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alleycats - Extract[F[_]] the only way to get the syntax is the deprecated one #4670

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alleycats - Extract[F[_]] the only way to get the syntax is the deprecated one #4670

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80527cf
Fixed issue #4642
aluscent Oct 29, 2024
992f72d
Added header to file
aluscent Oct 29, 2024
2c1d797
Formatted using scalafmt
aluscent Oct 29, 2024
b9b7e20
Changing ExtractOps class to value class
aluscent Nov 2, 2024
4bb630a
Made ExtractOps class a value class
aluscent Dec 3, 2024
843182c
Applied scalafmt on file
aluscent Dec 3, 2024
63bd760
Merge branch 'main' into alleycats-extract-syntax-unavailable
aluscent Dec 7, 2024
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2 changes: 1 addition & 1 deletion alleycats-core/src/main/scala/alleycats/syntax/all.scala
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Expand Up @@ -21,4 +21,4 @@

package alleycats.syntax

object all extends EmptySyntax with FoldableSyntax
object all extends EmptySyntax with FoldableSyntax with ExtractSyntax
33 changes: 33 additions & 0 deletions alleycats-core/src/main/scala/alleycats/syntax/extract.scala
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@@ -0,0 +1,33 @@
/*
* Copyright (c) 2015 Typelevel
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

package alleycats
package syntax

import alleycats.Extract

object extract extends ExtractSyntax

trait ExtractSyntax {
implicit class ExtractOps[F[_], A](fa: F[A])(implicit ev: Extract[F]) {
def extract(): A = ev.extract(fa)
}
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I wonder if it makes sense to convert it into a value class, e.g.:

Suggested change
implicit class ExtractOps[F[_], A](fa: F[A])(implicit ev: Extract[F]) {
def extract(): A = ev.extract(fa)
}
implicit final class ExtractOps[F[_], A](private val fa: F[A]) extends AnyVal {
def extract(implicit ev: Extract[F]): A = ev.extract(fa)
}

The reason why I think it could make sense is that

  1. This is a pretty valid use case for value classes in general and allows to save on memory allocations a little bit.

  2. Newer syntaxes in Cats-core use this approach a lot, see Applicative syntax for example:

    cats/core/src/main/scala/cats/syntax/applicative.scala

    Lines 37 to 56 in 769bf21

    final class ApplicativeIdOps[A](private val a: A) extends AnyVal {
    def pure[F[_]](implicit F: Applicative[F]): F[A] = F.pure(a)
    }
    @deprecated("Use by-value or by-name version", "2.8.0")
    final class ApplicativeOps[F[_], A](private val fa: F[A]) extends AnyVal {
    def replicateA(n: Int)(implicit F: Applicative[F]): F[List[A]] = F.replicateA(n, fa)
    def unlessA(cond: Boolean)(implicit F: Applicative[F]): F[Unit] = F.unlessA(cond)(fa)
    def whenA(cond: Boolean)(implicit F: Applicative[F]): F[Unit] = F.whenA(cond)(fa)
    }
    final class ApplicativeByValueOps[F[_], A](private val fa: F[A]) extends AnyVal {
    def replicateA(n: Int)(implicit F: Applicative[F]): F[List[A]] = F.replicateA(n, fa)
    def replicateA_(n: Int)(implicit F: Applicative[F]): F[Unit] = F.replicateA_(n, fa)
    }
    final class ApplicativeByNameOps[F[_], A](private val fa: () => F[A]) extends AnyVal {
    def unlessA(cond: Boolean)(implicit F: Applicative[F]): F[Unit] = F.unlessA(cond)(fa())
    def whenA(cond: Boolean)(implicit F: Applicative[F]): F[Unit] = F.whenA(cond)(fa())
    }

}