Chris Kuklewicz: >Stefan Karrmann wrote: >> Dear all, >> >> can ghc compile huge tables into efficient code if they are constant at >> compile time? >> >> Two examples may clearify the question: >> >> big1 :: UArray Int Char >> big1 = array (0,1000) $! map (\i -> (i,toEnum i)) [0..1000] >> >> big2 = sum [0..10000]::Int -- == 50005000 == n*(n+1)/2 where n = 10000 >> > >GHC does not compute such values are compile time because >*) The computation may not finish in reasonable time (infinite/not halting) >*) The computation may generate a run-time error and crash the compilation >(divide by zero, pattern march failure, etc.) >*) Haskell is supposed to be lazy, things are computed when needed, not before
Does this mean that GHC does not evaluate constant subexpressions at compile-time? Or does it evaluate only some subclass of surely terminating and non-erroneous subexpressions at compile-time? Constant subexpression evaluation is a common compiler optimization technique, so I would be a bit surprised if GHC does not do it. Björn LIsper _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
