Aetherus

Aetherus

Why is `Kernel.then/2` defined as a macro?

Just out of curiosity. Why is Kernel.then/2 a macro instead of a normal function?

Here’s the source code of Kernel.then/2:

defmacro then(value, fun) do
  quote do
    unquote(fun).(unquote(value))
  end
end

Here’s what I thought what the source code of Kernel.then/2 could be:

def then(value, fun) do
  fun.(value)
end

Marked As Solved

benwilson512

benwilson512

Author of Craft GraphQL APIs in Elixir with Absinthe

To be a comparable case you need to use theni from another module. As I recall inlining can work differently depending on whether you are inlining a function within the same module or from another module.

Also Liked

adamu

adamu

Check out the pull request that did it. It includes reasons and a link to a mailing list discussion, too.

Aetherus

Aetherus

You are absolutely correct. Thank you.

When I put the callers and the callees into different modules, theni/2 generates the same instructions as thenf/2.

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