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March 03, 2004
A New Feature: Ask Phil
One of the things I've liked about Movable Type at UtahPolitics.org is the richer support for comments than I get with Radio. I've had comments enabled for a while on this site and sometimes I see the comments and sometimes I don't. Often I find a comment weeks after someone has posted it. In the spirit of experimentation, I've decided to disable Radio comments and use a more general purpose discussion board called Ask Phil (there's a permanent link on the left as well).
I realize that this is much different than comments in either Radio or Movable Type and that's why I consider it an experiment. At present, there's only one board which you can use for responding to something posted here, or asking me about anything else that you'd like. I encourage you to answer questions as well since we're much smarter collectively than any of us are individually. Later I might create a forum for the CTO Breakfast.
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The Language of Types
Jon Udell is talking about types and languages. Having taught undergraduate programming language concept courses and graduate level programming language theory courses, I know that just the terminology can mess a lot of people up. Here's some definitions:
- Strongly typed: the language checks the types of variables so that things "cannot go wrong" in Milner's words, at least because of type mismatches. This doesn't rule out array bounds overflows and other runtime errors, but it does keep you from assigning a pointer to a character.
- Weakly typed: in weakly typed languages, types are merely a suggestion--if the programmer wants to do something in contrast to the types, its allowed.
- Statically typed: whenever you see the word "static" in programming language discussions, it means that it happens at compile time. Statically typed languages produce type errors at compile time.
- Dynamically typed: The type checking happens at run-time.
So, here's a table with some of my favorite languages thrown in to illustrate this:
| Static | Dynamic | |
| Strong | SML, Java | Scheme |
| Weak | C | PERL, Forth |
Note that "strong" does not mean that all variables have declared types. SML is an example of a strongly typed language that uses type inference so that users can avoid declaring types. Also, keep in mind that classifications like the one above are always rife with exceptions. Even static, strong languages like Java have facilities for dynamic typing in certain cases.
I've always found typing fascinating. If you do as well, you'll enjoy the thinking of Luca Cardelli and Benjamin Pierce to name a few. You might also want to check in the Haskell programming language, which has some very innovative typing.