[erlang-questions] Guards syntax for multiple values

Fred Hebert mononcqc@REDACTED
Mon Mar 25 20:35:39 CET 2019

On Mon, Mar 25, 2019 at 2:03 PM Jesper Louis Andersen <
jesper.louis.andersen@REDACTED> wrote:

> Thinking out loud, I think it might be beneficial to look at two additions:
> lists:member - because length(..) is in the set of Valid GuardSeqs and is
> O(n)
> maps:is_key
> maps:get
> The latter map variants are arguably even stronger since they have good
> lookup time, even for very large maps. Writing maps:is_key(X, #{ a => true,
> b => true }) should be fast and since it is a literal, it can be optimized
> in a number of ways by the compiler.
OTP-21 includes the new BIFs erlang:map_get(Key, Map) and
erlang:map_size(Map) for these reasons. Only lists:member is missing.
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