Long but great (like most of Yegge's essays, as far as I'm concerned)! This paragraph stood out for me:
"The problem is that types really are just a classification scheme to help us (and our tools) understand our semantic intent. They don't actually change the semantics; they just describe or explain the (intended) semantics. You can add type information to anything; in fact you can tag things until you're blue in the face. You can continue adding fine-grained distinctions to your code and data almost indefinitely, specializing on anything you feel like: time of day, what kind of people will be calling your APIs, anything you want."
edit: and later:
" Here's an example of what I mean by being able to tag things until you're blue in the face: Take a for-loop. It's got a type, of course: for-loop is a type of loop. It can also be viewed as a type of language construct that introduces a new scope. And it's a type that can fork program control-flow, and also a type that's introduced by a keyword and has at least two auxiliary keywords (break and continue).
You could even think of a for-loop as a type that has lots of types, as opposed to a construct like the break statement, which doesn't exhibit as much interesting and potentially type-worthy behavior. A type is just a description of something's properties and/or behavior, so you can really get carried away with overengineering your type declarations. In extreme cases, you can wind up with a separate Java interface for nearly every different method on a class. It's pretty clear why Python and Ruby are moving towards "duck typing", where you simply ask an object at runtime whether it responds to a particular message. If the object says yes, then voila — it's the right type. Case closed. "
"The problem is that types really are just a classification scheme to help us (and our tools) understand our semantic intent. They don't actually change the semantics; they just describe or explain the (intended) semantics. You can add type information to anything; in fact you can tag things until you're blue in the face. You can continue adding fine-grained distinctions to your code and data almost indefinitely, specializing on anything you feel like: time of day, what kind of people will be calling your APIs, anything you want."
edit: and later:
" Here's an example of what I mean by being able to tag things until you're blue in the face: Take a for-loop. It's got a type, of course: for-loop is a type of loop. It can also be viewed as a type of language construct that introduces a new scope. And it's a type that can fork program control-flow, and also a type that's introduced by a keyword and has at least two auxiliary keywords (break and continue).
You could even think of a for-loop as a type that has lots of types, as opposed to a construct like the break statement, which doesn't exhibit as much interesting and potentially type-worthy behavior. A type is just a description of something's properties and/or behavior, so you can really get carried away with overengineering your type declarations. In extreme cases, you can wind up with a separate Java interface for nearly every different method on a class. It's pretty clear why Python and Ruby are moving towards "duck typing", where you simply ask an object at runtime whether it responds to a particular message. If the object says yes, then voila — it's the right type. Case closed. "