I just want to confirm what has already been mentioned a number of times in this thread: the reason for not having static typing in Erlang was the absolute need for doing dynamic code upgrades of running systems. This was an absolute requirement and if we couldn’t do it then our language/system wasn’t interesting. There aren’t many systems using it today as most try to do rolling upgrades but we didn’t have that option back then so we had to be able to upgrade a running system. Remember we are talking late 80’s early 90’s here.
Some evil tongues says it because we didn’t know how to write type-checking systems but that is totally ridiculous. As we had taught ourselves to write compilers, and done a number of them, to implement virtual machines, and done a number of them, and to implement run-time and os-like systems, and done a number of them as well, then implementing type-checking would not have been especially difficult. It’s not rocket science and it wasn’t then either. Just RTFM.
Whether you like dynamic typing or prefer static typing that is a matter of choice but as I have said for us it was not an option.
On a side note I would say probably the main difficulty with implementing a statically typed language on top of erlang/OTP/BEAM is interfacing to the world outside. I mean you can call any function with any arguments and send any message to any process so the problem how do I make the statically typed part of the system “safe”. And no, processes can’t hide either as with the Process.list/processes built-in functions I can see all processes.
A final note: Erlang/elixir/BEAM is actually strongly typed but dynamically typed not statically typed. If we want to be picky.
