Julia motivation: why weren't Numpy, Scipy, Numba, good enough?

Yes. C++ overloading is multi-argument but is also all static — it only works on types known to the compiler. If you want dynamic dispatch, you need to use virtual methods, which dispatch on a single argument and use different syntax. Dynamic dispatch appears to be important. People want to just throw whatever they have at some functions, and have the right thing happen, regardless of whether the code can be statically typed. But in C++ static type errors are not even the worst of it: the compiler will pick an overload to call based on whatever type it can determine, which can be different from the run-time type. That doesn’t seem to be a huge problem in practice, but it’s very unsatisfying. Only the ground truth of what an object actually is should matter, not compiler limitations.

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