The most commonly used functions/methods are the non-mutating versions, that newcomers to Julia do learn about first. (The exception being assigning values to v

The most commonly used functions/methods are the non-mutating versions, that newcomers to Julia do learn about first. (The exception being assigning values to vectors and dictionaries using `setindex!`, as in `vector[i] = x` or `dict[key] = value`.) A lot of user code just uses functional methods on types which have the potential to be mutated. OTOH, library methods that are called by the user often involves optimized code that might be doing mutation internally but presents a functional interface, such as `sort(vector)` (which basically uses `sort!(copy(vector))` internally).