Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Dynamic languages are static languages

existentialtype.wordpress.com

Post reply on HN
Print view View original

11–20 of 58 posts

Re: Dynamic languages are static languages

#11

Post by regularfry »

baddox wrote: post #7

This is an impressive and informative argument. It's a shame that it's aimed at a straw man. I use the term "dynamic language" to refer to a well-recognized (though not perfectly agreed upon) set of languages. I didn't choose the term "dynamic," and I've never tried to argue that since they're dynamic , they're better/more fun/more expressive than non-dynamic languages. Hence the straw man. I use the term simply to d…

It's not so much a straw man as it is a misnomer. What he's calling a "dynamic language," I (and I think most others) would call a "dynamically typed language." It's possible to have a dynamically typed, static language - with the dynamic keyword, that's what C# is, for example.

Re: Dynamic languages are static languages

#12

Post by kgo »

ScottBurson wrote: post #5

"Since every value in a dynamic language is classified in this manner, what we are doing is agglomerating all of the values of the language into a single, gigantic (perhaps even extensible) type ." Yes, that's right, but you're overlooking the upside of doing things this way. What this gives us is the ability to define new types -- to extend the universal type, if you want to put it that way -- at runtime . No longer…

1) If CL can only sometimes enforce invariants about type sometimes, and in special cases, I'd argue that the original statement was true. You'll still be deprived in many (probably most) cases. (People have survived falls where their parachutes didn't open, but in an essay most people wouldn't say "You can of course jump out of a plane without a parachute" despite the existence proof. And saying "Although there have been cases where people have survived, you can't generally expected with any reasonable success rate to survive a fall from an airplane without a working parachute" just isn't good writing.)

2) I don't get the database analogy. When I add a column to a table, the size of the table on disk does indeed change. Not to mention the schema can be changed statically. If you add/remove/modify a Field in a FieldList, the type doesn't change. So that really isn't a static vs dynamic issue.

Re: Dynamic languages are static languages

#13

Post by Argorak »

To paraphrase an old joke about mathematicians: "He must be a computer scientist!" "How do you know?" "His answer is absolutely correct, but has no practical value."

Most of the points he makes do not touch any practical problems of this devide. For example: How do I get my XUnit tests to run if one of the functions/methods/whatever in a file does not compile because the software has changed? Ruby really excells at that: it fails at runtime. Java? Not so, it will break my whole test file at compile time. Any other number of similar examples can be found. Yes, its a problem that the language marrying both of these properties has not been found yet. But Haskell certainly isn't the one.

Also, the much respected Erik Meijer made a similar point long ago in a much better fashion: http://lambda-the-ultimate.org/node/834

Re: Dynamic languages are static languages

#15

Post by stefano »

"Now I am fully aware that “the compiler can optimize this away”, at least in some cases, but to achieve this requires one of two things (apart from unreachable levels of ingenuity that can easily, and more profitably, be expressed by the programmer in the first place). Either you give up on modular development, and rely on whole program analysis (including all libraries, shared code, the works), or you introduce a static type system precisely for the purpose of recording inter-modular dependencies."

Or you can use a tracing jit. You monitor at runtime the actual values taken by the variables and produce type-specialized code.

Re: Dynamic languages are static languages

#17

Post by tomp »

This article is full of FUD and completely misses the point of static/dynamic distinction (flame-war, if you want). It's a perfect example of someone arguing to make a point without even trying to understand the opposite position.

No one has ever argued that dynamic languages are more expressive than static languages. This is impossible, as long as we're considering Turing-complete languages. The fact that Harmony/EcmaScript 5 reference compiler was implemented on OCaml. However, it is equally futile to argue that they are less expressive[1].

"you are imposing a serious bit of runtime overhead to represent the class itself [...] and to check [...] the class [...] on the value each time it is used."

Users of dynamic languages simple trade runtime efficiency for compile-time efficiency. What's wrong with that?

The point of having multiple languages is that different languages make different things simple and easily expressible. Sure, you can do dynamic programming in Haskell or OCaml, but the language is going to work against you in some way, requiring you to specify your intension in a particularly lengthy and awkward way (think Java, except Java makes you do that for any kind of programming).

[1] Ironically, the author fails to point out the one way in which static languages are more "expressive" than dynamic languages: overloading on function's return type. I have yet to see that in a dynamically typed language.

tl;dr: All Turing-complete languages are equally expressive, but different languages make different things simple.

Re: Dynamic languages are static languages

#18

Post by tomp »

kgo wrote: post #12
ScottBurson wrote: post #5

"Since every value in a dynamic language is classified in this manner, what we are doing is agglomerating all of the values of the language into a single, gigantic (perhaps even extensible) type ." Yes, that's right, but you're overlooking the upside of doing things this way. What this gives us is the ability to define new types -- to extend the universal type, if you want to put it that way -- at runtime . No longer…

1) If CL can only sometimes enforce invariants about type sometimes, and in special cases, I'd argue that the original statement was true. You'll still be deprived in many (probably most) cases. (People have survived falls where their parachutes didn't open, but in an essay most people wouldn't say "You can of course jump out of a plane without a parachute" despite the existence proof. And saying "Although there have…

About 1): I think the point was that CL can only sometimes enforce invariants at compile time. If the compiler can't prove that something is always true or always false, it will simply emit code to do a runtime check.

Re: Dynamic languages are static languages

#19

Post by kgo »

tomp wrote: post #18
kgo wrote: post #12

Earlier quoted context omitted.

1) If CL can only sometimes enforce invariants about type sometimes, and in special cases, I'd argue that the original statement was true. You'll still be deprived in many (probably most) cases. (People have survived falls where their parachutes didn't open, but in an essay most people wouldn't say "You can of course jump out of a plane without a parachute" despite the existence proof. And saying "Although there have…

About 1): I think the point was that CL can only sometimes enforce invariants at compile time . If the compiler can't prove that something is always true or always false, it will simply emit code to do a runtime check.

But as a general principal, you can't reliably or consistently do this in a dynamic language in any sort of guaranteed fashion, which was implicit in the original statement being refuted.

Even with a runtime check, you still CAN pass in a bad value, and the program will just fail, either locally or globally.

(Not to mention that the paragraph immediately following the refuted statement starts with 'Now I am fully aware that “the compiler can optimize this away”, at least in some cases, but to achieve this requires one of two things (apart from unreachable levels of ingenuity that can easily, and more profitably, be expressed by the programmer in the first place)...')

Re: Dynamic languages are static languages

#20

Post by cscheid »

As pointed out in a comment on the original, this is a well-known source of holy wars.

The interesting bit is that this argument is one of the sides of an equivalence. Dig up the old archives of LtU,

http://lambda-the-ultimate.org/classic/lambda-archive.html

and search for the big threads. This direction of the argument (dynamic languages are static languages) was made most forcefully, in my recollection, by Frank Atanassow.

However, the other direction _also_ applies: static languages are dynamic languages. This was first pointed out in LtU, to the best of my memory, by Kevin Millikin, here:

http://lambda-the-ultimate.org/node/100#comment-1197

Someone ought to write up the old days of LtU holy wars somewhere. They taught me more about programming languages than everything I ever read anywhere else.

(edit: minor wording)

Post reply on HN