Hello Dinko, Wednesday, November 29, 2006, 11:56:49 AM, you wrote:
How exactly can CSE cause space leaks, and what does this have to do with strictness?
standard example is x = [1..9] ++ [1..9] comparing to x = a++a where a=[1..9] first version runs (without CSE transformation) in fixed space, but computes [1..9] twice. second version computes its only once but needs more memory to hold results for second consumption. so, it's a classical space/time trade-off and lack of CSE transformation in such circumstances allow program to explicitly select whether he need better speed or space usage in the absence of laziness, entire a++a expression should be evaluated before return, so first version is no more able to tun in fixed space and second one definitely is winner so, in lazy environment, sometimes it's better to keep data in unevaluated form and compute it on each use, while in strict environment, CSE always win -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com