Normandy, Tennessee and Haskell: Difference between pages

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[[Image:Haskell Logo.jpg|frame|Haskell logo]]
'''Normandy''' is a town located in [[Bedford County, Tennessee]]. As of the [[2000]] census, the town had a total population of 141.
 
'''Haskell''' is a standardized [[purely functional|pure]] [[functional_programming|functional]] [[programming language]] with [[non-strict programming language|non-strict semantics]]. Named after the logician [[Haskell Curry]], it was created by a committee formed in [[1987]] for the express purpose of defining such a language. The direct predecessor of Haskell was [[Miranda programming language|Miranda]] from [[1985]].
== Geography ==
The latest semi-official language standard is '''Haskell 98''', intended to specify a minimal, portable version of the language for teaching and as a base for future extensions.
[[Image:TNMap-doton-Normandy.PNG|right|Location of Normandy, Tennessee]]
The language continues to evolve rapidly, with [[Hugs]] and [[Glasgow Haskell Compiler|GHC]] (see below) representing the current [[de facto#De facto standards|''de facto'' standard]].
Normandy is located at 35&deg;27'8" North, 86&deg;15'31" West (35.452249, -86.258714)[[Geographic references|<sup>1</sup>]].
 
Characterizing syntax features in Haskell include [[pattern matching]], [[currying]], [[list comprehension]]s, [[guard (computing)|guard]]s, and definable [[operator (programming)|operator]]s. The language also supports [[recursion|recursive]] functions and [[algebraic data type]]s, as well as [[lazy evaluation]]. Unique concepts include [[Monads_in_functional_programming|monad]]s, and [[type class]]es.
According to the [[United States Census Bureau]], the town has a total area of 0.6 [[square kilometer|km&sup2;]] (0.2 [[square mile|mi&sup2;]]). 0.6 km&sup2; (0.2 mi&sup2;) of it is land and none of the area is covered with water.
The combination of such features can make [[function (programming)|functions]] which would be difficult to write in a procedural programming language almost trivial to implement in Haskell.
 
The language is, as of [[as of 2002|2002]], the [[Lazy_evaluation|lazy]] [[functional programming language|functional language]] on which the most research is being performed. Several variants have been developed: parallelizable versions from [[Massachusetts Institute of Technology|MIT]] and [[Glasgow University|Glasgow]], both called Parallel Haskell; more parallel and distributed versions called Distributed Haskell (formerly Goffin) and [[Eden_programming_language|Eden]]; a [[speculative execution|speculatively evaluating]] version called Eager Haskell and several [[object orientation|object oriented]] versions: Haskell++, [[O'Haskell]] and [[Mondrian programming language|Mondrian]].
== Demographics ==
As of the [[census]] of [[2000]], there are 141 people, 53 households, and 35 families residing in the town. The [[population density]] is 236.7/km&sup2; (615.1/mi&sup2;). There are 60 housing units at an average density of 100.7/km&sup2; (261.7/mi&sup2;). The racial makeup of the town is 98.58% [[White (U.S. Census)|White]], 0.00% [[African American (U.S. Census)|African American]], 0.71% [[Native American (U.S. Census)|Native American]], 0.00% [[Asian (U.S. Census)|Asian]], 0.00% [[Pacific Islander (U.S. Census)|Pacific Islander]], 0.00% from other races, and 0.71% from two or more races. 0.71% of the population are [[Hispanic (U.S. Census)|Hispanic]] or [[Latino (U.S. Census)|Latino]] of any race.
 
Although Haskell has a comparatively small user community, its strengths have been well applied to a few projects. [[Autrijus Tang]]'s [[Pugs]] is an implementation for the forthcoming Perl 6 language with an interpreter and compilers that proved useful already after just a few months of its writing. [[DARCS]] is a revision control system, with several innovative features.
There are 53 households out of which 34.0% have children under the age of 18 living with them, 45.3% are married couples living together, 13.2% have a female householder with no husband present, and 32.1% are non-families. 32.1% of all households are made up of individuals and 11.3% have someone living alone who is 65 years of age or older. The average household size is 2.66 and the average family size is 3.19.
 
There is also a Haskell-like language that offers a new method of support for [[GUI]] development called [[Clean programming language|Concurrent Clean]]. Its biggest deviation from Haskell is in the use of [[uniqueness type]]s for input as opposed to [[Monads in functional programming|monads]].
In the town the population is spread out with 27.0% under the age of 18, 13.5% from 18 to 24, 29.8% from 25 to 44, 23.4% from 45 to 64, and 6.4% who are 65 years of age or older. The median age is 34 years. For every 100 females there are 110.4 males. For every 100 females age 18 and over, there are 98.1 males.
 
== Examples ==
The median income for a household in the town is $40,938, and the median income for a family is $48,125. Males have a median income of $31,429 versus $18,036 for females. The per capita income for the town is $17,729. 8.8% of the population and 3.2% of families are below the poverty line. Out of the total people living in poverty, 18.6% are under the age of 18 and 0.0% are 65 or older.
 
[[Category:Bedford County, Tennessee]]
=== Anatomy of a Haskell function ===
 
The [[Hello world program|"Hello World"]] of functional languages is the [[factorial]] function. Expressed as pure Haskell:
 
fac :: Integer -> Integer
fac 0 = 1
fac n | n>0 = n * fac (n-1)
 
This describes the factorial as a recursive function, with a single terminating base case. It is similar to the descriptions of factorials found in mathematics textbooks. Much of Haskell code is similar to mathematics in facility and syntax.
 
The first line of the factorial function shown is optional, and describes the ''types'' of this function. It can be read as ''the function fac'' (fac) ''has type'' (::) ''from integer to integer'' (Integer -> Integer). That is, it takes an integer as an argument, and returns another integer.
 
The second line relies on [[pattern matching]], an important part of Haskell programming. Note that parameters of a function are not in parentheses but separated by spaces. When the function's argument is 0 (zero) it will return the integer 1 (one). For all other cases the third line is tried. This is the [[recursion]], and executes the function again until the base case is reached. A [[guard (computing)|guard]] protects the third line from negative arguments that would run down unterminated.
 
The "Prelude" is a number of small functions analogous to C's standard library. Using the Prelude and writing in the "point free" (insert classic Haskell joke here) style of unspecified arguments, it becomes:
 
fac = product . enumFromTo 1
 
The above is close to mathematical definitions such as ''f = g <small>o</small> h'' (see [[function composition]]), and indeed, it's ''not'' an assignment of a value to a variable.
 
=== More complex examples ===
 
A simple [[RPN]] calculator:
 
calc = foldl f [] . words
where
f (x:y:zs) "+" = y+x:zs
f (x:y:zs) "-" = y-x:zs
f (x:y:zs) "*" = y*x:zs
f (x:y:zs) "/" = y/x:zs
f xs y = (read y :: Float):xs
 
A function which returns a stream of the [[Fibonacci numbers]] in linear time:
 
fibs = 0 : 1 : (zipWith (+) fibs (tail fibs))
 
The same function, presented with GHC's [[parallel list comprehension]] syntax:
 
fibs = 0 : 1 : [ a+b | a <- fibs | b <- tail fibs ]
 
The earlier factorial function, this time using a sequence of functions:
 
fac n = (foldl (.) id [\x -> x*k | k <- [1..n]]) 1
 
A remarkably concise function that returns the list of [[Hamming number]]s in order:
 
hamming = 1 : map (*2) hamming # map (*3) hamming # map (*5) hamming
where xxs@(x:xs) # yys@(y:ys)
| x==y = x : xs#ys
| x<y = x : xs#yys
| x>y = y : xxs#ys
 
== Implementations ==
The following all comply fully, or very nearly, with the Haskell 98 standard, and are distributed under [[open source]] licences. There are currently no commercial Haskell implementations.
* '''''[[Hugs]]''''' ([http://www.haskell.org/hugs/]) is a [[bytecode]] interpreter. It offers fast compilation of programs and reasonable execution speed. It also comes with a simple graphics library. Hugs is good for people learning the basics of Haskell, but is by no means a "toy" implementation. It is the most portable and lightweight of the Haskell implementations.
* '''''[[Glasgow Haskell Compiler|Glasgow Haskell Compiler]]''''' ([http://www.haskell.org/ghc/]). The Glasgow Haskell Compiler compiles to native code on a number of different architectures, and can also compile to C. GHC is probably the most popular Haskell compiler, and there are quite a few useful libraries (e.g. bindings to [[OpenGL]]) that will only work with GHC.
* '''''nhc98''''' ([http://www.cs.york.ac.uk/fp/nhc98/]) is another bytecode compiler, but the bytecode runs significantly faster than with Hugs. Nhc98 focuses on minimising memory usage, and is a particularly good choice for older, slower machines.
* '''''Jhc''''' ([http://repetae.net/john/computer/jhc/]) a haskell compiler emphasising speed and efficiency of generated programs as well as exploration of new program transformations.
* '''''Gofer''''' An educational version of Haskell, Gofer was developed by Mark Jones. It was supplanted by HUGS.
* '''''HBC''''' ([http://www.cs.chalmers.se/~augustss/hbc/hbc.html]) is another native-code Haskell compiler. It hasn't been actively developed for some time, but is still usable.
*'''''Helium''''' ([http://www.cs.uu.nl/helium/]) is a newer dialect of Haskell. The focus is on making it easy to learn. It currently lacks typeclasses, making it incompatible with many Haskell programs.
 
== Extensions ==
*[[O'Haskell]] is an extension of Haskell adding [[object-oriented programming|object-orientation]] and [[concurrent programming]] support.
 
== External links ==
* [http://www.haskell.org The Haskell Home Page]
* [http://www.haskell.org/hawiki/ The Haskell Wiki]
* [http://www.haskell.org/tutorial/ A Gentle Introduction to Haskell 98] ([http://www.haskell.org/tutorial/haskell-98-tutorial.pdf pdf] format)
* [http://haskell.org/papers/NSWC/jfp.ps Haskell vs. Ada vs. C++ vs. Awk vs. ... An Experiment in Software Prototyping Productivity]
* [http://www.willamette.edu/~fruehr/haskell/evolution.html The Evolution of a Haskell Programmer] - a slightly humorous overview of different programming styles available in Haskell
* [http://haskell.readscheme.org An Online Bibliography of Haskell Research]
* [http://www.haskell.org/humor/press.html Haskell Humor]
* [http://www.research.microsoft.com/~simonpj/papers/haskell-retrospective Wearing the hair shirt: a retrospective on Haskell]. Simon Peyton Jones, invited talk at POPL 2003.
 
{{Major programming languages small}}
 
[[Category:Haskell dialects|*]]
[[Category:Programming languages]]
[[Category:Functional languages]]
[[Category:Declarative programming languages]]
 
[[cs:Haskell]]
[[de:Haskell (Programmiersprache)]]
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[[fr:Haskell]]
[[it:Haskell]]
[[nl:Haskell]]
[[ja:Haskell]]
[[pl:Haskell]]
[[pt:Haskell (linguagem de programação)]]
[[ru:Haskell]]
[[sk:Haskell (programovací jazyk)]]
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