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The evidence for this statement best comes from a research paper* that attempts to formalize language expressibility . According to their formalization, languag

by sreque 15y ago

The evidence for this statement best comes from a research paper* that attempts to formalize language expressibility . According to their formalization, language features are classified as macro expressible if they can be implemented in terms of local syntax transformations of other language features. The paper shows that expressivity, power, and conciseness come the most from those features that are not macro expressible. Yet, none of Xtends features seem to be in that category. Since most languages don't have macros or compiler plugin frameworks, there can still be great value in adding macro expressible features, but, as I said in my previous post, these are less likely to be game changers in terms of productivity. These are the kinds of features that IDEs can make up for with templates and code generators. As an example, an anonymous class might be bulky, but it essentially provides the same feature set as a closure and the IDE is good at writing most of the boilerplate for you. *see www.ccs.neu.edu/scheme/pubs/scp91-felleisen.ps.gz

buff-a 15y ago
local syntax transformations This is the key concept, and I disagree with you that this is all Xtend is. Its why I think you are wrong. Specifically, the Xtend transformation is adding information to the java code it generates that it must infer from the Xtend source code. It is precisely not a local syntax transformation. I think you are assuming that because they make it look easy, that all it is is another macro language with, as you say, local syntax transformations.
- bdj 15y ago
  You misunderstand what a local syntax transformation is. A syntax transformation is just a function that takes syntax as input and returns syntax as output. The function can be arbitrarily complex, even "inferring" things from the input syntax. The key point is whether the transform is local or global. An example of a global transform is turning a program into continuation-passing style because it must change every function definition and function call in the program. The transforms that Xtend is doing appear to be local. Converting closures to anonymous inner classes is a local transformation. Their "type inference" isn't real whole-program type inference, it just saves keystrokes within certain expressions. The fact that they can show you the underlying Java code that each new feature turns into indicates that the transforms are local. Also, these types of transformations really are trivial in languages with full-featured macro systems (like most LISP dialects).
  - buff-a 15y ago
    The referenced paper is way over my head, so I'll just say where I'm having difficulty and perhaps you can help me out. Java doesn't have closures. Xtend does. Closures seem to me to satisfy the paper's definition of providing greater expressibility. Certainly, I've done a lot of C# and Java, and having closures in C# has greatly influenced how I write code. And yet closures appear to be what you claim is a local syntax transform, and therefor can not add any expressibility to the language. I am confused. Update: I didnt downvote you btw.
    - skrebbel 15y ago
      Java's anonymous inner classes basically work like closures, except that they require that you mark some variables as final and that you have to write a lot of boilerplate. My underbelly feeling is that xtend's closures merely compile to those. Often, such closures are enough. E.g. with Google Guava's predicates and filter/map methods, you can do with Java (guava + anonymous inner classes) what LINQ enables in C# (System.Linq + lambda expressions). The Java version has a lot more line noise than the C# version, however, which is what Xtend fixes. I love it.
      - buff-a 15y ago
        And C++ classes merely compile to C methods with mangled names that also take a pointer to a C struct, the first member of which is a pointer to an array of such functions, and whose remaining members are the fields. If you (or GP) are going to argue that C++ is no more productive than C simply because cfront turns C++ into C, then I think theory has gotten in the way of reality.
        skrebbel 15y ago
        Eh. I was arguing the direct opposite. I have the feeling that you're just looking to pick a fight.
        scott_s 15y ago
        I think the key difference is if the language feature automates a kind of abstraction that was manual in the other language. For example, one can write object-oriented programs in C, but you have to do it all yourself. And C++ programs can, as you pointed out, be translated to equivalent C programs. But classes and objects in C++ are language level abstractions that don't exist in C. In that regard, I agree with you: if you want to do OO programming, one can be more productive in C++ than C. I have read much detail about Extend, but to me, the key question becomes: does it have language level abstractions that Java does not? I think closures and anonymous functions qualify, but I don't know if they're enough to make that much of a difference. But what I've seen of Extend, with the exception of closures and anonymous functions, it doesn't actually have any new abstractions. It just cleans up the syntax.
Someone 15y ago
"The paper shows that expressivity, power, and conciseness come the most from those features…" I do not accept your implicit claim that a language must be more expressive, powerful, or concise to be more productive. As a counter-argument for the expressive claim, consider a language that required one to prefix each line with the number of non-blank characters it contains. I am fairly sure I would be more productive using a preprocessor that computed those prefixes for me. Real world examples of the same are the abolishment of line numbers in Basic, assemblers that know about structure offsets, the C preprocessor, and type inference. Each, I think, helped increase productivity. 'Power' cannot be a factor at all, as basicly all programming language are equally powerful; there are no degrees of Turing completeness. That leaves conciseness. I do not think that claim would need debunking, but for completeness: if that helped productivity, everybody would use single-character variable and function names (should mostly be possible in languages that allow Unicode source code), and program in APL or perl.
- ekabanov 15y ago
  There are no real Turing-complete languages, as Turing-completeness requires infinite hardware. And certainly there are degrees of incompleteness, expressed by which programs run out of memory faster.
bermanoid 15y ago
First, the fact that this language is coming from the Eclipse team suggests to me that they are probably not limited to macro transformations, at least at a fundamental level. The main reason Java folks like Eclipse is that it has a global understanding of Java code (this is why plugins for text editors tend to flat out suck compared to real Java IDEs, they are mostly dealing with local information), and I'd imagine that people working on an IDE that made non-local code comprehension a core focus of the product would make sure they're able to extract that information fairly easily from a language that they designed themselves. That aside (since I agree that most of what they're doing appears to be fairly local, at the moment), what are the features that you miss in Java anyways, as compared to something like Ruby or Python, once you add closures and a bit of syntax sugar to cut out boilerplate? Past that, I can't think of much that people actually use day-to-day (and no, callcc doesn't count) in Ruby or Python that's not already possible in Java, albeit with a little more line noise. Can you? When I look at code across many languages, the thing that makes Java code stand out as particularly clumsy is that it forces a lot of local verbosity, and that functional programming is very clumsy due to the lack of closures (though it's possible if you're willing to swallow your pride and endure some pain).
- celer 15y ago
  The single thing I would say Java is missing, from the perspective of a beginner, is the ability to change code while running it. Eval and Exec are useful functions, and there is no way to replicate them in Java. Lists in Java are an unholy pain that redefine cruelty in an entirely new way. You can't make a list, to the best of my knowledge, that accepts arbitrary inputs. Does the utter lack of a slice operator count for the addition of multiple lines of code to replace what is normally three or four characters? Please, tell me how. This is an honest question. I have been learning Java since school started, and I miss my functional techniques.

by sreque 15y ago

buff-a 15y ago

local syntax transformations This is the key concept, and I disagree with you that this is all Xtend is. Its why I think you are wrong. Specifically, the Xtend transformation is adding information to the java code it generates that it must infer from the Xtend source code. It is precisely not a local syntax transformation. I think you are assuming that because they make it look easy, that all it is is another macro language with, as you say, local syntax transformations.

bdj 15y ago
You misunderstand what a local syntax transformation is. A syntax transformation is just a function that takes syntax as input and returns syntax as output. The function can be arbitrarily complex, even "inferring" things from the input syntax. The key point is whether the transform is local or global. An example of a global transform is turning a program into continuation-passing style because it must change every function definition and function call in the program. The transforms that Xtend is doing appear to be local. Converting closures to anonymous inner classes is a local transformation. Their "type inference" isn't real whole-program type inference, it just saves keystrokes within certain expressions. The fact that they can show you the underlying Java code that each new feature turns into indicates that the transforms are local. Also, these types of transformations really are trivial in languages with full-featured macro systems (like most LISP dialects).
- buff-a 15y ago
  The referenced paper is way over my head, so I'll just say where I'm having difficulty and perhaps you can help me out. Java doesn't have closures. Xtend does. Closures seem to me to satisfy the paper's definition of providing greater expressibility. Certainly, I've done a lot of C# and Java, and having closures in C# has greatly influenced how I write code. And yet closures appear to be what you claim is a local syntax transform, and therefor can not add any expressibility to the language. I am confused. Update: I didnt downvote you btw.
  - skrebbel 15y ago
    Java's anonymous inner classes basically work like closures, except that they require that you mark some variables as final and that you have to write a lot of boilerplate. My underbelly feeling is that xtend's closures merely compile to those. Often, such closures are enough. E.g. with Google Guava's predicates and filter/map methods, you can do with Java (guava + anonymous inner classes) what LINQ enables in C# (System.Linq + lambda expressions). The Java version has a lot more line noise than the C# version, however, which is what Xtend fixes. I love it.
    - buff-a 15y ago
      And C++ classes merely compile to C methods with mangled names that also take a pointer to a C struct, the first member of which is a pointer to an array of such functions, and whose remaining members are the fields. If you (or GP) are going to argue that C++ is no more productive than C simply because cfront turns C++ into C, then I think theory has gotten in the way of reality.
      - skrebbel 15y ago
        Eh. I was arguing the direct opposite. I have the feeling that you're just looking to pick a fight.
      - scott_s 15y ago
        I think the key difference is if the language feature automates a kind of abstraction that was manual in the other language. For example, one can write object-oriented programs in C, but you have to do it all yourself. And C++ programs can, as you pointed out, be translated to equivalent C programs. But classes and objects in C++ are language level abstractions that don't exist in C. In that regard, I agree with you: if you want to do OO programming, one can be more productive in C++ than C. I have read much detail about Extend, but to me, the key question becomes: does it have language level abstractions that Java does not? I think closures and anonymous functions qualify, but I don't know if they're enough to make that much of a difference. But what I've seen of Extend, with the exception of closures and anonymous functions, it doesn't actually have any new abstractions. It just cleans up the syntax.

Someone 15y ago

"The paper shows that expressivity, power, and conciseness come the most from those features…" I do not accept your implicit claim that a language must be more expressive, powerful, or concise to be more productive. As a counter-argument for the expressive claim, consider a language that required one to prefix each line with the number of non-blank characters it contains. I am fairly sure I would be more productive using a preprocessor that computed those prefixes for me. Real world examples of the same are the abolishment of line numbers in Basic, assemblers that know about structure offsets, the C preprocessor, and type inference. Each, I think, helped increase productivity. 'Power' cannot be a factor at all, as basicly all programming language are equally powerful; there are no degrees of Turing completeness. That leaves conciseness. I do not think that claim would need debunking, but for completeness: if that helped productivity, everybody would use single-character variable and function names (should mostly be possible in languages that allow Unicode source code), and program in APL or perl.

ekabanov 15y ago
There are no real Turing-complete languages, as Turing-completeness requires infinite hardware. And certainly there are degrees of incompleteness, expressed by which programs run out of memory faster.

bermanoid 15y ago

First, the fact that this language is coming from the Eclipse team suggests to me that they are probably not limited to macro transformations, at least at a fundamental level. The main reason Java folks like Eclipse is that it has a global understanding of Java code (this is why plugins for text editors tend to flat out suck compared to real Java IDEs, they are mostly dealing with local information), and I'd imagine that people working on an IDE that made non-local code comprehension a core focus of the product would make sure they're able to extract that information fairly easily from a language that they designed themselves. That aside (since I agree that most of what they're doing appears to be fairly local, at the moment), what are the features that you miss in Java anyways, as compared to something like Ruby or Python, once you add closures and a bit of syntax sugar to cut out boilerplate? Past that, I can't think of much that people actually use day-to-day (and no, callcc doesn't count) in Ruby or Python that's not already possible in Java, albeit with a little more line noise. Can you? When I look at code across many languages, the thing that makes Java code stand out as particularly clumsy is that it forces a lot of local verbosity, and that functional programming is very clumsy due to the lack of closures (though it's possible if you're willing to swallow your pride and endure some pain).

celer 15y ago
The single thing I would say Java is missing, from the perspective of a beginner, is the ability to change code while running it. Eval and Exec are useful functions, and there is no way to replicate them in Java. Lists in Java are an unholy pain that redefine cruelty in an entirely new way. You can't make a list, to the best of my knowledge, that accepts arbitrary inputs. Does the utter lack of a slice operator count for the addition of multiple lines of code to replace what is normally three or four characters? Please, tell me how. This is an honest question. I have been learning Java since school started, and I miss my functional techniques.