Thats great. Dynamic languages at say Java like speeds is a real game changer over the PHP/Rubylevel speeds. At the moment we only have LuaJIT proving its possible, but PyPy is the next contender.
Care to elaborate?
It does have dynamic typing, but that's not what it means to be a "dynamic language". Dynamic languages are late-bound; everything is up for grabs at runtime. In standard Scheme, this is true in the fairly useless sense that everything depends on the bindings in the global namespace, so you could in theory (set! car somethingweird), but this is very rarely practical; it almost serves only to make optimizing Scheme compilers difficult to write. Aside from that, the language leans much further toward early binding, doing things at compile-time, and using efficient data structures at the cost of flexibility.
In Scheme you can define and create new functions and macros at runtime. There is not much else that is dynamic about the Scheme standard[1] because... there's not much else to the Scheme standard.
As for reflection, I see that mainly as a tools/debugging aid, and therefore very implementation-specific stuff. "Dynamic" languages have reflection in their definition because they are mostly defined by implementation.
That said, the Scheme standard doesn't preclude reflectivity at all, nor seems particularly compile-oriented to me. Nowhere it is assumed that implementations be compilers at all.
I think most of the things you find missing there were not left out for efficiency, but because it was rightly considered that they don't belong in the language spec at all.
[1] By the "Scheme standard" I mean R5RS.
> As for reflection, I see that mainly as a tools/debugging aid
You can use it that way, but you can also use it for metaprogramming.
> "Dynamic" languages have reflection in their definition because they are mostly defined by implementation.
Plausible.
> That said, the Scheme standard doesn't preclude reflectivity at all, nor seems particularly compile-oriented to me. Nowhere it is assumed that implementations be compilers at all.
True.
Clojure 1.2.0 is already faster than Racket. Version 1.3.0 will probably bring it close to Go territory on those benchmarks.
For my own work I've found that getting Clojure in the Java ballpark is certainly possible.