,
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f Kleisli[S1, T],
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) Kleisli[Lazy[S1], S2] {
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return io.Bind(setter, f)
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}
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// Let attaches the result of a computation to a context [S1] to produce a context [S2]
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func Let[S1, S2, T any](
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setter func(T) func(S1) S2,
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f func(S1) T,
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) Kleisli[Lazy[S1], S2] {
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return io.Let(setter, f)
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}
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// LetTo attaches the a value to a context [S1] to produce a context [S2]
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func LetTo[S1, S2, T any](
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setter func(T) func(S1) S2,
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b T,
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) Kleisli[Lazy[S1], S2] {
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return io.LetTo(setter, b)
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}
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// BindTo initializes a new state [S1] from a value [T]
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func BindTo[S1, T any](
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setter func(T) S1,
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) Kleisli[Lazy[T], S1] {
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return io.BindTo(setter)
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}
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// ApS attaches a value to a context [S1] to produce a context [S2] by considering
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// the context and the value concurrently (using Applicative rather than Monad).
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// This allows independent computations to be combined without one depending on the result of the other.
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//
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// Unlike Bind, which sequences operations, ApS can be used when operations are independent
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// and can conceptually run in parallel.
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//
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// Example:
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//
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// type State struct {
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// Config Config
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// Data Data
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// }
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//
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// // These operations are independent and can be combined with ApS
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// getConfig := lazy.MakeLazy(func() Config { return loadConfig() })
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// getData := lazy.MakeLazy(func() Data { return loadData() })
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//
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// result := F.Pipe2(
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// lazy.Do(State{}),
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// lazy.ApS(
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// func(cfg Config) func(State) State {
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// return func(s State) State { s.Config = cfg; return s }
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// },
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// getConfig,
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// ),
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// lazy.ApS(
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// func(data Data) func(State) State {
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// return func(s State) State { s.Data = data; return s }
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// },
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// getData,
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// ),
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// )
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func ApS[S1, S2, T any](
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setter func(T) func(S1) S2,
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fa Lazy[T],
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) Kleisli[Lazy[S1], S2] {
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return io.ApS(setter, fa)
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}
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// ApSL is a variant of ApS that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. This allows you to work with nested fields without manually managing
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// the update logic.
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//
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// Example:
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//
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// type Config struct {
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// Host string
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// Port int
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// }
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// type State struct {
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// Config Config
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// Data string
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// }
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//
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// configLens := L.Prop[State, Config]("Config")
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// getConfig := lazy.MakeLazy(func() Config { return Config{Host: "localhost", Port: 8080} })
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//
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// result := F.Pipe2(
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// lazy.Do(State{}),
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// lazy.ApSL(configLens, getConfig),
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// )
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func ApSL[S, T any](
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lens L.Lens[S, T],
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fa Lazy[T],
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) Kleisli[Lazy[S], S] {
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return io.ApSL(lens, fa)
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}
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// BindL is a variant of Bind that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. The function f receives the current value of the focused field and
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// returns a new computation that produces an updated value.
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//
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// Example:
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//
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// type Config struct {
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// Host string
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// Port int
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// }
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// type State struct {
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// Config Config
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// Data string
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// }
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//
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// configLens := L.Prop[State, Config]("Config")
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//
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// result := F.Pipe2(
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// lazy.Do(State{Config: Config{Host: "localhost"}}),
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// lazy.BindL(configLens, func(cfg Config) lazy.Lazy[Config] {
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// return lazy.MakeLazy(func() Config {
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// cfg.Port = 8080
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// return cfg
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// })
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// }),
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// )
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func BindL[S, T any](
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lens L.Lens[S, T],
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f Kleisli[T, T],
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) Kleisli[Lazy[S], S] {
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return io.BindL(lens, f)
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}
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// LetL is a variant of Let that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. The function f receives the current value of the focused field and
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// returns a new value (without wrapping in a monad).
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//
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// Example:
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//
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// type Config struct {
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// Host string
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// Port int
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// }
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// type State struct {
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// Config Config
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// Data string
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// }
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//
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// configLens := L.Prop[State, Config]("Config")
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//
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// result := F.Pipe2(
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// lazy.Do(State{Config: Config{Host: "localhost"}}),
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// lazy.LetL(configLens, func(cfg Config) Config {
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// cfg.Port = 8080
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// return cfg
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// }),
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// )
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func LetL[S, T any](
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lens L.Lens[S, T],
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f func(T) T,
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) Kleisli[Lazy[S], S] {
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return io.LetL(lens, f)
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}
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// LetToL is a variant of LetTo that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. The value b is set directly to the focused field.
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//
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// Example:
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//
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// type Config struct {
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// Host string
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// Port int
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// }
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// type State struct {
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// Config Config
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// Data string
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// }
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//
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// configLens := L.Prop[State, Config]("Config")
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// newConfig := Config{Host: "localhost", Port: 8080}
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//
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// result := F.Pipe2(
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// lazy.Do(State{}),
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// lazy.LetToL(configLens, newConfig),
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// )
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func LetToL[S, T any](
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lens L.Lens[S, T],
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b T,
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) Kleisli[Lazy[S], S] {
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return io.LetToL(lens, b)
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}
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