On Thursday, June 6, 2013 2:29:02 AM UTC-7, Steven D'Aprano wrote: > On Thu, 06 Jun 2013 12:29:44 +1000, Chris Angelico wrote: > > > > > On Thu, Jun 6, 2013 at 11:56 AM, Steven D'Aprano > > > <steve+comp.lang.pyt...@pearwood.info> wrote: > > >> On Wed, 05 Jun 2013 14:59:31 -0700, Russ P. wrote: > > >>> As for Python, my experience with it is that, as your application > > >>> grows, you start getting confused about what the argument types are or > > >>> are supposed to be. > > >> > > >> Whereas people never get confused about the arguments in static typed > > >> languages? > > >> > > >> The only difference is whether the compiler tells you that you've > > >> passed the wrong type, or your unit test tells you that you've passed > > >> the wrong type. What, you don't have unit tests? Then how do you know > > >> that the code does the right thing when passed data of the right type? > > >> Adding an extra couple of unit tests is not that big a burden. > > > > > > The valid type(s) for an argument can be divided into two categories: > > > Those the compiler can check for, and those the compiler can't check > > > for. Some languages have more in the first category than others, but > > > what compiler can prove that a string is an > > > HTML-special-characters-escaped string? In a very few languages, the > > > compiler can insist that an integer be between 7 and 30, but there'll > > > always be some things you can't demonstrate with a function signature. > > > > > > That said, though, I do like being able to make at least *some* > > > declaration there. It helps catch certain types of error. > > > > *shrug* > > > > I don't terribly miss type declarations. Function argument declarations > > are a bit simpler in Pascal, compared to Python: > > > > > > Function Add(A, B : Integer) : Integer; > > Begin > > Add := A + B; > > End; > > > > > > versus > > > > > > def add(a, b): > > if not (isinstance(a, int) and isinstance(b, int)): > > raise TypeError > > return a + b >
Scala also has isInstanceOf[Type] which allows you to do this sort of thing, but of course it would be considered terrible style in Scala. > > > > but not that much simpler. And while Python can trivially support > > multiple types, Pascal cannot. (Some other static typed languages may.) > > > > Whatever benefit there is in declaring the type of a function is lost due > > to the inability to duck-type or program to an interface. There's no type > > that says "any object with a 'next' method", for example. And having to > > declare local variables is a PITA with little benefit. > > > > Give me a language with type inference, and a nice, easy way to keep duck- > > typing, and I'll reconsider. But until then, I don't believe the benefit > > of static types comes even close to paying for the extra effort. Scala has type inference. For example, you can write val x = 1 and the compiler figures out that x is an integer. Scala also has something called structural typing, which I think is more or less equivalent to "duck typing," although I don't think it is used very often. Are you ready to try Scala yet? 8-) -- http://mail.python.org/mailman/listinfo/python-list
