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> You should check out Racket's macro system. It's a lot more sophisticated than Common Lisp's. Common Lisp macros are to C (e.g., gensym is a macro-level mallo

> You should check out Racket's macro system. It's a lot more sophisticated than Common Lisp's. Common Lisp macros are to C (e.g., gensym is a macro-level malloc, you need to manually destructure S-expressions, etc.) as Racket macros are to ML and Haskell (syntax objects are aware of which variables are in scope, so automatic fresh name generation is possible; user-defined syntax classes and patterns let you process arbitrarily complicated structures in a sane way, etc.). Agreed. I did play around with this part of Racket quite a bit and I'm convinced that it's the best system if I wanted to create a domain-specific language. But it still runs into the problem where you're defining a new language with new syntax, which forces you to define even more new language with more syntax in order to make that language useful. It's the best way to build a DSL But given we already have a pretty good multi-purpose language with a lot of work put into it (Racket) the number of situations where it's worthwhile to create an equally-well-thought-out DSL is pretty low. Racket makes it easier, but it's still not easy. Add to this the fact that other people are going to write half-assed DSLs in my code, the net tradeoff is still usually negative, even with Rackets clearly superior macro system. > Furthermore, “code as data” itself is only true with a caveat: the full version is ”code in an object language is data in the metalanguage”, which is obvious to anyone who has written a compiler. Uh, I've written a compiler and that's not obvious. If you want to disagree with me on what "code as data" means, you're welcome to do so. As long as you understood what I said I don't care which words got me there. > Common Lisp is a ridiculously powerful language, but it isn't a functional language. It fails to meet the zeroth nonnegotiable requirement in a practical functional language, namely, a notion of compound value: https://news.ycombinator.com/item?id=12199981 https://news.ycombinator.com/item?id=12199981 How about we assume when I said "functional programming" I'm using the Wikipedia definition[1]. [1] https://en.wikipedia.org/wiki/Functional_programming https://en.wikipedia.org/wiki/Functional_programming

catnaroek 10y ago
> Racket makes it easier, but it's still not easy. Add to this the fact that other people are going to write half-assed DSLs in my code, the net tradeoff is still usually negative, even with Rackets clearly superior macro system. You have a point there. In any case, metaprogramming shouldn't be an everyday activity. > If you want to disagree with me on what "code as data" means, you're welcome to do so. What I mean by “code in an object language is data in the metalanguage” is that, in the (meta)language in which you're writing a compiler or interpreter, the (object language) program that you're processing is represented as a data structure (say, as a syntax tree). It's just a triviality, I'm not saying anything really deep. From this point of view, it should be clear that a macro system is essentially a language-integrated facility for writing compiler plugins. > How about we assume when I said "functional programming" I'm using the Wikipedia definition[1]. My definition of functional programming is “using (procedures that compute) mathematical functions whenever possible”. A mathematical function is a mapping from values to values, so if a language doesn't have a good notion of (possibly compound) value, then you're going to run into trouble writing procedures that compute mathematical functions. EDIT: The Wikipedia definition essentially agrees with me. “In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions [emphasis mine] and avoids changing-state and mutable data.” And a mathematical function is a mapping from values (in a domain) to values (in a codomain). Again, quoting Wikipedia[0]: “A function can be defined by any mathematical condition relating each argument (input value) to the corresponding output value.” [0] https://en.wikipedia.org/wiki/Function_(mathematics)#Specifying_a_function https://en.wikipedia.org/wiki/Function_(mathematics)#Specify...
- unpop-opinion 10y ago
  > What I mean by “code in an object language is data in the metalanguage” is that, in the metalanguage in which you're writing a compiler or interpreter, the object language program that you're processing is represented as a data structure (say, as a syntax tree). It's just a triviality, I'm not saying anything really deep. I understood what you were saying, and didn't ask for an explanation. I just don't see why you felt the need to correct me on my calling first=class functions "code as data" and substitute your own definition that had nothing to do with what I was saying. > My definition of functional programming is “using (procedures that compute) mathematical functions whenever possible”. A mathematical function is a mapping from values to values, so if a language doesn't have a good notion of (possibly compound) value, then you're going to run into trouble writing procedures that compute mathematical functions. Again, I didn't ask what your definition was, because it wasn't relevant to the conversation. You're basically interrupting me to tell me I'm not using the same definitions of words as you are, and it's not particularly endearing. If you don't understand what I'm saying, I'll be happy to explain. If you do, however, understand what I'm saying well enough to correct me on my usage of the English language, then my usage of the language has been clear enough for my goals, so I wouldn't be interested in your corrections even if they represented HN's common usage (which they don't).
  - catnaroek 10y ago
    > I just don't see why you felt the need to correct me on my calling first=class functions "code as data" Because first-class functions aren't “code as data”. When you have a first-class function, the only thing you can do with it is call it. If it were a data structure, you could analyze its constituent parts. > You're basically interrupting me to tell me I'm not using the same definitions of words as you are, The Wikipedia article you linked says: “In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions [emphasis mine] and avoids changing-state and mutable data.” The emphasized part is just what I said. That a mathematical function is a mapping from values to values is unquestionable - it's not something I'm saying, it's a mathematical fact. So if you can't express compound values, you're limited to a world where mathematical functions can only manipulate primitive values.

catnaroek 10y ago

> Racket makes it easier, but it's still not easy. Add to this the fact that other people are going to write half-assed DSLs in my code, the net tradeoff is still usually negative, even with Rackets clearly superior macro system. You have a point there. In any case, metaprogramming shouldn't be an everyday activity. > If you want to disagree with me on what "code as data" means, you're welcome to do so. What I mean by “code in an object language is data in the metalanguage” is that, in the (meta)language in which you're writing a compiler or interpreter, the (object language) program that you're processing is represented as a data structure (say, as a syntax tree). It's just a triviality, I'm not saying anything really deep. From this point of view, it should be clear that a macro system is essentially a language-integrated facility for writing compiler plugins. > How about we assume when I said "functional programming" I'm using the Wikipedia definition[1]. My definition of functional programming is “using (procedures that compute) mathematical functions whenever possible”. A mathematical function is a mapping from values to values, so if a language doesn't have a good notion of (possibly compound) value, then you're going to run into trouble writing procedures that compute mathematical functions. EDIT: The Wikipedia definition essentially agrees with me. “In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions [emphasis mine] and avoids changing-state and mutable data.” And a mathematical function is a mapping from values (in a domain) to values (in a codomain). Again, quoting Wikipedia[0]: “A function can be defined by any mathematical condition relating each argument (input value) to the corresponding output value.” [0] https://en.wikipedia.org/wiki/Function_(mathematics)#Specifying_a_function https://en.wikipedia.org/wiki/Function_(mathematics)#Specify...

unpop-opinion 10y ago
> What I mean by “code in an object language is data in the metalanguage” is that, in the metalanguage in which you're writing a compiler or interpreter, the object language program that you're processing is represented as a data structure (say, as a syntax tree). It's just a triviality, I'm not saying anything really deep. I understood what you were saying, and didn't ask for an explanation. I just don't see why you felt the need to correct me on my calling first=class functions "code as data" and substitute your own definition that had nothing to do with what I was saying. > My definition of functional programming is “using (procedures that compute) mathematical functions whenever possible”. A mathematical function is a mapping from values to values, so if a language doesn't have a good notion of (possibly compound) value, then you're going to run into trouble writing procedures that compute mathematical functions. Again, I didn't ask what your definition was, because it wasn't relevant to the conversation. You're basically interrupting me to tell me I'm not using the same definitions of words as you are, and it's not particularly endearing. If you don't understand what I'm saying, I'll be happy to explain. If you do, however, understand what I'm saying well enough to correct me on my usage of the English language, then my usage of the language has been clear enough for my goals, so I wouldn't be interested in your corrections even if they represented HN's common usage (which they don't).
- catnaroek 10y ago
  > I just don't see why you felt the need to correct me on my calling first=class functions "code as data" Because first-class functions aren't “code as data”. When you have a first-class function, the only thing you can do with it is call it. If it were a data structure, you could analyze its constituent parts. > You're basically interrupting me to tell me I'm not using the same definitions of words as you are, The Wikipedia article you linked says: “In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions [emphasis mine] and avoids changing-state and mutable data.” The emphasized part is just what I said. That a mathematical function is a mapping from values to values is unquestionable - it's not something I'm saying, it's a mathematical fact. So if you can't express compound values, you're limited to a world where mathematical functions can only manipulate primitive values.