For all my experience with the try-catch paradigm, I've never seen a situation where I wanted a name error in the try block to be caught. It's hard to imagine one. A name error is a typo 99% of the time, and a mistake 99% of the remainder. Catching it accidentally can lead to an especially frustrating debugging experience.

So why do all the dynamic languages have catch statements catch name errors by default?

Unlike Julia and Javascript, Python and Ruby have real exception hierarchy systems and allow multiple catch clauses that catch different kinds. But both of them still include name errors in a bare catch.

And their designers obviously realized that there are some exceptions you don't usually want to catch, as they have a class you can catch that excludes other things in that category (like KeyboardInterrupts): StandardError in Ruby, Exception in Python (with BaseException being the real progenitor). But for some reason both of them consider NameError a subclass of this!

Why do they do all this? And are there dynamic languages that don't?



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