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Comment by distcs | Hacker News Reader

> Some languages (e.g. lisps) are deceptively small by relying on macros that form a "second-order" language that interacts with the "first-order" language, but Zig doesn't have that.

What are some other examples of such languages that rely on second-order languages? You mentioned Lisps. Would Forth be another example? Are there more examples?

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I think Ruby is sometimes used in a way that looks second-order. It allows so much metaprogramming that you can really make a full DSL. For example, RSpec:

   describe "order" do
     it "is marked as complete" do
       expect(@order).to be_complete
     end

     it "is not yet shipped" do
       expect(@order).not_to be_shipped
     end
   end

C++ templates. Also the rich type-level language in languages like Idris (these are qualitatively different, but I'd say they're another example of a second-language-within-a-language that operates at a different level of objects).

If type level functions are a "second language", then so is Zig's comptime.

It's not. comptime reifies types as regular objects (pretty much like maps), so you're not working at the type level; it's no more of a second language than reflection in Java. Of course, you cannot express things like the famous vector concatenation that's expressible with dependent types (https://gist.github.com/cbiffle/82d15e015ab1191b73c3) (unless the vector sizes are known at compile time, obviously).

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