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I think there's one other important lisp feature that hasn't been widely adopted: compile-time metaprogramming. A lot of lisp macro use boils down "allow develo

I think there's one other important lisp feature that hasn't been widely adopted: compile-time metaprogramming. A lot of lisp macro use boils down "allow developer to generate lots of new code based on tiny fragments of code he writes." The Python community has adopted this to good effect, but the Java/C++ community really hasn't. The funny thing is, the need for good code generation doesn't go away simply because the language provides no facilities for it. That's why C++'s broken template system is so often abused to provide compile-time metaprogramming. And that's why Java added annotation factory support. The preferred use for annotation factories is to register a factory class that the compiler will call when compiling code that uses your annotation. Your factory can then access a special compile time API that allows it to create new Java source files based on the AST that the compiler feeds it. More sketchily, your factory can modify the AST in place. This is an insanely baroque way of getting compile time metaprogramming but it solves a real problem.

nostrademons 16y ago
I dunno what life inside other big companies is like, but Google uses compile-time metaprogramming all the time. There're tons (perhaps too many) "little languages" used inside Google. Some have even been open-sourced, eg. protobufs, google-ctemplates, Closure Compiler. And if their open-source output is any guide, FaceBook uses tons of little languages as well. It's just that they're done the UNIX way, with a small miniature compiler or XML substrate, instead of the Lisp way, where you write everything in S-exprs. This tends to make the little languages easier to grok for users but harder to implement, which tends to be a good tradeoff, as there will be far more users than implementers of a programming language.
- MichaelSalib 16y ago
  Sure, you can totally do compile-time metaprogramming without language support, but the barrier to entry is much higher. That means that, at the margin, you're less likely to try it, especially for small projects. And most projects start small. I totally agree that good development shops do lots of compile-time metaprogramming. The issue is whether they do enough when dealing with problems (that start out as) too small to justify writing a full blown parser/compiler, and if they don't, how much of the shortage is attributable to a lack of language support in C++/Java.

nostrademons 16y ago

I dunno what life inside other big companies is like, but Google uses compile-time metaprogramming all the time. There're tons (perhaps too many) "little languages" used inside Google. Some have even been open-sourced, eg. protobufs, google-ctemplates, Closure Compiler. And if their open-source output is any guide, FaceBook uses tons of little languages as well. It's just that they're done the UNIX way, with a small miniature compiler or XML substrate, instead of the Lisp way, where you write everything in S-exprs. This tends to make the little languages easier to grok for users but harder to implement, which tends to be a good tradeoff, as there will be far more users than implementers of a programming language.

MichaelSalib 16y ago
Sure, you can totally do compile-time metaprogramming without language support, but the barrier to entry is much higher. That means that, at the margin, you're less likely to try it, especially for small projects. And most projects start small. I totally agree that good development shops do lots of compile-time metaprogramming. The issue is whether they do enough when dealing with problems (that start out as) too small to justify writing a full blown parser/compiler, and if they don't, how much of the shortage is attributable to a lack of language support in C++/Java.