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Add discard method as a safer alternative to void #1001

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merged 5 commits into from
Aug 29, 2022
Merged

Add discard method as a safer alternative to void #1001

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4294484
add discard method;
evo-funfunfine Aug 29, 2022
3ddbb2a
bring back accidentally deleted file;
evo-funfunfine Aug 29, 2022
f7c3f85
fix typos in scaladoc;
evo-funfunfine Aug 29, 2022
032d951
fix typos in scaladoc;
evo-funfunfine Aug 29, 2022
c820a1b
add small spec for monadic.discard;
evo-funfunfine Aug 29, 2022
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16 changes: 16 additions & 0 deletions modules/higherKindCore/src/main/scala/tofu/syntax/monadic.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,22 @@ object monadic extends TupleSemigroupalSyntax with ApplicativeSyntax with MonadS
def unit[F[_]](implicit F: Applicative[F]): F[Unit] = F.unit

implicit final class TofuFunctorOps[F[_], A](private val fa: F[A]) extends AnyVal {
/** Safer way than [[void]] to discard a value
*
* Explicit type ascription eliminates a bug when one can begin discarding non-discard-able value.
*
* @example
* {{{
* val computation1: F[Thing] = ???
* val result11: F[Unit] = computation1.void
* val result12: F[Unit] = computation1.discard[Thing]
*
* //after changes or refactoring
* val computation2: F[F[Thing]] = ???
* val result21: F[Unit] = computation2.void //error here, nested F is not evaluated and compiler doesn't warn
* val result22: F[Unit] = computation2.discard[Thing] //compiler produces an error
* }}} */
def discard[AA](implicit ev: AA =:= A, F: Functor[F]): F[Unit] = F.void(fa)
def map[B](f: A => B)(implicit F: Functor[F]): F[B] = F.map(fa)(f)
def fmap[B](f: A => B)(implicit F: Functor[F]): F[B] = F.fmap(fa)(f)
def widen[B >: A](implicit F: Functor[F]): F[B] = F.widen(fa)
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