[hristov]

Well, I think that static types are much more useful than dynamic ones. Static types allow you to find errors with your program before execution and that is very important. And if you are going to go through the effort of defining types, it is much better to use static types because then you get this additional error checking. Furthermore, with static types the compiler can help in other ways, e.g. by organizing your data in memory much more efficiently.

I am not sure what you mean when you talk about the duality of static and dynamic types. One can exist without the other and most statically typed languages either forbid or strongly discourage dynamic typing.

[AnimalMuppet]

> Static types allow you to find errors with your program before execution and that is very important.

It depends on how valuable it is in your situation to be able to run a program that contains type errors.

Sometimes it's a net win. If I'm prototyping an algorithm, and can ignore the type errors so I can learn faster, that's a win. If I'm running a startup and want to just put something out there so that I can see if the market exists (or see what I should have built), it's a net win.

Sometimes it's a net loss. If I'm building an embedded system, it's likely a net loss. If I'm building something safety-critical, it's almost certainly a net loss. If I'm dealing with big money, it's almost certainly at least a big enough risk of a net loss that I can't do it.

Forget ideology. Choose the right tools for the situation.

[tome]

This is a rather glib response. Of course one should choose the right tools for the situation. Personally if I'm prototyping an algorithm I'd rather do it with types so I don't write any code that was clearly nonsense before I even tried to run it.

[AnimalMuppet]

Personally, I work the same way you do. But I've heard enough people who want the faster feedback of a REPL-like environment to accept that their approach at least feels more productive to them. It may even be more productive - for them. If so, tying them down with type specifications would slow them down, at least in the prototyping phase.

[tome]

That certainly seems like a reasonable hypothesis to explore and I'm curious to try a Haskell "EDN"-like type as defined in the article to see if that helps me prototype faster!

[dukerutledge]

I'm speaking about a philosophical dual.

For example: http://www.taoism.net/ttc/chapters/chap02.htm

[kd0amg]

One can exist without the other and most statically typed languages either forbid or strongly discourage dynamic typing.

It never seemed like that much of a prohibition to me. Dynamic types take one grand universe of "values" and divide it up in ways that (ideally) reflect differences in those values -- the number six is a different kind of thing than the string with the three letters s i x -- but what the types are is sort of arbitrary. Is an int/string pair a different type than a float/float pair? Is positive-integer a type in its own right? Is every int a rational, or just convertible into a rational? What if you have union types? After using enough dynamically typed languages, the only common factor that I'm confident holds across the whole design space is that a dynamic type is a set of values. That means static typing still leaves you free to define dynamic types that refine the classification of values imposed by your static types, and people do program with pre-/postconditions not stated in types. You just don't get the compiler's help ensuring your code is safe with regard to your own distinctions (unless maybe you build your own refinement type system on top of your language of choice).

By a similar process, dynamic typing leaves you free to define and follow your own static discipline even if a lot of programmers prefer not to. This is more or less why How to Design Programs is written/taught using a dynamic language. The static type-like discipline is a huge aspect of the curriculum, but the authors don't want to force students to commit to one specific language's typing discipline.

[didibus]

Dynamic types are definitly more useful. That's why since the last 40 years, we've almost never once had a language without it. That's why Haskell also has dynamic runtime types. Erasing them at runtime, and stopping to check their validity at runtime would be folly.

Static types are an extension, they say, do not allow types to only be defined at runtime when possible. Its not always possible, which is why static typed languages also include a runtime dynamic type system.

The debate is if the benefit of static checks on types outweighs the negative of having to spend time helping the type checker figure out the types at compile time, and limiting the use of construct that are too dynamic for the static checker to understand at compile time. That's the "dichotomy". To which someone proclaims: "Can we have a static type checker which adds no extra burden to the programmer and no limits to the type of code he wants to write?" To which OP has missed the point entirely and simply shown that you can spend more time giving the Haskell type checker info about EDN, and gain nothing since its now neither useful, nor less effort. Which was a bit dumb, but he did remark that he did it for fun and laughs, not for seriousness.