In the official documentary, a macro example is provided: macro time(ex) return quote local t0 = time() local val = $ex local t1 = time() println("elapsed time: ", t1-t0, " seconds") val end end After this macro, a problem is immediately brought up: …

Please finish reading that page of doc.

I finished the page before I asked. I know that the way out is to use esc, but I still don’t understand why ex should be resolved in macro defining environment. If I do module MyModule import Base.@time myfun() = ... # compute something @time myfun() end then myfun is not even defined in macro d…

[image] Chong_Wang: then myfun is not even defined in macro defining environment. Right? What’s the problem? The base one should have the correct behavior and resolve to your function. The first example in the hygiene section is just demonstrating the problem and it is corrected a few lines l…

[image] yuyichao: at’s the problem? The base one should have the correct behavior and resolve to your function. The first example in the hygiene section is just demonstrating the problem and it is corrected a few lines later. Does this mean macro arguments should always be escaped?

Not always but yes when you want them to be treated as normal code.

Can you give me an example when escape is not needed in defining macros? I cannot come up with even one example where macro arguments should not be resolved in macro calling environment. Here comes another question: If macro arguments should almost always be escaped, why doesn’t the parser use …

[image] Chong_Wang: Can you give me an example when escape is not needed in defining macros? I cannot come up with even one example where macro arguments should not be resolved in macro calling environment. Anything that deconstruct the expression passed in. Or does not treat the input as nor…

Thank you for your explanation. @yuyichao

And interpolate in any local variables and functions

How is macro arguments resolved?

General Usage

cstjean August 9, 2017, 6:28pm 10

It’s also possible to just escape everything and use gensym to avoid name collisions.

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How is macro arguments resolved?

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