Hey Macros are more than capable of providing this functionality, you'd just need to define your own `def` like macro that generates the desired function.
``` MyLib.def my_fun(my_var when my_var in [:foo, :bar]) ``` Cheers, Louis On Mon, 24 Sep 2018 at 20:01 Fernando Tapia Rico <fertap...@gmail.com> wrote: > IIRC, macros do not allow to abstract both the pattern match and the guard > within the same expression. For example, the Elixir codebase contains a > helper function that abstracts the pattern match, the guard and the "read" > function for dates and times separately. Here is the helper function > https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/calendar/iso.ex#L39-L70; > and here is an example of its usage > https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/calendar/datetime.ex#L522-L531 > . > > Besides, as described by José Valim in here > <https://github.com/elixir-lang/elixir/blob/master/lib/elixir/lib/calendar/iso.ex#L39-L70>, > internal guards would allow to write macros like: > > def my_fun(my_macro()) > > which would be expanded to: > > def my_fun(my_var when my_var in [:foo, :bar]) > > and rewritten by the Elixir compiler to: > > def my_fun(my_var) when my_var in [:foo, :bar] > > However, I'm not sure how common are those use cases 🤔. > > On Monday, September 24, 2018 at 8:22:07 PM UTC+2, Allen Madsen wrote: > >> If the goal were primarily macro usage, wouldn't this type of thing >> already be possible with a macro today? >> >> Allen Madsen >> http://www.allenmadsen.com >> >> >> On Mon, Sep 24, 2018 at 11:34 AM Christopher Keele <christ...@gmail.com> >> wrote: >> > That's a good point. I suspect the convention around manual usage would >>> converge around: >>> >>> *def foo(%{x: x} = result when x > 1), do: 1* >>> >>> which parses as expected. This version feels more natural to me. >>> >>> I don't think the other form would accidentally be introduced while >>> injecting one snippet of AST, because the tree would never be constructed >>> the wrong way. String-based expression interpolation might make that >>> mistake, but if you're metaprogramming with literal strings of code you've >>> already made a mistake. >>> >>> I hadn't typed out an assignment case with inline guards, it does feel >>> like it's doing too much in a short space with few grammar tokens to help >>> understand it. That's a good argument for intentionally discouraging these >>> constructs outside of metaprogramming, rather than adopting it as a common >>> usage language feature. >>> >>> -- >>> 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/f2fafacb-3302-4c03-9b1b-ed766a896cc2%40googlegroups.com >>> <https://groups.google.com/d/msgid/elixir-lang-core/f2fafacb-3302-4c03-9b1b-ed766a896cc2%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- > 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/7fda093f-03b5-4d1d-9c16-73c9475ca6a7%40googlegroups.com > <https://groups.google.com/d/msgid/elixir-lang-core/7fda093f-03b5-4d1d-9c16-73c9475ca6a7%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- 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/CABu8xFA4Eh_zuzbR2ykUzC7UXC%3DcK7NmuyLrXjH%3DgkFe8%2BJzYg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
