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79 lines
2.6 KiB
Go
79 lines
2.6 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 array
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import (
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"github.com/IBM/fp-go/v2/internal/array"
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)
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// Traverse maps each element of an array to an effect (HKT), then collects the results
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// into an effect of an array. This is like a combination of Map and Sequence.
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//
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// Unlike Sequence which works with []HKT<A> -> HKT<[]A>, Traverse works with
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// []A -> (A -> HKT<B>) -> HKT<[]B>, allowing you to transform elements while sequencing effects.
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//
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// Type parameters:
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// - HKTB = HKT<B> (e.g., Option[B], Either[E, B])
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// - HKTAB = HKT<func(B)[]B> (intermediate type for applicative)
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// - HKTRB = HKT<[]B> (e.g., Option[[]B], Either[E, []B])
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//
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// Example:
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//
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// import (
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// "github.com/IBM/fp-go/v2/option"
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// "strconv"
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// )
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//
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// // Parse strings to ints, returning None if any parse fails
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// parseAll := array.Traverse(
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// option.Of[[]int],
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// option.Map[[]int, func(int) []int],
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// option.Ap[[]int, int],
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// func(s string) option.Option[int] {
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// if n, err := strconv.Atoi(s); err == nil {
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// return option.Some(n)
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// }
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// return option.None[int]()
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// },
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// )
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//
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// result := parseAll([]string{"1", "2", "3"}) // Some([1, 2, 3])
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// result2 := parseAll([]string{"1", "x", "3"}) // None
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func Traverse[A, B, HKTB, HKTAB, HKTRB any](
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fof func([]B) HKTRB,
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fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
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fap func(HKTB) func(HKTAB) HKTRB,
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f func(A) HKTB) func([]A) HKTRB {
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return array.Traverse[[]A](fof, fmap, fap, f)
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}
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// MonadTraverse is the monadic version of Traverse that takes the array as a parameter.
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// It maps each element of an array to an effect (HKT), then collects the results
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// into an effect of an array.
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//
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// This is useful when you want to apply the traverse operation directly without currying.
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func MonadTraverse[A, B, HKTB, HKTAB, HKTRB any](
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fof func([]B) HKTRB,
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fmap func(func([]B) func(B) []B) func(HKTRB) HKTAB,
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fap func(HKTB) func(HKTAB) HKTRB,
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ta []A,
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f func(A) HKTB) HKTRB {
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return array.MonadTraverse(fof, fmap, fap, ta, f)
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}
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