Hacker News Reader

Comment by voyou | Hacker News Reader

That's true, but that any "dynamically-typed and lexically scoped languages" with closures and first-class functions could be considered mainstream is fairly new. Crockford wrote "JavaScript: The World's Most Misunderstood Programming Language", which I think is the source of the idea that JavaScript is like Scheme, back in 2001. At that point, Ruby was almost unknown, Python was fairly minor, PHP didn't have closures or first-class functions; the other major programming languages were statically-typed things like C++ and Java.

So I think it's worth remembering that it's really a very recent development that we can now treat it as obvious that a language like JavaScript would contain the things it has in common with Scheme.

View on HN

> That's true, but that any "dynamically-typed and lexically scoped languages" with closures and first-class functions could be considered mainstream is fairly new.

When I first started thinking about writing this post, I was considering going from the angle of "JS was Scheme when Crockford said that but now every language has caught up and we're all Scheme now" but somehow a different post fell out of my head when I started writing.

Perl was big in 2001 and had closures and first-class functions.

And let's not forget great book Higher-Order Perl: Transforming Programs with Programs http://hop.perl.plover.com/

Well, Perl is on a level not many languages dare touch. If I'm not mistaken, you can execute arbitrary code during compilation and generate arbitrary source. Which in turn might be executed to generate more stuff...

So, just like Lisp, then.

You can do that with any language that has an eval function. Eval takes a string and feeds it into the interpreter.

For some reason I didn't see that he'd said, "during compilation". Perl is an interpreted language, so there's no compilation stage. A compiled language is modified in this way using a preprocessor. It doesn't really make sense to claim it's possible to inject code during compilation, that's the entire purpose of a compiler, to generate machine code from a syntax tree.

But code generation and execution during runtime, which is what I think you meant, is capable in any language with eval().

Perl is an interpreted language, so there's no compilation stage.

Perl claims to have a compilation stage, by which the documentation means that the lexer and parser produce an optree, which the runtime phase traverses. During that compilation stage, it's possible to run code which changes how the parser will treat subsequent syntactic elements.

Reply on news.ycombinator.com