Given Dialyzer does not natively support stepped ranges, I don't think we should emulate them and have 1..10//1 and 1..10//2 to two very distinct things. :(
On Tue, Apr 13, 2021 at 5:03 PM [email protected] <[email protected]> wrote: > While working with the v1.12.0 rc0 release, I wrote the following typespec: > > @spec my_fun(1..10//2) :: boolean() > > which resulted in the following error: > > == Compilation error in file lib/foobar.ex == > ** (CompileError) lib/foobar.ex:6: type ..///3 undefined (no such type in > Foobar) > > My confusion stemmed from my belief that ranges in typespecs were > interpreted by Elixir and expanded at compile time (e.g. 1..10 to > 1|2|3|4|5|...) since the syntax (first..last) matches the Elixir range > syntax and Erlang has no native ranges. Of course, this was wrong because > while Erlang doesn't have ranges, *Dialyzer* does. > > While I can't think of the last time I wanted the contract of my function > to be "only accepts odd integers between 1 and 100", it also seems like a > curious omission. From the perspective of someone with good knowledge of > Elixir but limited knowledge of Erlang and Dialyzer, I had originally > believed that this was some kind of mistake or oversight. > > There also might be a use-case in providing additional information to > Dialyzer, such as: > @spec odd?(1..10//2) :: true > @spec odd?(2..10//2) :: false > > Would it be worth taking a type such as 1..10//2 and compiling it to > 1|3|5|7|9 for Dialyzer? > > -- > 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 [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/d9415490-4285-48fe-a863-4d778ccc962an%40googlegroups.com > <https://groups.google.com/d/msgid/elixir-lang-core/d9415490-4285-48fe-a863-4d778ccc962an%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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4LLVF4px9J2-3oh_Oirdpa-6YB_JQZ_D%2BxrunQ1%3D-g_jQ%40mail.gmail.com.
