Functions and multiple return values

You define a function with function name(a, b) ... end, and it's best to put local before it, just as you do with variables. A function hands back its result with return, and in Lua you can return more than one value, as in return newHp, healed. The caller receives them like this: local hp, healed = heal(90), with no table or object needed to bundle them.

Lua doesn't let you write default values in the line that defines the function. An argument that wasn't passed arrives as nil, so you write amount = amount or 25 at the top of the function. This is safe with zero, because zero counts as true in Lua.

But this approach fails with booleans: loud = loud or true always sets loud to true, even when the caller passes false explicitly, so for those you write if loud == nil then loud = true end. And remember that local hp = heal(90) takes only the first value and drops the rest without any error.