travisbrown

/**
 * We can use the Scala type system (with help from Miles Sabin's Shapeless
 * library) to solve the bank account number validation problem in the second
 * user story of the KataBankOCR kata on Coding Dojo:
 * 
 * http://codingdojo.org/cgi-bin/wiki.pl?KataBankOCR
 * 
 * By Travis Brown in response to a question by Paul Snively on the Shapeless
 * Dev mailing list:
 *

snoyberg

Many of us use the OverloadedStrings language extension on a regular basis. It provides the ability to keep the ease-of-use of string literal syntax, while getting the performance and correctness advantages of specialized datatypes like ByteString and Text. I think we can get the same kind of benefit by allowing another literal syntax to be overloaded, namely lists.

Overly simple approach

The simplest example I can think of is allowing easier usage of Vector:

[1, 2, 3] :: Vector Int

In order to allow this, we could use a typeclass approach similar to how OverloadedStrings works:

gregorycollins

{-# LANGUAGE OverloadedStrings, MagicHash, UnboxedTuples, BangPatterns #-}

import           Control.Monad          (replicateM_)
import           Criterion.Main         (defaultMain, bench, whnfIO)
import qualified Data.ByteString        as S
import qualified Data.ByteString.Char8  as S8
import           Data.ByteString.Unsafe (unsafePackAddressLen, unsafeUseAsCStringLen)
import qualified Data.Char
import           Data.Char              (ord)
import qualified Data.Word8

sebastiaanvisser

{-# LANGUAGE
    GADTs
  , KindSignatures
  , RankNTypes
  , TupleSections
  , TypeOperators
  #-}
module Generics.Morphism where

import Control.Arrow

tonymorris

case class ListZipper[+A](lefts: List[A], x: A, rights: List[A]) {
  def map[B](f: A => B): ListZipper[B] =
    sys.error("todo")

  // map with zipper context
  def coFlatMap[B](f: ListZipper[A] => B): ListZipper[B] =
    sys.error("todo")

  def findRight(p: A => Boolean): Option[ListZipper[A]] =
    sys.error("todo")

manuel

;; Error monad from Filinski's "Representing Monads"
(define *default-prompt* (make-prompt))

(define (reflect m) (shift *default-prompt* k (ext k m)))

(define (reify t) (push-prompt *default-prompt* (unit (t))))

(define-record-type Success
  (make-success a)
  success?

coreyhaines

Write a system that evolves a 100 x 100 grid of cells
to the next generation according to the following rules.

1) Any living cell with less than 2 live neighbors dies
2) Any living cell with 2 or 3 live neighbors stays alive
3) Any living cell with more than 3 live neighbors dies
4) Any dead cell with exactly 3 lives neighbors comes to life

Note: A cell has 8 neighbors
...

coreyhaines

Create a system that will convert a numeric value to an 3x5 LED display.
...
...
...
...
...


Feature: Generating LCD representation for single numbers

tonyg

#lang racket/base

(define tasklist (list (list 'root (box 'no-continuation))))
(define currtask tasklist)

(define call/cc call-with-current-continuation)

(define fork
    (lambda (name)
        (call/cc

swannodette

;; based on core.logic 0.8-alpha2 or core.logic master branch

(ns sudoku
  (:refer-clojure :exclude [==])
  (:use clojure.core.logic))

(defn get-square [rows x y]
  (for [x (range x (+ x 3))
        y (range y (+ y 3))]
    (get-in rows [x y])))