what is the point of heterogenous arrays?

Question

I know that more-dynamic-than-Java languages, like Python and Ruby, often allow you to place objects of mixed types in arrays, like so:

[\"hello\", 120, [\"w         


        

Answer 1

As katrielalex wrote: There is no reason not to support heterogeneous lists. In fact, disallowing it would require static typing, and we're back to that old debate. But let's refrain from doing so and instead answer the "why would you use that" part...

To be honest, it is not used that much -- if we make use of the exception in your last paragraph and choose a more liberal definition of "implement the same interface" than e.g. Java or C#. Nearly all of my iterable-crunching code expects all items to implement some interface. Of course it does, otheriwise it could do very little to it!

Don't get me wrong, there are absolutely valid use cases - there's rarely a good reason to write a whole class for containing some data (and even if you add some callables, functional programming sometimes comes to the rescue). A dict would be a more common choice though, and namedtuple is very neat as well. But they are less common than you seem to think, and they are used with thought and discipline, not for cowboy coding.

(Also, you "User as nested list" example is not a good one - since the inner lists are fixed-sized, you better use tuples and that makes it valid even in Haskell (type would be [(String, Integer)]))