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Implementation of the Jobs Puzzle in Curry

by Sebastian Fischer, January 2015

Verbal problem description

There are four people: Roberta, Thelma, Steve, and Pete.

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Die RubyKara Erweiterung aus Kiel gibt es jetzt hier: https://github.com/sebfisch/rubykara-kiel

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A Dialog on How to Manage Patches with Darcs

Fred: So, you know Darcs?

Lisa: Sure.

Fred: I heard it is quite flexible in managing patches. Wanna show me?

Lisa: Ok, let's make a new repository for some imaginary project.

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{- 

A German blog post translating Java code for the build tool Ant to Scala

    http://funktionale-programmierung.de/2013/02/26/scala-java-ant.html

made me translate the Scala code to Haskell. I added combinators for binary
composition of mappers as well as a unit mapper for one of them. The code is
still shorter. I find the Haskell version more readable because expressions
and their types are separate rather than interleaved as in Scala.

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Comparing Snap's and Yesod's Template Languages Heist and Hamlet - and HSP

Currently, Snap and Yesod are the two most active web frameworks for Haskell. In this document, I compare the template languages used by those frameworks for generating HTML.

Both template languages let programmers write markup directly in a markup language rather than generating it from within Haskell. Compared with static HMTL, template languages support substitution to dynamically determine parts of the content of the generated page.

[Heist] and [Hamlet] support different constructs to generate content dynamically. They also differ regarding their syntax for static content.

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#!/bin/bash

# Replaces classes in Android Package Files
# (c) Sebastian Fischer, CC-BY

# Can be used to rebuild an App with a modified version of a used library,
# as required for closed works that link to an LGPL library.

# Depends on: https://code.google.com/p/dex2jar/

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Delimited Continuations

Delimited continuations manipulate the control flow of programs. Similar to control structures like conditionals or loops they allow to deviate from a sequential flow of control.

We use exception handling as another example for control flow manipulation and later show how to implement it using delimited continuations. Finally, we show that nondeterminism can also be expressed using delimited continuations.

Exception Handling

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module ListTransformer where

import Control.Applicative

import Control.Arrow
import Control.Category
import Prelude hiding ( id, (.) )

data ListConsumer a b
  = Done b

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tyFun : Set -> Set -> Set;
tyFun A T = A -> T;

using (G:Vect Set n) {

  data Expr : Vect Set n -> Set -> Set where
    Var : (i:Fin n) -> Expr G (vlookup i G)
  | Val : T -> Expr G T
  | Lam : Expr (A::G) T -> Expr G (tyFun A T) -- using `A -> T` directly fails
  | App : Expr G (A -> T) -> Expr G A -> Expr G T

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example from

    http://blog.downstairspeople.org/2010/06/14/a-brutal-introduction-to-arrows/

rewritten using Applicative instance from

    http://cdsmith.wordpress.com/2011/07/30/arrow-category-applicative-part-i/