MapSets are *very* useful constant time data structures; and I keep on finding myself wishing there was a future-proof approved way to use them in guards. Consider this my +1.
I believe eksperimental's original rationale still holds: 1. :erlang.is_map_key/2, as well as :erlang.map_get/2, are awkward to use guards (as of writing, by design, to encourage destructuring) 2. a MapSet's .map is a private field and should not be accessed/destructured directly (see: various pain points when the internal implementation of Range fields changed) I'd like to re-open a proposal for a guard-safe MapSet.is_member/2, with the implementation: defmodule MapSet do defguard is_member(map_set, value) when is_struct(map_set, __MODULE__) and :erlang.is_map_key(value, map_set.map) end This would bring the core conceit of MapSets (constant-time set membership) into where they are very valuable (constant-time guard operations for pattern matching against function heads). I am not convinced that deprecating MapSet.member?/2 adds much value if it would force developers to require MapSet before using its core functionality, so I'm content having a bit of duplication. Similarly, checking the size of a MapSet is less core to its utility, and again I wouldn't want to developers to have to require the module just to check the size—so I'm proposing that addition. Just the single guard! On Thursday, December 24, 2020 at 1:37:40 AM UTC-6 José Valim wrote: > Because if I have a MapSet, I would prefer to call MapSet API to make the > intent clearer. > > On Thu, Dec 24, 2020 at 4:48 AM eksperimental <eksper...@autistici.org> > wrote: > >> On Mon, 21 Dec 2020 22:37:53 -0500 >> eksperimental <eksper...@autistici.org> wrote: >> >> > Hi list, >> > I would like to propose to convert two existing functions to guards in >> > the MapSet module. >> > >> > 1. Is MapSet.size/1. I found myself not being able to use this >> > function in guards, and having to port my code, unless I want to get >> > into the bad habit of reading the internal structure of the struct >> > which is an opaque type. >> > This guard can be implemented with :erlang.map_get/2 >> > >> > 2. Deprecate MapSet.member?/2 in favor of MapSet.is_member/2 >> > >> > Thank you for reading >> > >> >> Actually, why are we having MapSet.member?/2 when we have >> Enum.member?/2. It is redudant. >> >> -- >> 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-co...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/5fe40f76.1c69fb81.f8161.5ba3SMTPIN_ADDED_MISSING%40gmr-mx.google.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/93cec4b9-526c-48a9-9bb6-94c06c74827bn%40googlegroups.com.
