3 ms·

Damien Katz: What Sucks About Erlang

52 points by nickb 19y ago

Tichy 19y ago
I also dislike =:= for equals (and I forgot the difference to ==, it wasn't clearly understandable for me from the book). =:= is hard to type, why not just use === like Javascript?
Hexstream 19y ago
There's a thought I've had in the back of my mind for quite some time but it seems so obvious that I think there must be a glaring flaw I'm not seeing otherwise it would already have been done extensively: Whenever a language has a burdensome and rigid syntax, isn't there almost necessarily a way to make a good s-expression syntax to substitute it? You'd get macros free!
- gruseom 19y ago
  If by "good s-expression syntax" you mean a representation suitable for embedding into a Lisp, then yes: it's obvious, there's no glaring flaw, you get macros for free, and it is done extensively. There's an s-expression representation (or several) for pretty much anything you'd want to integrate with a Lisp program. Examples of common ones are HTML, SQL, and Javascript. Where you don't see this done much is with general-purpose programming languages. This is probably because people who find s-expressions useful are already using Lisp as their general-purpose language. So it's mostly done for interoperability with other, pre-existing systems, like web browsers or C libraries. (You can see an example of the latter on slides 15 and 16 of http://www.xach.com/lisp/lispvan-2008-02-28.pdf http://www.xach.com/lisp/lispvan-2008-02-28.pdf.) Erlang is a fascinating intermediate case. The distinctive value of Erlang is arguably not in the language, but in its runtime and libraries (including Mnesia). For this reason, the "general-purpose" caveat doesn't apply, and it's easy to see why someone might want to build a Lisp program on top of the Erlang runtime via embedded s-expressions. I seem to recall that there was a game company already doing this. If anyone knows about that or other examples, please post them here.
  - lg 19y ago
    robert virding (of "hello, robert" erlang movie fame) released "lisp-flavoured erlang" recently. Haven't played with it yet... http://groups.google.com/group/erlang-questions/browse_thread/thread/adfe375287d4bef4/4a9127e701f5e2db http://groups.google.com/group/erlang-questions/browse_threa...
    - eru 19y ago
      Hello, Dave.
- yters 19y ago
  Aren't all languages sexps at the parse tree level? Lisp is basically a language without the syntactic top layer.
  - deleted 19y ago
    [deleted]
  - obdurak 19y ago
    You could go further and say that all languages are lists of characters and wish for a language without the lexical top layer.
a-priori 19y ago
Most of those are minor nit-picks, but I do agree with him about string handling. Strings should be tagged. "dog" should be equal to {string, [100, 111, 103]} or something.
jey 19y ago
Why write this: f(X) -> X1 = foo(X), X2 = fab(X1), X3 = bar(X2), baz(X3). When you can write this? (I assume this is legal) f(X) -> baz(bar(fab(foo(X)))).
- eru 19y ago
  Sometimes shorter lines are easier to read. But in most of the cases you should be right. You can even be more consice by using point-free form: f = baz . bar . fab . foo [Haskell syntax - sorry, I do not know enough about Erlang - but something like this should be possible.]
- mechanical_fish 19y ago
  I think this is just toy-example syndrome. In my experience the real-world example looks more like this: f(X) -> X1 = foo(X, "Blah blah blah", true, :definitely, :ack), X2 = fab(X1, X, sizeof(X), X-1, bar(X, "martini"), :with_bells_on, :pdq), X3 = bar(X2, "fim tim lim bim whim bim bus stop"), baz(X3). Try chaining that and see how readable it is.
  - jey 19y ago
    Touché.
davidw 19y ago
You basically shouldn't be using 'if' in Erlang - it's very rare that a pattern match wouldn't be a better option. That said, I agree with him: http://journal.dedasys.com/articles/2007/09/22/erlang http://journal.dedasys.com/articles/2007/09/22/erlang

52 points by nickb 19y ago

Tichy 19y ago

I also dislike =:= for equals (and I forgot the difference to ==, it wasn't clearly understandable for me from the book). =:= is hard to type, why not just use === like Javascript?

Hexstream 19y ago

There's a thought I've had in the back of my mind for quite some time but it seems so obvious that I think there must be a glaring flaw I'm not seeing otherwise it would already have been done extensively: Whenever a language has a burdensome and rigid syntax, isn't there almost necessarily a way to make a good s-expression syntax to substitute it? You'd get macros free!

gruseom 19y ago
If by "good s-expression syntax" you mean a representation suitable for embedding into a Lisp, then yes: it's obvious, there's no glaring flaw, you get macros for free, and it is done extensively. There's an s-expression representation (or several) for pretty much anything you'd want to integrate with a Lisp program. Examples of common ones are HTML, SQL, and Javascript. Where you don't see this done much is with general-purpose programming languages. This is probably because people who find s-expressions useful are already using Lisp as their general-purpose language. So it's mostly done for interoperability with other, pre-existing systems, like web browsers or C libraries. (You can see an example of the latter on slides 15 and 16 of http://www.xach.com/lisp/lispvan-2008-02-28.pdf http://www.xach.com/lisp/lispvan-2008-02-28.pdf.) Erlang is a fascinating intermediate case. The distinctive value of Erlang is arguably not in the language, but in its runtime and libraries (including Mnesia). For this reason, the "general-purpose" caveat doesn't apply, and it's easy to see why someone might want to build a Lisp program on top of the Erlang runtime via embedded s-expressions. I seem to recall that there was a game company already doing this. If anyone knows about that or other examples, please post them here.
- lg 19y ago
  robert virding (of "hello, robert" erlang movie fame) released "lisp-flavoured erlang" recently. Haven't played with it yet... http://groups.google.com/group/erlang-questions/browse_thread/thread/adfe375287d4bef4/4a9127e701f5e2db http://groups.google.com/group/erlang-questions/browse_threa...
  - eru 19y ago
    Hello, Dave.
yters 19y ago
Aren't all languages sexps at the parse tree level? Lisp is basically a language without the syntactic top layer.
- deleted 19y ago
  [deleted]
- obdurak 19y ago
  You could go further and say that all languages are lists of characters and wish for a language without the lexical top layer.

a-priori 19y ago

Most of those are minor nit-picks, but I do agree with him about string handling. Strings should be tagged. "dog" should be equal to {string, [100, 111, 103]} or something.

jey 19y ago

Why write this: f(X) -> X1 = foo(X), X2 = fab(X1), X3 = bar(X2), baz(X3). When you can write this? (I assume this is legal) f(X) -> baz(bar(fab(foo(X)))).

eru 19y ago
Sometimes shorter lines are easier to read. But in most of the cases you should be right. You can even be more consice by using point-free form: f = baz . bar . fab . foo [Haskell syntax - sorry, I do not know enough about Erlang - but something like this should be possible.]
mechanical_fish 19y ago
I think this is just toy-example syndrome. In my experience the real-world example looks more like this: f(X) -> X1 = foo(X, "Blah blah blah", true, :definitely, :ack), X2 = fab(X1, X, sizeof(X), X-1, bar(X, "martini"), :with_bells_on, :pdq), X3 = bar(X2, "fim tim lim bim whim bim bus stop"), baz(X3). Try chaining that and see how readable it is.
- jey 19y ago
  Touché.

davidw 19y ago

You basically shouldn't be using 'if' in Erlang - it's very rare that a pattern match wouldn't be a better option. That said, I agree with him: http://journal.dedasys.com/articles/2007/09/22/erlang http://journal.dedasys.com/articles/2007/09/22/erlang