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December 2014

48 participants
22 discussions

Use Lens to manipulate Data.Tree
by Zach Moazeni 07 Dec '14

07 Dec '14

Hello, I'm trying to understand how I would manipulate a Data.Tree in Haskell. I came across this StackOverflow answer and accompanying blog post, but it doesn't run locally for me: * http://stackoverflow.com/a/15489761/410759 * https://www.fpcomplete.com/user/davorak/code-snippets/zipper-tree-examples Here's a gist with the code and the error I'm seeing: https://gist.github.com/zmoazeni/0049f3ab365ae600b131 I just want to start slow and be able to do three actions: * add +10 to all values in the tree * add a node to an existing node's subForest * remove a node (along with its subForest) from the tree I understand that this won't actually "edit in place" and my code would need to call a function which would return an updated version of the original tree. Finally, Lens wasn't my first choice. I was trying to understand Zippers from http://learnyouahaskell.com/zippers and my brain seized. I'm just falling back to Lens because it seems like the simplest/dsl-ish way to manipulate structures like this. Thanks for any help! -Zach

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haskell Time
by Claudia Weber 01 Dec '14

01 Dec '14

Hi guys, I'm new to Haskell and I'm just trying out some easy functions right now, but I'm having some trouble here... I want to display a clock type Time = (Int, Int) (hoursx,minutesy) x ={0,1,...,23} y={0,1,...,59} where I can add hours and minutes or set back time. If its 23,58 for example and I want to add 35 minutes, the clock has to set to 0,33 not 24,23. Because I'm just getting started with Haskell, I have nooo idea what to do. Would be great if someone could help me out with this :) --- Alle Postfächer an einem Ort. Jetzt wechseln und E-Mail-Adresse mitnehmen! Rundum glücklich mit freenetMail

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