DataFramesMeta’s macros are weird, because they want to behave like functions. @transform(df, y = 5), but they are still macros. If @transform were a function, it would be implemented like transform(df; kwargs...). Indeed, this is how the functions that @transform calls work. So I thought, in Data…

[image] pdeffebach: When you have a macro where everything is splatted, the collected expression includes everything between the parentheses. But when you have a multi-argument macro, where the second argument is splatted, the collected expression only goes until the first semi-colon. What’s …

All the kwargs get collected in the first argument x, all the rest gets collected in args. This is indeed a bit weird. Maybe worth opening an issue. But this couldn’t be changed until Julia 2.0.

[image] mauro3: But this couldn’t be changed until Julia 2.0. Not unless it is considered a bug, and the changes don’t break any registered package .

Thanks for the answer! dump((x, args...)) gets the first argument as the :parameters-annotated keyword arguments. I will admit that this is a bit of a pain. The relevant code to work with is here: function transform_helper(x, args...) quote $transform($x, $(map(args) do kw …

That I agree. It even had real consequences that I complained about. Unfortunately, changing this will be very breaking and I’m not sure if there can be a way to give a useful depwarn for macros…

Is there any way to leverage the way functions automatically parse this so I can avoid doing a bunch of => to = transitions and sorting through the syntax tree? Or is it all done in lisp?

Tangentially related, the way I’ve done keyword arguments with macros in the past is to have the macro create an expression that calls a proper keyword argument function which returns the ‘completed’ set of parameters. See tkoolen/LoopThrottle.jl/blob/3d90af9db9c14fc274f1d110948cef21d6ffa0b…

This is interesting, thanks! My use-case is probably something a bit more abstract, since we would just have kwargs... splatted and not know what they will be. It seems like a MacroKeywordArguments could be a useful package.

Weird macro behavior trying to simulate keyword arguments

General Usage

Tamas_Papp November 21, 2018, 9:24am 3

Not unless it is considered a bug, and the changes don’t break any registered package.

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Weird macro behavior trying to simulate keyword arguments

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