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Modified documentation to FilterWithPrevious #3708

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Modified documentation to FilterWithPrevious
ankitkumarrain Apr 5, 2026
67fb11f
changed the docs according to recommendation
ankitkumarrain Apr 10, 2026
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11 changes: 7 additions & 4 deletions core/shared/src/main/scala/fs2/Stream.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1040,17 +1040,18 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
underlying.flatMapOutput(evalOut).streamNoScope
}

/** Like `evalMap`, but operates on chunks for performance. This means this operator
* is not lazy on every single element, rather on the chunks.
/** Like `evalMap`, but operates on chunks for performance. Evaluates `f` for all elements
* within a chunk using the Applicative instance, which allows parallel evaluation if supported by `F`.
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@mpilquist mpilquist Apr 10, 2026

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Recommend removing "using the Applicative instance, which allows ...". Feels out of place here.

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@ankitkumarrain ankitkumarrain Apr 10, 2026 •
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Hey @mpilquist, thank you for your suggestions. I’ve updated the changes accordingly. Could you please take another look?

*
* For instance, `evalMap` would only print twice in the follow example (note the `take(2)`):
* This operator is not lazy on individual elements, only on chunks. For instance, `evalMap` would
* only print twice in the following example (note the `take(2)`):
* @example {{{
* scala> import cats.effect.SyncIO
* scala> Stream(1,2,3,4).evalMap(i => SyncIO(println(i))).take(2).compile.drain.unsafeRunSync()
* res0: Unit = ()
* }}}
*
* But with `evalMapChunk`, it will print 4 times:
* But with `evalMapChunk`, it will print 4 times (entire first chunk is processed):
* @example {{{
* scala> Stream(1,2,3,4).evalMapChunk(i => SyncIO(println(i))).take(2).compile.drain.unsafeRunSync()
* res0: Unit = ()
Expand Down Expand Up @@ -1233,6 +1234,8 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
/** Like `filter`, but the predicate `f` depends on the previously emitted and
* current elements.
*
* The first element is always emitted (no previous element to compare).
*
* @example {{{
* scala> Stream(1, 9, 5, 6, 7, 8, 9, 10).filterWithPrevious((previous, current) => previous < current).toList
* res0: List[Int] = List(1, 9, 10)
Expand Down