[fusiongyro]

One thing that makes Julia cool is that adding the types improves performance, but you don't have to add them if you don't want to.

[dnautics]

Adding types in julia usually does not improve performance for function definitions... it may improve performance for collections (like specifying the type that an array collects), but usually julia is pretty darn good at correctly inferring the collection type

[ummonk]

Right. Adding types is a good way to ensure you're writing type-stable code, but when you do write type-stable code, Julia can usually infer that it is type-stable without needing actual specified types.