Re:How to make Lisp go faster than C [pdf]
by martincmartin on Sunday May 30, 2010 @04:20PM
(#1391054)
Yes. The Common Lisp spec says you can put declarations a lot of places, including prog:
http://clhs.lisp.se/Body/s_declar.htm
So you can basically wrap it around any S-expression you want.
When I was at ITA we did that a lot. For example, there was a macro i+ that would expand to basically "the two arguments are fixnums, as is the result. Now, please give me the sum."
In debug builds, the type declarations would be come assertions. In release builds, they'd become assumptions, i.e. the whole thing would compile to a single x64 ADD instruction.
The paper says that to get the speed they had to turn off run time type checking, but they say "here's how to do it globally" does that mean you can turn of type checking in just one module or function?