A generic merge function - 21 thoughts
[This post is literate Haskell, get the source here]When working with sorted lists you often come to the point where you want to combine two or more of them. This merge procedure forms the heart of merge sort it works something like:merge [1,3,4,5] [2,3,4] = [1,2,3,3,4,4,5] This merge function is not in the Haskell standard library, and even if there were, it might not be very useful.The problem i
Monads through Pictures
Introduction Monads in functional programming provide a framework for aspect-aware computations to be composed to build higher-level aspect-aware computations. An aspect-aware computation is some basic computation that has been enhanced, augmented, or, more generally, just transformed, to become aware of some generic concern. Consider, for example, the well-known maybe monad. This monad pr
Stefan Klinger
I consider myself a mathematically inclined computer scientist (PhD) with a knack for communicating technical insight. Currently I am employed with GSOC, west of Munich, evaluating and working on software in the ground segment, i.e., related to mission control. Interests I am particularly interested in the combinatorical and algorithmic aspects of software, functional programming and related resea
More Monads on the Cheap: Inlined fromMaybe
This article is about how to deal with null values. It follows up on this one. It’s intended for code stylists: people who care a lot about the difference between one line of code and two, or keeping control statements and temporary variables to a minimum. (A code stylist is kind of like the dual of a software architect, although one person can be both.) It’s not about code golf – although you mig
Playing with monad transformers
Yesterday someone posted a link to a great monad transformers tutorial. It's incredible. I think I finally start to understand (or at least being able to use) it. As part of testing my fresh knowledge I've written a simple virtual machine for a Forth-like language. Code (as usual - Literate Haskell, so you can just put it into .lhs file and run it) below. Enjoy! > module Main where > > import Cont
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スクリプト言語の比較
スクリプト言語の比較 *1 *2 *3 *4 *5 *6 *7 コメント 行の継続 定数 未代入の変数へのアクセス 変数の展開 入出力 出力 フォーマット出力 出力先変更 標準入力 __END__ 演算 +1 整数／整数 負数の除算 文字列 真と偽 多重代入 多岐分岐 関数 関数 関数引き数 関数引数に対する副作用 関数のデフォルト引数の値の評価タイミング 関数のデフォルト引数にコンテナ型を使用した場合の振舞 関数戻り値 関数の再帰 関数の別名 関数定義内関数定義 関数の引数の順番 関数にファイルハンドルを渡す オブジェクト指向 クラスの定義 インスタンスメソッドの定義 メソッドのクラス内での利用 インスタンスメソッドの可視性 インスタンスメソッドの追加 インスタンス変数 インスタンス変数の可視性 インスタンス変数の追加 クラス変数 クラスの継承 多重継承 スーパクラスのメソッド呼び出し
Real World Haskell
Why functional programming? Why Haskell? 1. Getting started 2. Types and functions 3. Defining types, streamlining functions 4. Functional programming 5. Writing a library: working with JSON data 6. Using typeclasses 7. Input and output 8. Efficient file processing, regular expressions, and file name matching 9. I/O case study: a library for searching the filesystem 10. Code case study: parsing a
Note on point-free programming style
Thu, 03 Jan 2008 Note on point-free programming style This old comp.lang.functional article by Albert Y. C. Lai, makes the point that Unix shell pipeline programming is done in an essentially "point-free" style, using the shell example: grep '^X-Spam-Level' | sort | uniq | wc -l and the analogous Haskell code: length . nub . sort . filter (isPrefixOf "X-Spam-Level") Neither one explicitly mentions
Composing Contracts
This document is an unofficial example implementation of the system originally described in the paper Composing contracts: an adventure in financial engineering, by Simon Peyton Jones, Jean-Marc Eber, and Julian Seward. Familiarity with both versions of this paper is assumed. This example implementation is a literate Haskell program, Contracts.lhs. Don't be put off by the embedded HTML — it is an
本物のプログラマはHaskellを使う：ITpro
筆者 shelarcy Haskellは，関数型プログラミングというジャンルに属する言語です。Haskellや関数型プログラミングを題材に物事を見ていくことで，今まで思いもよらなかったような未知の世界を知ることができるでしょう。 プログラミング言語を学ぶという行為には， 言語の基本的な文法や考え方を理解する 言語の文化圏で広く使われている考え方に親しんでその言語らしい書き方を習得する 単に言語を使ってできること以上の知恵を学ぶ の3段階があります。この連載では，三つ目の段階を目標に，Haskellプログラミングの世界を一つひとつ丁寧に紹介していきます。 更新は毎月第1水曜日（1月のみ第2水曜日）
ICS | Utrecht University
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Haskell/Understanding monads - Wikibooks, open books for an open world
There is a certain mystique about monads, and even about the word "monad" itself. While one of our goals of this set of chapters is removing the shroud of mystery that is often wrapped around them, it is not difficult to understand how it comes about. Monads are very useful in Haskell, but the concept is often difficult to grasp at first. Since monads have so many applications, people often explai
Some Playing with Derivatives
This is a summary of what I’ve been playing with in case people find it interesting. In general, there are three ways to find the derivative of a function: Do the symbolic manipulation of formulae that we all learned in school when we were 16 years old. This assumes that one has the function as an algebraic expression of some kind in terms of known quantities. Do it numerically, by computing (f(x
Survey: Haskell Unicode support
Haskell source is interpreted as UTF-8, but internally the data is stored as Unicode code points. However the generic show method does not s...
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http://www.kennknowles.com/blog/2007/12/20/infinite-lazy-knuth-bendix-completion-for-monoids-in-haskell/
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