Guido van Rossum on Strong versus Weak Typing

Related link: http://www.artima.com/intv/strongweak.html

Artima.com has published Part V of an interview with Python creator Guido van Rossum, in which he talks about the robustness of systems built with strongly and weakly typed languages, the value of testing, and whether he'd fly on an all-Python plane.

Here's an excerpt:

Guido van Rossum: That attitude sounds like the classic thing I've always heard from strong-typing proponents. The one thing that troubles me is that all the focus is on the strong typing, as if once your program is type correct, it has no bugs left. Strong typing catches many bugs, but it also makes you focus too much on getting the types right and not enough on getting the rest of the program correct.

Strong typing is one reason that languages like C++ and Java require more finger typing. You have to declare all your variables and you have to do a lot of work just to make the compiler happy. An old saying from Unix developers goes something like, "If only your programs would be correct if you simply typed them three times." You'd gladly do that if typing your programs three times was enough to make them work correctly, but unfortunately it doesn't work that way.

All that attention to getting the types right doesn't necessarily mean you don't have other bugs in your program. A type is a narrow piece of information about your data. When you look at large programs that deal with a lot of strong typing, you see that many words are spent working around strong typing.