On 09/28/2014 09:43 AM, Travis Cardwell wrote:
On 2014年09月28日 16:42, PENG, BO YA wrote:
I'm trying to implement the arrow key functionality for a systemf REPL to recall previously entered lines. I think I should save the previous lines in a list and then traverse through the list when an arrow key is pressed, but I'm no sure how to detect an arrow key and implement this functionality. Can anyone give a brief description about the implementation or point me to some other resources? Thanks!
Perhaps readline would work for you?
http://hackage.haskell.org/package/readline
Cheers,
Travis _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
For keeping track itself, you can use something like a pointed list[1] pretty easily which frees you from having to keep track of indexes, looping around, going back and forth &c. I use it for quick-and-dirty selection in a menu in the game I'm writing. Once you have a way to get key presses, it becomes trivial (+ some lenses for clarity): whenM (keyPress KeyUp) $ screenState . maps %= C.previous whenM (keyPress KeyDown) $ screenState . maps %= C.next where ‘maps’ is my PointedList and C is Data.List.Pointed.Circular. [1]: http://hackage.haskell.org/package/pointedlist -- Mateusz K.