mirror of
https://github.com/IBM/fp-go.git
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286 lines
7.4 KiB
Go
286 lines
7.4 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 io
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import (
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F "github.com/IBM/fp-go/v2/function"
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INTA "github.com/IBM/fp-go/v2/internal/apply"
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INTC "github.com/IBM/fp-go/v2/internal/chain"
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INTF "github.com/IBM/fp-go/v2/internal/functor"
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L "github.com/IBM/fp-go/v2/optics/lens"
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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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// user User
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// posts []Post
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// }
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// result := pipe.Pipe2(
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// io.Do(State{}),
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// io.Bind("user", fetchUser),
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// io.Bind("posts", func(s State) io.IO[[]Post] {
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// return fetchPosts(s.user.Id)
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// }),
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// )
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func Do[S any](
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empty S,
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) IO[S] {
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return Of(empty)
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}
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// Bind attaches the result of an IO computation to a context S1 to produce a context S2.
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// This is used in do-notation style composition to build up state incrementally.
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//
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// The setter function takes the result T and returns a function that updates S1 to S2.
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//
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// Example:
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//
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// io.Bind(func(user User) func(s State) State {
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// return func(s State) State {
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// s.user = user
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// return s
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// }
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// }, fetchUser)
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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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) Operator[S1, S2] {
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return INTC.Bind(
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Chain[S1, S2],
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Map[T, S2],
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setter,
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f,
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)
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}
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// Let attaches the result of a pure computation to a context S1 to produce a context S2.
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// Similar to Bind, but for pure (non-IO) computations.
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//
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// Example:
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//
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// io.Let(func(count int) func(s State) State {
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// return func(s State) State {
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// s.count = count
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// return s
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// }
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// }, func(s State) int { return len(s.items) })
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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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) Operator[S1, S2] {
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return INTF.Let(
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Map[S1, S2],
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setter,
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f,
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)
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}
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// LetTo attaches a constant value to a context S1 to produce a context S2.
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// Similar to Let, but with a constant value instead of a computation.
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//
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// Example:
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//
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// io.LetTo(func(status string) func(s State) State {
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// return func(s State) State {
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// s.status = status
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// return s
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// }
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// }, "ready")
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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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) Operator[S1, S2] {
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return INTF.LetTo(
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Map[S1, S2],
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setter,
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b,
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)
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}
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// BindTo initializes a new state S1 from a value T.
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// This is typically used to start a do-notation chain from a single value.
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//
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// Example:
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//
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// io.BindTo(func(user User) State {
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// return State{user: user}
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// })
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func BindTo[S1, T any](
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setter func(T) S1,
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) Operator[T, S1] {
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return INTC.BindTo(
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Map[T, S1],
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setter,
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)
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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 operations).
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// This allows parallel execution of independent computations.
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//
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// Example:
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//
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// io.ApS(func(posts []Post) func(s State) State {
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// return func(s State) State {
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// s.posts = posts
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// return s
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// }
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// }, fetchPosts())
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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 IO[T],
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) Operator[S1, S2] {
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return INTA.ApS(
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Ap[S2, T],
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Map[S1, func(T) S2],
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setter,
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fa,
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)
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}
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// ApSL attaches a value to a context using a lens-based setter.
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// This is a convenience function that combines ApS with a lens, allowing you to use
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// optics to update nested structures in a more composable way.
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//
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// The lens parameter provides both the getter and setter for a field within the structure S.
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// This eliminates the need to manually write setter functions.
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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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//
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// portLens := lens.MakeLens(
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// func(c Config) int { return c.Port },
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// func(c Config, p int) Config { c.Port = p; return c },
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// )
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//
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// result := F.Pipe2(
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// io.Of(Config{Host: "localhost"}),
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// io.ApSL(portLens, io.Of(8080)),
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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 IO[T],
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) Operator[S, S] {
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return ApS(lens.Set, fa)
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}
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// BindL attaches the result of a computation to a context using a lens-based setter.
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// This is a convenience function that combines Bind with a lens, allowing you to use
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// optics to update nested structures based on their current values.
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//
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// The lens parameter provides both the getter and setter for a field within the structure S.
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// The computation function f receives the current value of the focused field and returns
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// an IO that produces the new value.
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//
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// Example:
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//
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// type Counter struct {
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// Value int
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// }
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//
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// valueLens := lens.MakeLens(
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// func(c Counter) int { return c.Value },
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// func(c Counter, v int) Counter { c.Value = v; return c },
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// )
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//
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// // Increment the counter asynchronously
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// increment := func(v int) io.IO[int] {
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// return io.Of(v + 1)
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// }
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//
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// result := F.Pipe1(
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// io.Of(Counter{Value: 42}),
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// io.BindL(valueLens, increment),
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// ) // IO[Counter{Value: 43}]
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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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) Operator[S, S] {
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return Bind(lens.Set, F.Flow2(lens.Get, f))
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}
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// LetL attaches the result of a pure computation to a context using a lens-based setter.
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// This is a convenience function that combines Let with a lens, allowing you to use
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// optics to update nested structures with pure transformations.
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//
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// The lens parameter provides both the getter and setter for a field within the structure S.
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// The transformation function f receives the current value of the focused field and returns
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// the new value directly (not wrapped in IO).
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//
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// Example:
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//
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// type Counter struct {
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// Value int
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// }
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//
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// valueLens := lens.MakeLens(
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// func(c Counter) int { return c.Value },
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// func(c Counter, v int) Counter { c.Value = v; return c },
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// )
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//
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// // Double the counter value
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// double := func(v int) int { return v * 2 }
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//
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// result := F.Pipe1(
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// io.Of(Counter{Value: 21}),
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// io.LetL(valueLens, double),
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// ) // IO[Counter{Value: 42}]
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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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) Operator[S, S] {
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return Let(lens.Set, F.Flow2(lens.Get, f))
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}
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// LetToL attaches a constant value to a context using a lens-based setter.
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// This is a convenience function that combines LetTo with a lens, allowing you to use
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// optics to set nested fields to specific values.
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//
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// The lens parameter provides the setter for a field within the structure S.
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// Unlike LetL which transforms the current value, LetToL simply replaces it with
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// the provided constant value b.
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//
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// Example:
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//
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// type Config struct {
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// Debug bool
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// Timeout int
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// }
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//
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// debugLens := lens.MakeLens(
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// func(c Config) bool { return c.Debug },
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// func(c Config, d bool) Config { c.Debug = d; return c },
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// )
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//
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// result := F.Pipe1(
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// io.Of(Config{Debug: true, Timeout: 30}),
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// io.LetToL(debugLens, false),
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// ) // IO[Config{Debug: false, Timeout: 30}]
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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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) Operator[S, S] {
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return LetTo(lens.Set, b)
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}
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