Am Sonntag, 8. Januar 2006 15:45 schrieben Sie:
Daniel Fischer wrote:
Cool. So let's see if I got it. If I have
n <- readIO ... mapM_ (func n) list ...
in my programme, the runtime system will/might build object code for func n that is then used instead of using the general code for func and supplying both arguments to that?
That'd be wow, triple wow! And run-time compilation is a fitting name for that.
Well, it's possible to do that. But I don't know of any Haskell implementation that does. Sure, you might get a little bit of that if func is defined suitably, like func 0 = foo func 1 = bar func n = baz Implementations that have the "full laziness" property will handle one argument at a time to a function, and may do some work with just one argument to func. But it's nothing like having real run-time code generation.
-- Lennart
So back to square one. What then _is_ run-time compilation? Bulat said that in n <- readIO flip mapM [1 .. 100] $ \x -> print (x^n) the programme could insert (if, e.g. the value read is 2) the concrete faster algorithm for x^n. Isn't that some sort of run-time code generation? And a) how far might one expect that sort of thing done, b) how could one cajole the system to do that. Last, reverting to the search/replace example, if I have the general algorithm and also declare the function work :: String -> String work = searchReplace "pattern" "substitution", the compiler would produce specialised object code for that, or wouldn't it? Cheers, Daniel