`maybe` is a common prefix for functions that may or may not do something, eg:
https://github.com/elixir-lang/elixir/blob/779ccdb7564d587dfdadc1285a4dc57eb24768a1/lib/logger/lib/logger.ex#L1074 https://github.com/elixir-lang/elixir/blob/779ccdb7564d587dfdadc1285a4dc57eb24768a1/lib/elixir/lib/file.ex#L1796 And so on... So I'd propose to call it `maybe_run`, just `maybe`, or something with `maybe`. On Friday, June 5, 2020 at 9:48:56 AM UTC-4, Adam Lancaster wrote: > > We have something similar in our code base we called the Maybe.Pipe: ~> > > > On 5 Jun 2020, at 14:41, Piotr Szmielew <p.sz...@ava.waw.pl <javascript:>> > wrote: > > maybe it should be called run_if? so, something like this: > > defmacro run_if(piped_value, condition, fun) do > quote do > if unquote(condition) do > unquote(fun).(unquote(piped_value)) > else > unquote(piped_value) > end > end > end > > and then used as: > > %{a: 1, b: 2} > |> X.run_if(1 == 2, &Map.put(&1, :foo, "foo")) > |> X.run_if(1 == 1, &Map.put(&1, :foo, "bar")) > # => %{a: 1, b: 2, foo: "bar"} > > On Fri, Jun 5, 2020 at 3:27 PM José Valim <jose...@dashbit.co > <javascript:>> wrote: > >> Hi Riccardo, >> >> This is an interesting proposal! Unfortunately if the value you want to >> compute is expensive, then you need to fallback to the usual `if` approach. >> This is also specific to maps. It may be worth considering a more general >> purpose mechanism, for example: >> >> map >> |> update_if(foo != nil, &Map.put(&1, :foo, foo)) >> |> update_if(bar != nil, &Map.put(&1, :bar, normalize_bar(bar))) >> >> Being in Kernel also allows us to write it as a macro, which can be >> further optimized. Not sure if update_if is the best name though. >> Suggestions and comparisons to other languages are welcome. >> >> On Fri, Jun 5, 2020 at 12:36 PM Riccardo Binetti <rb...@gmx.com >> <javascript:>> wrote: >> >>> Hi everybody, >>> >>> this is my first proposal so I hope I get the format right, I've already >>> checked in the mailing list and I haven't found similar proposals. >>> >>> *Problem* >>> >>> When manually constructing a map using external options or the result of >>> a pattern match on a struct, I often find myself in the situation where I >>> have to add a value only if it is non-nil. >>> >>> The possible approaches available today are these >>> >>> >>> *Using if* >>> >>> >>> def some_fun(s) do >>> MyStruct{ >>> foo: foo, >>> bar: bar, >>> baz: baz >>> } = s >>> >>> map = %{a: "hello", b: 42} >>> >>> map = >>> if foo do >>> Map.put(map, :foo, foo) >>> else >>> map >>> end >>> >>> map = >>> if bar do >>> Map.put(map, :bar, bar) >>> else >>> map >>> end >>> >>> if bar do >>> Map.put(map, :baz, baz) >>> else >>> map >>> end >>> end >>> >>> >>> This is the obvious solution, but it gets very verbose very quickly >>> >>> >>> *Populating the map and then filtering* >>> >>> def some_fun(s) do >>> MyStruct{ >>> foo: foo, >>> bar: bar, >>> baz: baz >>> } = s >>> >>> %{a: "hello", b: 42} >>> |> Map.put(:foo, foo) >>> |> Map.put(:bar, bar) >>> |> Map.put(:baz, baz) >>> |> Enum.filter(fn {_k, v} -> v end) >>> |> Enum.into(%{}) >>> end >>> >>> This is more concise, but it creates intermediate maps that are >>> immediately thrown away. Moreover, if the initial map is very large, the >>> filter operation is expensive since it traverses the whole map. >>> >>> >>> *Implementing a maybe_put helper function* >>> >>> def some_fun(s) do >>> MyStruct{ >>> foo: foo, >>> bar: bar, >>> baz: baz >>> } = s >>> >>> %{a: "hello", b: 42} >>> |> maybe_put(:foo, foo) >>> |> maybe_put(:bar, bar) >>> |> maybe_put(:baz, baz) >>> end >>> >>> defp maybe_put(map, _key, nil), do: map >>> defp maybe_put(map, key, value), do: Map.put(map, key, value) >>> >>> This is the solution I end implementing almost always. It is present in >>> multiple modules across the codebase I work on (and/or put in a generic >>> Utils module), and talking with my colleagues I found out that is a utility >>> function that they also have to implement often and it has turned up at >>> least a couple times[1][2] also in the Elixir Forum. >>> >>> [1] >>> https://elixirforum.com/t/elixir-way-to-conditionally-update-a-map/17952/21?u=rbino >>> [2] >>> https://elixirforum.com/t/is-there-way-to-create-map-and-conditionally-exclude-some-keys/23315/5?u=rbino >>> >>> This brings me to my proposal, which is a more generic version of >>> maybe_put. >>> >>> *Proposal* >>> >>> Add Map.put_if/4 to the Map module. This is more generic (and imho >>> clearer) than maybe_put and can be used to solve the same problem without >>> creating intermediate results and allowing the code to be clear and concise. >>> >>> >>> def some_fun(s) do >>> MyStruct{ >>> foo: foo, >>> bar: bar, >>> baz: baz >>> } = s >>> >>> %{a: "hello", b: 42} >>> |> Map.put_if(:foo, foo, foo != nil) >>> |> Map.put_if(:bar, bar, bar != nil) >>> |> Map.put_if(:baz, baz, baz != nil) >>> end >>> >>> Let me know if you need any other information. >>> -- >>> Riccardo >>> >>> -- >>> 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-l...@googlegroups.com <javascript:>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/elixir-lang-core/f513b901-fd93-4f28-88a2-f496a3c84a21o%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/elixir-lang-core/f513b901-fd93-4f28-88a2-f496a3c84a21o%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-l...@googlegroups.com <javascript:>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4K_QVpD-eRG6JUOMYV5pVTLchpTgbO0fqN6pPCmuSL4NA%40mail.gmail.com >> >> <https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4K_QVpD-eRG6JUOMYV5pVTLchpTgbO0fqN6pPCmuSL4NA%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-l...@googlegroups.com <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/CANmTJ6thcegKJjb7aKPhtQoqfo5%3DCgJo2-KnORRg8B2UcEB%3D-A%40mail.gmail.com > > <https://groups.google.com/d/msgid/elixir-lang-core/CANmTJ6thcegKJjb7aKPhtQoqfo5%3DCgJo2-KnORRg8B2UcEB%3D-A%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. 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