Daniel Fischer wrote:
On Thursday 03 February 2011 23:19:31, Johan Tibell wrote:
Hi,
For what it's worth I saw the problems in your counting examples right away, without reading the explanatory text below.
Yes, they were pretty obvious with enough experience. For beginners I expect it to be a rather insidious trap.
Hopefully that means that it's possibly to learn how to spot such things without resorting to e.g. running the program or reading Core *gasp*.
Within limits. Detrimental laziness or strictness can be arbitrarily well hidden.
I am a relative newcomer to Haskell, but I think I have a reasonable understanding of the executaion model. Enough to fix performance issues in simple code like the example given. However, one of the Haskell projects I work on is Ben Lippmeier's DDC compiler. Thats about 50000 lines of Haskell code and finding performance issues there is really difficult. Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/