Just a little snippet of code to remind me of the behaviour of constants in Julia

playing_with_constants.jl

const x = 1.0 ;

function foo(y)
    println("x = ", x)
end

foo("a string") # should print "x = 1.0"
# Invoking foo just JIT-compiled foo to use x = 1.0 if the argument is a string.

x = 2.0 ; # modify constant

foo("another string") # should print "x = 1.0" still
# because the argument is still a string, so no more compilation was done
# and foo used the previously compiled method for strings that thinks x = 1.0

foo(0) # should print "x = 2.0" this time
# because the argument is not a string this time, so a new JIT-compiled foo
# was used only this time with the updated x = 2.0 value

# Can I define the constants after the function?
# Let me change the order... with z undefined at this point
function baz(y)
    println("z = ", z)
end

baz("yet another string") # should raise an error

const z = "baz!" # Define z after the fact

baz("yet another string") # Now it should print "baz!"