What is the alternative to the erlang -define syntax

Questions / Help
1

Hi Everyone,

I know we can bind variable using
@ at the global level
I am trying to bind this example but in elixir how ?
-define(INT, 32/big-signed-integer).
I tried
@int 32-big-signed-integer,
but it doesn’t work, anyone can help me please

Thanks

2

You can’t do this as an attribute, as the attribute would try to evaluate at compiletime to 32 divided by the value of big-signed-integer. which is probably not defined.

So with a bit of luck you might be able to write a macro that works for you, something like

defmacro i32() do
  quote do: 32/big-signed-integer
end
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3

Hey @NobbZ

I believe the marco is always the best tweak

Thank you very much

4

@NobbZ

how we can create a marco to simulate the “<=” BitstringPattern <= BitStringExpr.
in elixir ?

http://erlang.org/doc/reference_manual/expressions.html

This is good when doing a pattern matching on long bitstring, for example
[ {key, value} || <<key::size, value::size>> <= <<map_buffer>>]
this is kinda a mix between For loop and bitstring patternmatching.
this could be done in erlang, but in elixir I had to implement a very long logic to do so
any idea how ?

Thanks

1 Like
5

Perhaps this is what you are looking for?

for <<key::size, value::size <- map_buffer>>, do: {key, value}

See bitstring generators under:

https://elixir-lang.org/getting-started/comprehensions.html

3 Likes
6

Wow @cmkarlsson,
This is exactly what I am looking for,
you just saved my day
going to implement it now.
Thank you very much.

2 Likes