[julia-users] Scanning the optional arguments of a function

[Dominique Orban]

I'm writing a function that takes optional arguments. Many of them must be 
arrays of a certain size. I'd like to perform a quick check of their size 
at the top of the function and thought it would be a good use case for meta 
programming, but I can't seem to get the syntax right. Here's an example 
that hopefully illustrates what I'm trying to do:

function test(a; x=zeros(5), y=zeros(5))
  for arg in {:x, :y}
    if length(eval(arg)) != 5  # ERROR: x not defined
      error(@eval $(string(arg, " must have length 5")))
    end
  end
  # ...
end

I tried *@eval $(arg)* in the argument to *length*, but without success. 
Line 3 always causes "ERROR: x not defined" to be raised.

Thanks!