5 ms·

Macros would solve this problem nicely if they we're available. I sure wish first class macros were on the golang roadmap.

tptacek 8y ago
If you want to code in a language with macros, pick a language with macros. They tend not to look like Go (or C, or C++), because part of what makes macros effective is that coding in those languages is pretty close to working with their ASTs. Writing a Lisp-like macro for Go sounds like it would actually be more annoying than simply writing a codegen for it.
- bpicolo 8y ago
  I don't think there's anything precluding Go from making it possible, other than the maintainers' desire to not have macros. Rust gives you the power here, and as a result has some tremendous serialization libs: https://github.com/serde-rs/serde https://github.com/serde-rs/serde Macros don't need to be as simple to use as in lisps to be useful - the rare library like serialization that can really benefit from them can be worth the language feature
  - tptacek 8y ago
    Rust is a good counterexample, yep.
- phamilton 8y ago
  The end result with macros is far more seamless than with codegen, the point being that a consumer of the library doesn't even need to know about the macros. The code just works like the reflection approach, but without the runtime penalty. Codegen on the other hand makes an implementation detail a maintenance cost for the user of the library.
  - stcredzero 8y ago
    The end result with macros is far more seamless than with codegen, the point being that a consumer of the library doesn't even need to know about the macros. A double edged sword, that! Sometimes the end result with things like macros, is that it so seamless, that there is precious little to figure out what went wrong. Often, if your nifty new facility seems magic, its bugs are going to seem doubly magic. Not too long ago, I had to debug an exception for which no source code existed. It only existed as the confluence of 3 C++ templates. Codegen on the other hand makes an implementation detail a maintenance cost for the user of the library. I've heard veteran programmers say that there should be a separation of labor when it comes to libraries. Only certain people make good library writers, in the same way that only certain people make excellent musical accompanists. To be an excellent accompanist, the accompanist should have some sense of what it's like to be the lead. (So should themselves be able to take the lead.) The accompanist should have the perspective to not let his ego get in the way. The accompanist should be giving the lead what she wants, but modulated through their own expertise and sense of taste. (As opposed to mindlessly always giving everything asked for.) If there is a separation of responsibility, why would codegen be such a burden? If the library has to change so often, perhaps the responsibilities aren't distributed optimally?
    - pcwalton 8y ago
      Macros usually make debugging easier than code generators do. That's because quasiquote and similar operators let you debug code, not code that generates code. I'm the first to admit that macros have downsides compared to not having them in the language, but ease of debugging generated code isn't one of those downsides.
      - stcredzero 8y ago
        I've generally found that C/C++ macros make debugging harder. Debuggers don't always deal with debugging them the most straightforward thing. That's because quasiquote and similar operators let you debug code, not code that generates code. What I've found is that you can debug the generated code to debug the code generator. Code generators shouldn't be used to do something terribly complicated. I'd agree with you that code generators doing complicated things is a code smell. Leave those to native syntax, provided it's not as badly thought out as templates.
- pcwalton 8y ago
  S-expressions aren't actually necessary for macros to work. You just have to be able to separate "READ" from "EXPAND" (to use Lisp-ish terminology). I believe, but am not sure, that this is possible for Go. (Of course, whether this is a good idea is another thing entirely. I probably wouldn't have included macros if I had been put in charge of Go 1.0, given Go's goals of simplicity.) More on this from my former colleague Dave Herman, who did his dissertation on macros: http://calculist.org/blog/2012/04/17/homoiconicity-isnt-the-point/ http://calculist.org/blog/2012/04/17/homoiconicity-isnt-the-...
- vorg 8y ago
  An alternative to both Lisp-like macros and code generation is to trigger macros via annotations in the syntax, and for the macro to manipulate the AST directly using the "go/ast" package. Apache Groovy, which has the same curly-braces style syntax as Golang, does it like this.

tptacek 8y ago

If you want to code in a language with macros, pick a language with macros. They tend not to look like Go (or C, or C++), because part of what makes macros effective is that coding in those languages is pretty close to working with their ASTs. Writing a Lisp-like macro for Go sounds like it would actually be more annoying than simply writing a codegen for it.

bpicolo 8y ago
I don't think there's anything precluding Go from making it possible, other than the maintainers' desire to not have macros. Rust gives you the power here, and as a result has some tremendous serialization libs: https://github.com/serde-rs/serde https://github.com/serde-rs/serde Macros don't need to be as simple to use as in lisps to be useful - the rare library like serialization that can really benefit from them can be worth the language feature
- tptacek 8y ago
  Rust is a good counterexample, yep.
phamilton 8y ago
The end result with macros is far more seamless than with codegen, the point being that a consumer of the library doesn't even need to know about the macros. The code just works like the reflection approach, but without the runtime penalty. Codegen on the other hand makes an implementation detail a maintenance cost for the user of the library.
- stcredzero 8y ago
  The end result with macros is far more seamless than with codegen, the point being that a consumer of the library doesn't even need to know about the macros. A double edged sword, that! Sometimes the end result with things like macros, is that it so seamless, that there is precious little to figure out what went wrong. Often, if your nifty new facility seems magic, its bugs are going to seem doubly magic. Not too long ago, I had to debug an exception for which no source code existed. It only existed as the confluence of 3 C++ templates. Codegen on the other hand makes an implementation detail a maintenance cost for the user of the library. I've heard veteran programmers say that there should be a separation of labor when it comes to libraries. Only certain people make good library writers, in the same way that only certain people make excellent musical accompanists. To be an excellent accompanist, the accompanist should have some sense of what it's like to be the lead. (So should themselves be able to take the lead.) The accompanist should have the perspective to not let his ego get in the way. The accompanist should be giving the lead what she wants, but modulated through their own expertise and sense of taste. (As opposed to mindlessly always giving everything asked for.) If there is a separation of responsibility, why would codegen be such a burden? If the library has to change so often, perhaps the responsibilities aren't distributed optimally?
  - pcwalton 8y ago
    Macros usually make debugging easier than code generators do. That's because quasiquote and similar operators let you debug code, not code that generates code. I'm the first to admit that macros have downsides compared to not having them in the language, but ease of debugging generated code isn't one of those downsides.
    - stcredzero 8y ago
      I've generally found that C/C++ macros make debugging harder. Debuggers don't always deal with debugging them the most straightforward thing. That's because quasiquote and similar operators let you debug code, not code that generates code. What I've found is that you can debug the generated code to debug the code generator. Code generators shouldn't be used to do something terribly complicated. I'd agree with you that code generators doing complicated things is a code smell. Leave those to native syntax, provided it's not as badly thought out as templates.
pcwalton 8y ago
S-expressions aren't actually necessary for macros to work. You just have to be able to separate "READ" from "EXPAND" (to use Lisp-ish terminology). I believe, but am not sure, that this is possible for Go. (Of course, whether this is a good idea is another thing entirely. I probably wouldn't have included macros if I had been put in charge of Go 1.0, given Go's goals of simplicity.) More on this from my former colleague Dave Herman, who did his dissertation on macros: http://calculist.org/blog/2012/04/17/homoiconicity-isnt-the-point/ http://calculist.org/blog/2012/04/17/homoiconicity-isnt-the-...
vorg 8y ago
An alternative to both Lisp-like macros and code generation is to trigger macros via annotations in the syntax, and for the macro to manipulate the AST directly using the "go/ast" package. Apache Groovy, which has the same curly-braces style syntax as Golang, does it like this.