This is most likely not the right place to use eval!
You need to define your problem better. What you describe here doesn't need
a macro whatsoever.
Macros are for manipulating the syntax tree, which is why the arguments are
not the values, but expressions.
What a macro is intended to do is more something like this:
macro testmacro(N)
quote
for i = 1:$N
println("Hello!")
end
end
end
n = 10
@testmacro n
So all the code inside a macro should be used to transform an expression,
which than replaces the original expression that you gave the macro via its
arguments
Am Mittwoch, 11. März 2015 13:37:55 UTC+1 schrieb Kaj Wiik:
>
> I have a problem in using variables as argument for macros. Consider a
> simple macro:
>
> macro testmacro(N)
> for i = 1:N
> println("Hello!")
> end
> end
>
> @testmacro 2
>
> Hello!
> Hello!
>
>
> So, all is good. But if I use a variable as an argument,
>
> n = 2
> @testmacro n
>
>
> I get an (understandable) error message "ERROR: `colon` has no method
> matching colon(::Int64, ::Symbol)".
>
> Is this the correct place to use eval() in macros, like
>
> macro testmacro(N)
> for i = 1:eval(N)
> println("Hello!")
> end
> end
>
> This seems to work as expected. I tried multitude of combinations of
> dollar signs, esc, quotes and brackets, none of them worked :-), got
> "ERROR: error compiling anonymous: syntax: prefix $ in non-quoted
> expression"...
>
> Are there better ways to do this, is it OK to use eval() in this context?
>
> Thanks,
> Kaj
>
>
