We should also address the fact that if we add Map.filter/2, we also likely have to add Map.drop/2 (to mimic Enum and Stream), but that name is already taken.
On Thu, 15 Aug 2019 at 12:26, Johanna Larsson <johanna.a.m.lars...@gmail.com> wrote: > The stream version is by far the slowest, which isn't surprising since > streams bring some overhead. Didn't measure memory usage though > https://gist.github.com/joladev/2b51260107078a1fc7f9d4504916fe21 > > Honestly, I tend to agree it would be nice to add it, for feature > completeness, even if it doesn't improve performance hugely. I understand > the desire to avoid unnecessary clutter in the core language, but this is a > core erlang function that we're explicitly not wrapping, when most of the > other ones are wrapped. And most likely just because it wasn't around from > the start. It's quite a bit more ergonomic to use `Map.filter` rather than > `for` or `map|>Enum.filter(pred)|>Enum.into({})`. Much cleaner. > > Not too hard to implement your own version of `Map.filter` though, so I > don't feel too strongly about it. > > On Thu, Aug 15, 2019 at 11:12 AM Alexei Sholik <alcosho...@gmail.com> > wrote: > >> The simplest alternative is to use :maps.filter(). It's not as easy to >> pipe into, but that's a minor concern for me. >> >> As another alternative, this should be faster and have lower memory >> footprint than using Enum, although you'd need to benchmark it as well to >> be sure: >> >> map >> |> Stream.filter(predicate) >> |> Map.new() >> >> Personally, I would love to see an extension for Map.new() that would >> allow filtering the first argument in addition to the currently supported >> transformation. So instead of the current >> >> Map.new(enumerable, fn thing -> {key, val} end) >> >> we could have >> >> Map.new(enumerable, map: fn thing -> {key, val} end, filter: fn {_key, >> val} -> predicate(val) end) >> >> Such an extension is unlikely to be added though because it would be >> another way of doing what is already possible with Enum, Stream, and Map. >> >> On Thu, Aug 15, 2019 at 10:29 AM Roman Smirnov <pom...@gmail.com> wrote: >> >>> Since OTP 18 there is a pretty convenient function :maps.filter >>> <http://erlang.org/doc/man/maps.html#filter-2>. >>> >>> I think it would be nice to have Map.filter(map, predicate) in Elixir >>> as well instead of doing >>> >>> >>> map|> Enum.filter(predicate)|> Enum.into(%{}) >>> >>> >>> or >>> >>> for {key, value} <- map, some_filter(key, value), into: %{}, do: {key, >>> value} >>> >>> The first one alternative is slower, b/c of 2-step transformation, and >>> the second one consume more memory, could not be piped and has a lack >>> of expressiveness (too imperative way to do a simple filtration). >>> There were benchmarks and a small discussion in PR: >>> https://github.com/elixir-lang/elixir/pull/9292, but the discussion >>> should be moved to this mailing list. >>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "elixir-lang-core" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to elixir-lang-core+unsubscr...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/5d403c4a-91f8-4c4d-8dc0-297185a2aed8%40googlegroups.com >>> <https://groups.google.com/d/msgid/elixir-lang-core/5d403c4a-91f8-4c4d-8dc0-297185a2aed8%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "elixir-lang-core" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to elixir-lang-core+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/CAAPY6eO5aDifRxHxv7QtD4%3Di_bYbUw1sphxMhq4jEjuR9naPSQ%40mail.gmail.com >> <https://groups.google.com/d/msgid/elixir-lang-core/CAAPY6eO5aDifRxHxv7QtD4%3Di_bYbUw1sphxMhq4jEjuR9naPSQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to elixir-lang-core+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/CAKL9qdTxQWdKDM7B%3D1XLkf7w9PeshpfSyrpsuhM%3DeaEqdZVSDA%40mail.gmail.com > <https://groups.google.com/d/msgid/elixir-lang-core/CAKL9qdTxQWdKDM7B%3D1XLkf7w9PeshpfSyrpsuhM%3DeaEqdZVSDA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- Andrea Leopardi an.leopa...@gmail.com -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAM9Rf%2BL54XitAyYbiztyr6BFqur_i4nVOcizrUn%2B1iebNwGo1A%40mail.gmail.com.
