Hands-On Design Patterns and Best Practices with Julia

Hiding a variable inside a global constant 

Before we conclude this section, there is yet another alternative to keep the flexibility of global variables while not losing too much performance. We can call it a global variable placeholder.

As it may have become clear to you by now, Julia can generate highly optimized code whenever the type of a variable is known at compilation time. Hence, one way to solve the problem is to create a constant placeholder and store a value inside the placeholder.

Consider this code:

# Initialize a constant Ref object with the value of 10const semi_constant = Ref(10)function add_using_global_semi_constant(x)    return x + semi_constant[]end

The global constant is assigned a Ref object. In Julia, a Ref object is ...