Transforming funs to match specifications

There is no way to have ets:fun2ms/1 in Elixir, as Elixir disallows parse transforms. However you can use macros to achieve the same thing.

There is this old post…

Maybe this package can help?

There is also @ityonemo’s

https://github.com/E-xyza/match_spec

:ets matchspec helper library for elixir. Exposes the fun2ms/1 macro which transforms elixir-style function code into ets matchspecs.

iex> require MatchSpec
iex> MatchSpec.fun2ms(fn {key, value} when key === :foo -> value end)
[{{:"$1", :"$2"}, [{:"=:=", :"$1", {:const, :foo}}], [:"$2"]}]

fun2ms and ms2fun for elixir! Advent of code day 22 (remastered)

Thanks for the suggestions. Why does the Elixir compiler disallow parse transforms?

The problm is I have another issue than just doing it from Elixir and that is I want to do it from LFE (Lisp Flavoured Erlang) as well. And there I have records which Elixir doesn’t, and these 2 packages, don’t really support. The LFE compiler makes full use of the Erlang compiler so it just translates all record operations into the record expressions in the Erlang AST.

I am also looking at doing it in a nice way using the modules in Erlang but without parse transforms, which will be the last option.

Here is discussion

https://github.com/elixir-lang/elixir/issues/5762

Writing such macro also shouldn’t be really hard there, so it can go that route.