What is the correct syntax in metaprogramming assignment in Julia?

Question

I want x to take the value 4; why doesn't this work? What would the correct syntax be?

x=3
y=5

z=[:x; :y]

:(z[1])=4

Answer 1

The equivalent of &x in C++ in Julia, is to use a Ref.

x = Ref(1)
x[]     # get value of x, it's 1
x[] = 2 # set value of x to 2

What you want to do is

x = Ref(3)
y = Ref(5)
z = [x, y]
z[1][] = 4

For more information, see the section on Ref in the documentation.