Try swap p = (snd p, fst p)
or, equivalently swap ~(x,y) = (y,x) -- ryan On Tue, Nov 1, 2011 at 1:30 PM, Captain Freako <capn.fre...@gmail.com>wrote: > Hi John, > > I'm trying to use the GHCI debugger on this code: > > 20 instance ArrowLoop SF where > 21 loop (SF f) = SF $ \as -> > 22 let (bs, cs) = unzip (f (zip as (stream cs))) in bs > 23 where stream ~(x:xs) = x : stream xs > 24 > 25 swap :: (a,b) -> (b,a) > 26 swap (x,y) = (y,x) > > in order to watch the recursion of the `loop' function unfold. > However, when I single step through the code, I never stop on line 22 > (where I could, presumably, peek in at `bs' and `cs', in order to see > them develop): > > *SF> :break swap > Breakpoint 1 activated at SF.hs:26:1-18 > *SF> runSF (loop (arr swap)) [1,2,3] > Stopped at SF.hs:26:1-18 > _result :: (b, a) = _ > [SF.hs:26:1-18] *SF> :step > Stopped at SF.hs:26:14-18 > _result :: (b, a) = _ > x :: a = _ > y :: b = _ > [SF.hs:26:14-18] *SF> : > [1Stopped at SF.hs:23:34-42 > _result :: [a] = _ > xs :: [a] = _ > [SF.hs:23:34-42] *SF> : > Stopped at SF.hs:23:13-42 > _result :: [a] = _ > [SF.hs:23:13-42] *SF> : > Stopped at SF.hs:23:30-42 > _result :: [a] = _ > x :: a = _ > xs :: [a] = _ > [SF.hs:23:30-42] *SF> : > (Pattern repeats.) > > Do you have any advice? > > Thanks, > -db > > > > On Mon, Oct 31, 2011 at 3:19 PM, John Lask <jvl...@hotmail.com> wrote: > > On 1/11/2011 1:35 AM, Captain Freako wrote: > > > > you need to study ArrowLoop and understand that. In the code > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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