Julia and other mainstream programming languages handle arithmetic involving different number types so effortlessly that most of us likely don’t pay much attention to this fact:
julia> 3 + 4.2 #1 7.2 julia> UInt8(5) + Int128(3e6) #2 3000005 julia> 1//4 + 0.25 0.5
In reality, doing this involves quite a lot of complexity. Under the hood, most programming languages have defined a set of promotion rules, which say what should be done if you combine numbers of different types. Promotion rules make sure all the numbers are converted to a sensible common number type that can be used in the final calculation. Don’t confuse number conversion with parsing text strings to produce numbers.