On Fri, Mar 6, 2009 at 1:48 AM, Daryoush Mehrtash <dmehrt...@gmail.com>wrote:
> Question: Do I need to worry about space leak if I am using the fix to > instead of the "let"? If you need to worry about a space leak with fix, you need to worry about it with let. The reason arrows can tie the loop tighter is more about the nature of recursion in streams; an arrow "sees" that prior values of a signal are not used, whereas value recursion is much less restricted. If, for example, the arrow were a kleisli arrow over the list monad, this would not be possible. With the definition fix f = let x = f x in x, you should not see any performance difference, other than the standard HOF penalty if there is not enough inlining... but that should not be asymptotic anyway. Luke > > Thanks > > Daryoush > 2009/3/5 Luke Palmer <lrpal...@gmail.com> > >> On Thu, Mar 5, 2009 at 6:27 PM, Donn Cave <d...@avvanta.com> wrote: >> >>> Quoth Jonathan Cast <jonathancc...@fastmail.fm>: >>> >>> > You can certainly use let: >>> > >>> > reader <- forkIO $ let loop = do >>> > (nr', line) <- readChan chan' >>> > when (nr /= nr') $ hPutStrLn hdl line >>> > loop >>> > in loop >>> > >>> > But the version with fix is clearer (at least to people who have fix in >>> > their vocabulary) and arguably better style. >>> >>> Would you mind presenting the better style argument? To me, the >>> above could not be clearer, so it seems like the version with fix >>> could be only as clear, at best. >> >> >> I like using fix when it's simple rather than let, because it tells me the >> purpose of the binding. eg., when I see >> >> let foo = ... >> >> Where ... is fairly long, I'm not sure what the purpose of foo is, or what >> its role is in the final computation. It may not be used at all, or passed >> to some modifier function, or I don't know what. Whereas with: >> >> fix $ \foo -> ... >> >> I know that whatever ... is, it is what is returne, and the purpose of foo >> is to use that return value in the expression itself. >> >> I know that it's a simple matter of scanning to the corresponding "in", >> but let can be used for a lot of things, where as fix $ \foo is basically >> only for simple knot-tying. Now, that doesn't say anything about the use of >> fix without an argument (passed to an HOF) or with a tuple as an argument or >> many other cases, which my brain has not chunked nearly as effectively. I >> think fix is best with a single, named argument. >> >> Luke >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe@haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> > >
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe