We're missing your `decompose_function` so I couldn't run it, but from the
last time I worked with function-definition macros, I believe the correct
way to write it should be to add `esc` to the arguments so that it doesn't
apply hygiene, this way:
function $(esc(f))($(map(esc, args)...))
Unfortunately, last I checked there was a bug in Julia that prevented this,
and instead I have to cancel hygiene on the whole expression (and use
`gensym` where appropriate)
esc(:(function $f($(args...))
...)
Does that solve your issue?
On Monday, January 18, 2016 at 2:33:00 PM UTC-5, Julia Tylors wrote:
>
> #####################
> #IMPLEMENTATION CODE:
> #####################
>
> module Y
> export modify
>
> """
> A LOT OF CODE HERE, REMOVED FOR SIMPLICITY
> """
>
> function _modify(expr)
> is_lambda,f,args,body = decompose_function(expr)
> if is_lambda
> quote
> ($(args...)) -> $(transform(body))
> end
> else
> quote
> function $(esc(f))($(args...))
> $(transform(body))
> end
> end
> end
> end
>
> macro modify(func)
> _modify(func)
> end
> end
>
> #####################
> #USAGE CODE:
> #####################
>
> module X
> using Y
> type Arg{T}
> x::T
> end
> println(macroexpand( quote
> @modify function f(x::Arg{Bool})
> y = 12
> if x
> y+1
> else
> y-1
> end
> end
> end))
> end
>
> #####################
> #GENERATED CODE:
> #####################
>
> begin
> begin
> function f(#22#x::Y.Arg{Y.Bool})
> begin
> #21#y = 12 #
> begin
> "LOTS OF CODE HERE"
> end
> end
> end
> end
> end
>
> #########################
> #QUESTION
> #########################
>
> In the generated code, the argument Arg{Bool} is treated as if it is an
> element of module Y, but it is an element of module Y. So when the code
> executes, the interpreter complains and says:
> ERROR: LoadError: UndefVarError: Arg not defined
>
> Why $(args...) in the implementation code doesn't work?
>
> Thanks
>
>
>
