https://wiki.haskell.org/api.php?action=feedcontributions&user=TillmannRendel&feedformat=atomHaskellWiki - User contributions [en]2020-11-24T12:42:10ZUser contributionsMediaWiki 1.27.4https://wiki.haskell.org/index.php?title=User_groups&diff=55713User groups2013-04-15T10:24:08Z<p>TillmannRendel: /* Germany */ Add Frankfurt Haskell User Group</p>
<hr />
<div>[[Category:Community]]<br />
<br />
A range of Haskell User Groups are springing up all over.<br />
<br />
== Online communities ==<br />
* [http://www.reddit.com/r/haskell/ Haskell Reddit]<br />
* [http://stackoverflow.com/questions/tagged?tagnames=haskell Haskell on Stack Overflow]<br />
<br />
== User groups ==<br />
<br />
Regular meetings in a particular geographical area. Great if you want to see and meet other Haskellers.<br />
<br />
===North America===<br />
<br />
====West Coast ====<br />
<br />
;[http://socalfp.blogspot.com/ SoCal FP Group]<br />
<br />
;[http://bayfp.org/ The Bay Area Functional Programmers group]<br />
:Meeting monthly in the San Francisco Bay area. See [http://bayfp.org/blog their blog] for more details and news of upcoming meetings.<br />
<br />
;[http://pdxfunc.org PDXfunc: Portland FP Group]<br />
:Monthly meetings of the Portland, Oregon functional programming group. Meetings occur on the second Monday of each month at 7 pm, typically in Downtown/NW Portland.<br />
<br />
;[http://www.haskell.org/pipermail/haskell-cafe/2008-February/038991.html Seattle: Northwest Functional Programming Interest Group]<br />
:a Northwest Functional Programming Interest Group in Seattle.<br />
<br />
;[http://www.meetup.com/Vancouver-Haskell-Unmeetup/ Vancouver Haskell UnMeetup]<br />
:Monthly interactive sessions, (+10) for joining<br />
<br />
====East Coast====<br />
<br />
;[http://groups.google.com/group/bostonhaskell Boston Haskell Users' Group].<br />
:Meets monthly.<br />
<br />
;[http://www.meetup.com/NY-Haskell/ New York Haskell Users Group]<br />
:The NY Haskell Users Group is for all programmers either interested in or experienced with the Haskell programming language. Meets monthly.<br />
<br />
;[http://www.meetup.com/lisp-59/ New York Functional Programmers]<br />
:Come and meet like-minded functional programmers in the New York area.<br />
<br />
;[http://www.lisperati.com/fringedc.html FringeDC Washington]<br />
:Meetings about functional programming languages in Washington DC.<br />
<br />
;[http://groups.google.com/group/AFPUG Atlanta Functional Programming Users Group]<br />
:Meet other functional programmers in the Atlanta area. Join us and geek out!<br />
<br />
;Toronto Haskell User Group<br />
:Haskellers of Toronto, unite! We meet at [http://hacklab.to hacklab.to] on the second Wednesday of every month! There is also a small organizational [http://groups.google.com/group/toronto-haskell/ mailing list] you can join to keep up to date.<br />
<br />
;[https://groups.google.com/forum/?fromgroups#!forum/haskellers-montreal Montreal Haskell Users' Group].<br />
:Meets monthly.<br />
<br />
====Central====<br />
<br />
;[http://leibnizdream.wordpress.com/2007/12/22/new-austin-functional-programmers-group-in-2008/ Austin Functional Programmers Group]<br />
:See the [http://groups.google.com/group/austin-fp discussion group] for more.<br />
<br />
;[http://groups.google.com/group/real-world-haskell-book-club/browse_thread/thread/3e8e59768c8c50a9 Colorado Area Haskell Study Group]<br />
<br />
;[http://groups.google.com/group/haskell-chicago Chicago Haskell User Group] — new group, had first general meeting in December 2009; meeting every other month.<br />
<br />
;[http://www.meetup.com/DenHUG/ Denver Area Haskell Users Group] -- DenHUG had it's first meeting on 27 Feb 2010. Next meeting will be 3 Apr 2010.<br />
<br />
;[http://www.lambdalounge.org St. Louis Lambda Lounge] -- Meets the 1st Thursday of the month. Since Dec 2008, Lambda Lounge is a user group in St. Louis organized loosely around the idea of exploring dynamic and functional languages.<br />
<br />
===Australia===<br />
<br />
;[http://groups.google.com/group/fp-syd FP-SYD, the Sydney (Australia) Functional Programming group]<br />
:FP hackers in Sydney.<br />
<br />
;[http://sites.google.com/site/fpunion/ (FPU) Melbourne Functional Programming Union]<br />
:The FPU is a collective of functional programming language enthusiasts, which has been in operation since 1998. We are based at the University of Melbourne, in the Department of Computer Science and Software Engineering, but we are open to all members of the community. We meet on a regular basis for lively discussions on topics broadly associated with the declarative programming paradigm.<br />
<br />
;[http://bfpg.org/ Brisbane Functional Programming Group (BFPG)] ([http://www.meetup.com/Brisbane-Functional-Programming-Group-BFG/ Meetup page])<br />
:A group for Functional Programming with Haskell, Scala and other languages.<br />
<br />
;[http://meetup.com/PerthFP/ Perth Functional Programmers Meetup]<br />
:A group in Perth, WA for Functional Programming with Haskell, Scala and other languages.<br />
<br />
===Europe===<br />
<br />
==== UK ====<br />
;[http://www.meetup.com/hoodlums/ Hoodlums - Haskell developer meetup]<br />
:Meets monthly on the second Thursday of the month in Canary Wharf. It is a "Coding Dojo" format where we pick some interesting problem and solve it as a group. <br />
<br />
;[http://www.meetup.com/London-HUG/ London Haskell User Group]<br />
:The main meetings are monthly on the last or fourth Thursday of the month. The group was revived in late 2012.<br />
<br />
;[http://www.meetup.com/ed-lambda/ ed lambda (Edinburgh, UK)]<br />
:For functional programming in general, founded by a Haskeller. First meeting will be September 13th 2010.<br />
<br />
;[http://groups.google.com/group/oxhug OxHUG - the Oxford Haskell Users Group]<br />
:Meets every other week, currently at the Department of Computer Science, University of Oxford. Discussion session followed by adjournment to a local tavern. Aimed at students, graduates, professionals and enthusiasts.<br />
<br />
;[http://groups.google.com/group/fp-southwales fp-southwales], the South Wales Functional Programming User Group<br />
:Starting up in late 2009, based out of Swansea University.<br />
<br />
==== France ====<br />
<br />
;[[Fr/Haskell]]<br />
:The Strasbourg HUG meets monthly in an informal setting. Level is very low and newbies are very welcome.<br />
<br />
==== Netherlands ====<br />
<br />
;[http://dutchhug.nl/ Dutch HUG]<br />
:The Dutch HUG meets monthly in an informal setting.<br />
<br />
==== Belgium ====<br />
<br />
;[[Ghent Functional Programming Group]]<br />
:The Ghent Functional Programming Group will be having its first meeting on April 1, 2010.<br />
<br />
==== Germany ====<br />
<br />
;Haskell in Frankfurt<br />
: <ul><li>[http://www.meetup.com/Frankfurt-Haskell-User-Group Frankfurt Haskell User Group] meets monthly.</li><li> [http://wiki.lug-frankfurt.de/Programmierworkshop/aktuell Regular Saturday Workshop] taking place every couple of months. Feel free to join us!</li><br />
<br />
;[http://www.iba-cg.de/hal5.html Haskell in Leipzig]<br />
:Hal, they have videos [http://iba-cg.de/haskell.html online].<br />
<br />
;[http://www.haskell-munich.de Haskell in Munich]<br />
: We had our first meeting on Thursday, 29th of September 2011. We are always looking forward to see new people. If you can make it to Munich, consider joing us!<br />
<br />
''If anyone is interested in a user group in '''Ulm, Germany''' please let me know ([[HugUlm]]).''<br />
<br />
''If someone is interested in a user group in '''Mannheim or Heidelberg, Germany''', please let me know (user cgo [[http://www.haskell.org/haskellwiki/?title=Special:Emailuser&target=Cgo]] in this Wiki). Or<br />
if there is one which is not listed here, please let me know too!<br />
<br />
==== Switzerland ====<br />
<br />
;[http://www.meetup.com/HaskellerZ/ Haskell User Group Zurich]<br />
:We are meeting once a month to share knowledge of and experience with Haskell.<br />
<br />
==== Italy ====<br />
;[[ItaloHaskell]]<br />
:We had a first meeting in August 2008 and we are planning a second one sometime during the 2008/2009 Autumn/Winter season.<br />
<br />
==== Iceland ====<br />
<br />
;[[Reykjavik Haskell User Group]] Iceland<br />
;[http://groups.google.com/group/haskell-is Currently recruiting members]<br />
<br />
==== Poland ====<br />
;[http://wtf.humane-software.com Warsaw Functional Society]<br />
:We met informally a few times before the 2012 summer vacation. We're starting up again in September 2012. <br>Check out our wiki and join us if you're in the area.<br />
<br />
==== Ukraine ====<br />
;[https://groups.google.com/forum/#!forum/ltu-kiev LtU-Kiev community]<br />
:Irregular meetups, usually with prepared talks on Haskell and other FP topics.<br />
;[http://ro-che.info/odhug Odessa Haskell User Group]<br />
:Regular informal meetups (approximately once a month) in a pub or cafe<br />
<br />
=== Israel ===<br />
<br />
;[[IsraelHaskell]] User Group<br />
:[http://article.gmane.org/gmane.comp.lang.haskell.cafe/28877 Are getting organised].<br />
<br />
=== Russia ===<br />
<br />
;[http://spbhug.folding-maps.org Saint-Petersburg Haskell User Group]<br />
;[https://groups.google.com/forum/#!forum/mskhug Moscow Haskell User Group]<br />
<br />
=== Turkey ===<br />
<br />
;[http://groups.google.com/group/core-haskell?lnk=srg Turkey Haskell Programmer's Group]<br />
:Formed by Turkish Functional Programmers, the group began to communicate via an e-mail list opened by core.gen.tr. The first contribution is hlibev project by Aycan iRiCAN.<br />
<br />
;[http://bilfp.wikidot.com/ BILFP (Bilkent University Comp. Eng. Dept. Functional Programming Society)] Turkey <br />
:Project aims to improve people's knowledge and encourage the use of functional programming languages &mdash; especially in Turkey. Group is open to functional-programming-related discussions and establishes related presentations at Bilkent University that are open to anybody.<br />
<br />
===South America===<br />
<br />
====Brazil====<br />
;[[User_groups/Brazil|Grupo Brasileiro de Usuários de Haskell]]<br />
: Grupo criado para reunir os desenvolvedores e entusiastas que utilizam Haskell no Brasil<br />
<br />
==== Bolivia ====<br />
; [http://comunidadhaskell.org Comunidad Haskell San Simon]<br />
: Haskell user group for Bolivia and spanish speaking community<br />
<br />
===Asia===<br />
<br />
;[http://lisp.org.cn/en/ China Lisp User Group]<br />
:China Lisp User Group (CLUG) is the earliest founded Lisp user group in China. <br />
<br />
;[http://www.starling-software.com/en/tsac.html Tokyo Society for the Application of Currying]<br />
<br />
===Africa===<br />
<br />
====South Africa====<br />
; [http://www.meetup.com/lambda-luminaries/ Lambda Luminaries] : Functional programming user group based in Centurion, Gauteng.<br />
<br />
== Workshops/meet ups ==<br />
<br />
Less regular, and move around. Usually have a few talks from invited speakers.<br />
See the [[Haskell]] homepage for a list of upcoming events.<br />
<br />
== Hackathons ==<br />
<br />
Getting together to squash bugs and write new stuff. For a list of past and upcoming hackathons, see the [[Hackathon]] page.<br />
<br />
== Conferences ==<br />
<br />
See the [[Haskell_in_research#Conferences|Haskell in research]] and [[Conferences]] page for academic workshops and conferences<br />
focusing on Haskell and related technology.</div>TillmannRendelhttps://wiki.haskell.org/index.php?title=GHC/Type_families&diff=36471GHC/Type families2010-08-09T11:17:06Z<p>TillmannRendel: /* Injectivity, type inference, and ambiguity */ mention data families</p>
<hr />
<div>[[Category:GHC|Indexed types]]<br />
<br />
Indexed type families, or '''type families''' for short, are a Haskell extension supporting ad-hoc overloading of data types. Type families are parametric types that can be assigned specialized representations based on the type parameters they are instantiated with. They are the data type analogue of [[Type class|type classes]]: families are used to define overloaded ''data'' in the same way that classes are used to define overloaded ''functions''. Type families are useful for generic programming, for creating highly parameterised library interfaces, and for creating interfaces with enhanced static information, much like dependent types.<br />
<br />
Type families come in two flavors: ''data families'' and ''type synonym families''. Data families are the indexed form of data and newtype definitions. Type synonym families are the indexed form of type synonyms. Each of these flavors can be defined in a standalone manner or ''associated'' with a type class. Standalone definitions are more general, while associated types can more clearly express how a type is used and lead to better error messages.<br />
<br />
== What are type families? ==<br />
<br />
The concept of a type family comes from type theory. An indexed type family in type theory is a partial function at the type level. Applying the function to parameters (called ''type indices'') yields a type. Type families permit a program to compute what data constructors it will operate on, rather than having them fixed statically (as with simple type systems) or treated as opaque unknowns (as with parametrically polymorphic types).<br />
<br />
Type families are to vanilla data types what type class methods are to regular functions. Vanilla polymorphic data types and functions have a single definition, which is used at all type instances. Classes and type families, on the other hand, have an interface definition and any number of instance definitions. A type family's interface definition declares its [[kind]] and its arity, or the number of type indices it takes. Instance definitions define the type family over some part of the domain.<br />
<br />
As a simple example of how type families differ from ordinary parametric data types, consider a strict list type. We can represent a list of <hask>Char</hask> in the usual way, with cons cells. We can do the same thing to represent a list of <hask>()</hask>, but since a strict <hask>()</hask> value carries no useful information, it would be more efficient to just store the length of the list. This can't be done with an ordinary parametric data type, because the data constructors used to represent the list would depend on the list's type parameter: if it's <hask>Char</hask> then the list consists of cons cells; if it's <hask>()</hask>, then the list consists of a single integer. We basically want to select between two different data types based on a type parameter. Using type families, this list type could be declared as follows:<br />
<br />
<haskell><br />
-- Declare a list-like data family<br />
data family XList a<br />
<br />
-- Declare a list-like instance for Char<br />
data instance XList Char = XCons !Char !(XList Char) | XNil<br />
<br />
-- Declare a number-like instance for ()<br />
data instance XList () = XListUnit !Int<br />
</haskell><br />
<br />
The right-hand sides of the two <code>data instance</code> declarations are exactly ordinary data definitions. However, they define two instances of the same parametric data type, <hask>XList Char</hask> and <hask>XList ()</hask>, whereas ordinary data declarations define completely unrelated types. A recent [[Simonpj/Talk:FunWithTypeFuns|tutorial paper]] has more in-depth examples of programming with type families. <br />
<br />
GADTs bear some similarity to type families, in the sense that they allow a parametric type's constructors to depend on the type's parameters. However, all GADT constructors must be defined in one place, whereas type families can be extended. Functional dependences are similar to type families, and many type classes that use functional dependences can be equivalently expressed with type families. Type families provide a more functional style of type-level programming than the relational style of functional dependences.<br />
<br />
== What do I need to use type families? ==<br />
<br />
Type families are a GHC extension enabled with the <code>-XTypeFamilies</code> flag or the <code>{-# LANGUAGE TypeFamilies #-}</code> pragma. The first stable release of GHC that properly supports type families is 6.10.1. (The 6.8 release included an early partial implementation, but its use is deprecated.) Please [http://hackage.haskell.org/trac/ghc/query?status=new&status=assigned&status=reopened&group=priority&type=bug&order=id&desc=1 report bugs] via the GHC bug tracker, ideally accompanied by a small example program that demonstrates the problem. Use the [mailto:glasgow-haskell-users@haskell.org GHC mailing list] for questions or for a discussion of this language extension and its description on this wiki page.<br />
<br />
== An associated data type example ==<br />
<br />
As an example, consider Ralf Hinze's [http://www.informatik.uni-bonn.de/~ralf/publications.html#J4 generalised tries], a form of generic finite maps. <br />
<br />
=== The class declaration ===<br />
<br />
We define a type class whose instances are the types that we can use as keys in our generic maps:<br />
<haskell><br />
class GMapKey k where<br />
data GMap k :: * -> *<br />
empty :: GMap k v<br />
lookup :: k -> GMap k v -> Maybe v<br />
insert :: k -> v -> GMap k v -> GMap k v<br />
</haskell><br />
The interesting part is the ''associated data family'' declaration of the class. It gives a [http://www.haskell.org/ghc/docs/latest/html/users_guide/type-families.html#data-family-declarations ''kind signature''] (here <hask>* -> *</hask>) for the associated data type <hask>GMap k</hask> - analogous to how methods receive a type signature in a class declaration.<br />
<br />
What it is important to notice is that the first parameter of the associated type <hask>GMap</hask> coincides with the class parameter of <hask>GMapKey</hask>. This indicates that also in all instances of the class, the instances of the associated data type need to have their first argument match up with the instance type. In general, the type arguments of an associated type can be a subset of the class parameters (in a multi-parameter type class) and they can appear in any order, possibly in an order other than in the class head. The latter can be useful if the associated data type is partially applied in some contexts.<br />
<br />
The second important point is that as <hask>GMap k</hask> has kind <hask>* -> *</hask> and <hask>k</hask> (implicitly) has kind <hask>*</hask>, the type constructor <hask>GMap</hask> (without an argument) has kind <hask>* -> * -> *</hask>. Consequently, we see that <hask>GMap</hask> is applied to two arguments in the signatures of the methods <hask>empty</hask>, <hask>lookup</hask>, and <hask>insert</hask>.<br />
<br />
=== An Int instance ===<br />
<br />
To use Ints as keys into generic maps, we declare an instance that simply uses <hask>Data.IntMap</hask>, thusly:<br />
<haskell><br />
instance GMapKey Int where<br />
data GMap Int v = GMapInt (Data.IntMap.IntMap v)<br />
empty = GMapInt Data.IntMap.empty<br />
lookup k (GMapInt m) = Data.IntMap.lookup k m<br />
insert k v (GMapInt m) = GMapInt (Data.IntMap.insert k v m)<br />
</haskell><br />
The <hask>Int</hask> instance of the associated data type <hask>GMap</hask> needs to have both of its parameters, but as only the first one corresponds to a class parameter, the second needs to be a type variable (here <hask>v</hask>). As mentioned before, any associated type parameter that corresponds to a class parameter must be identical to the class parameter in each instance. The right hand side of the associated data declaration is like that of any other data type.<br />
<br />
NB: At the moment, GADT syntax is not allowed for associated data types (or other indexed types). This is not a fundamental limitation, but just a shortcoming of the current implementation, which we expect to lift in the future.<br />
<br />
As an exercise, implement an instance for <hask>Char</hask> that maps back to the <hask>Int</hask> instance using the conversion functions <hask>Char.ord</hask> and <hask>Char.chr</hask>.<br />
<br />
=== A unit instance ===<br />
<br />
Generic definitions, apart from elementary types, typically cover units, products, and sums. We start here with the unit instance for <hask>GMap</hask>:<br />
<haskell><br />
instance GMapKey () where<br />
data GMap () v = GMapUnit (Maybe v)<br />
empty = GMapUnit Nothing<br />
lookup () (GMapUnit v) = v<br />
insert () v (GMapUnit _) = GMapUnit $ Just v<br />
</haskell><br />
For unit, the map is just a <hask>Maybe</hask> value.<br />
<br />
=== Product and sum instances ===<br />
<br />
Next, let us define the instances for pairs and sums (i.e., <hask>Either</hask>):<br />
<haskell><br />
instance (GMapKey a, GMapKey b) => GMapKey (a, b) where<br />
data GMap (a, b) v = GMapPair (GMap a (GMap b v))<br />
empty = GMapPair empty<br />
lookup (a, b) (GMapPair gm) = lookup a gm >>= lookup b <br />
insert (a, b) v (GMapPair gm) = GMapPair $ case lookup a gm of<br />
Nothing -> insert a (insert b v empty) gm<br />
Just gm2 -> insert a (insert b v gm2 ) gm<br />
<br />
instance (GMapKey a, GMapKey b) => GMapKey (Either a b) where<br />
data GMap (Either a b) v = GMapEither (GMap a v) (GMap b v)<br />
empty = GMapEither empty empty<br />
lookup (Left a) (GMapEither gm1 _gm2) = lookup a gm1<br />
lookup (Right b) (GMapEither _gm1 gm2 ) = lookup b gm2<br />
insert (Left a) v (GMapEither gm1 gm2) = GMapEither (insert a v gm1) gm2<br />
insert (Right b) v (GMapEither gm1 gm2) = GMapEither gm1 (insert b v gm2)<br />
</haskell><br />
If you find this code algorithmically surprising, I'd suggest to have a look at [http://www.informatik.uni-bonn.de/~ralf/publications.html#J4 Ralf Hinze's paper]. The only novelty concerning associated types, in these two instances, is that the instances have a context <hask>(GMapKey a, GMapKey b)</hask>. Consequently, the right hand sides of the associated type declarations can use <hask>GMap</hask> recursively at the key types <hask>a</hask> and <hask>b</hask> - not unlike the method definitions use the class methods recursively at the types for which the class is given in the instance context.<br />
<br />
=== Using a generic map ===<br />
<br />
Finally, some code building and querying a generic map:<br />
<haskell><br />
myGMap :: GMap (Int, Either Char ()) String<br />
myGMap = insert (5, Left 'c') "(5, Left 'c')" $<br />
insert (4, Right ()) "(4, Right ())" $<br />
insert (5, Right ()) "This is the one!" $<br />
insert (5, Right ()) "This is the two!" $<br />
insert (6, Right ()) "(6, Right ())" $<br />
insert (5, Left 'a') "(5, Left 'a')" $<br />
empty<br />
main = putStrLn $ maybe "Couldn't find key!" id $ lookup (5, Right ()) myGMap<br />
</haskell><br />
<br />
=== Download the code ===<br />
<br />
If you want to play with this example without copying it off the wiki, just download the [http://darcs.haskell.org/testsuite/tests/ghc-regress/indexed-types/should_run/GMapAssoc.hs source code for <hask>GMap</hask>] from GHC's test suite.<br />
<br />
== Detailed definition of data families ==<br />
<br />
Data families appear in two flavours: (1) they can be defined on the toplevel or (2) they can appear inside type classes (in which case they are known as associated types). The former is the more general variant, as it lacks the requirement for the type-indices to coincide with the class parameters. However, the latter can lead to more clearly structured code and compiler warnings if some type instances were - possibly accidentally - omitted. In the following, we always discuss the general toplevel form first and then cover the additional constraints placed on associated types.<br />
<br />
=== Family declarations ===<br />
<br />
Indexed data families are introduced by a signature, such as <br />
<haskell><br />
data family GMap k :: * -> *<br />
</haskell><br />
The special <hask>family</hask> distinguishes family from standard data declarations. The result kind annotation is optional and, as usual, defaults to <hask>*</hask> if omitted. An example is<br />
<haskell><br />
data family Array e<br />
</haskell><br />
Named arguments can also be given explicit kind signatures if needed. Just as with [http://www.haskell.org/ghc/docs/latest/html/users_guide/gadt.html GADT declarations] named arguments are entirely optional, so that we can declare <hask>Array</hask> alternatively with<br />
<haskell><br />
data family Array :: * -> *<br />
</haskell><br />
<br />
==== Associated family declarations ====<br />
<br />
When a data family is declared as part of a type class, we drop the <hask>family</hask> keyword. The <hask>GMap</hask> declaration takes the following form<br />
<haskell><br />
class GMapKey k where<br />
data GMap k :: * -> *<br />
...<br />
</haskell><br />
In contrast to toplevel declarations, named arguments must be used for all type parameters that are to be used as type-indices. Moreover, the argument names must be class parameters. Each class parameter may only be used at most once per associated type, but some may be omitted and they may be in an order other than in the class head. In other words: '''the named type parameters of the data declaration must be a permutation of a subset of the class variables'''. <br />
<br />
Example is admissible:<br />
<haskell><br />
class C a b c where { data T c a :: * } -- OK<br />
class C a b c where { data T a a :: * } -- Bad: repeated variable<br />
class D a where { data T a x :: * } -- Bad: x is not a class variable<br />
class D a where { data T a :: * -> * } -- OK<br />
</haskell><br />
<br />
=== Instance declarations ===<br />
<br />
Instance declarations of data and newtype families are very similar to standard data and newtype declarations. The only two differences are that the keyword <hask>data</hask> or <hask>newtype</hask> is followed by <hask>instance</hask> and that some or all of the type arguments can be non-variable types, but may not contain forall types or type synonym families. However, data families are generally allowed in type parameters, and type synonyms are allowed as long as they are fully applied and expand to a type that is itself admissible - exactly as this is required for occurrences of type synonyms in class instance parameters. For example, the <hask>Either</hask> instance for <hask>GMap</hask> is<br />
<haskell><br />
data instance GMap (Either a b) v = GMapEither (GMap a v) (GMap b v)<br />
</haskell><br />
In this example, the declaration has only one variant. In general, it can be any number.<br />
<br />
Data and newtype instance declarations are only legit when an appropriate family declaration is in scope - just like class instances require the class declaration to be visible. Moreover, each instance declaration has to conform to the kind determined by its family declaration. This implies that the number of parameters of an instance declaration matches the arity determined by the kind of the family. Although all data families are declared with the <hask>data</hask> keyword, instances can be either <hask>data</hask> or <hask>newtype</hask>s, or a mix of both.<br />
<br />
Even if type families are defined as toplevel declarations, functions that perform different computations for different family instances still need to be defined as methods of type classes. In particular, the following is not possible:<br />
<haskell><br />
data family T a<br />
data instance T Int = A<br />
data instance T Char = B<br />
nonsense :: T a -> Int<br />
nonsense A = 1 -- WRONG: These two equations together...<br />
nonsense B = 2 -- ...will produce a type error.<br />
</haskell><br />
Given the functionality provided by GADTs (Generalised Algebraic Data Types), it might seem as if a definition, such as the above, should be feasible. However, type families - in contrast to GADTs - are ''open''; i.e., new instances can always be added, possibly in other modules. Supporting pattern matching across different data instances would require a form of extensible case construct.<br />
<br />
==== Associated type instances ====<br />
<br />
When an associated family instance is declared within a type class instance, we drop the <hask>instance</hask> keyword in the family instance. So, the <hask>Either</hask> instance for <hask>GMap</hask> becomes:<br />
<haskell><br />
instance (GMapKey a, GMapKey b) => GMapKey (Either a b) where<br />
data GMap (Either a b) v = GMapEither (GMap a v) (GMap b v<br />
...<br />
</haskell><br />
The most important point about associated family instances is that the type indices corresponding to class parameters must be identical to the type given in the instance head; here this is the first argument of <hask>GMap</hask>, namely <hask>Either a b</hask>, which coincides with the only class parameter. Any parameters to the family constructor that do not correspond to class parameters, need to be variables in every instance; here this is the variable <hask>v</hask>.<br />
<br />
Instances for an associated family can only appear as part of instance declarations of the class in which the family was declared - just as with the equations of the methods of a class. Also in correspondence to how methods are handled, declarations of associated types can be omitted in class instances. If an associated family instance is omitted, the corresponding instance type is not inhabited; i.e., only diverging expressions, such as <hask>undefined</hask>, can assume the type.<br />
<br />
==== Scoping of class parameters ====<br />
<br />
In the case of multi-parameter type classes, the visibility of class parameters in the right-hand side of associated family instances depends ''solely'' on the parameters of the data family. As an example, consider the simple class declaration<br />
<haskell><br />
class C a b where<br />
data T a<br />
</haskell><br />
Only one of the two class parameters is a parameter to the data family. Hence, the following instance declaration is invalid:<br />
<haskell><br />
instance C [c] d where<br />
data T [c] = MkT (c, d) -- WRONG!! 'd' is not in scope<br />
</haskell><br />
Here, the right-hand side of the data instance mentions the type variable <hask>d</hask> that does not occur in its left-hand side. We cannot admit such data instances as they would compromise type safety.<br />
<br />
==== Type class instances of family instances ====<br />
<br />
Type class instances of instances of data families can be defined as usual, and in particular data instance declarations can have <hask>deriving</hask> clauses. For example, we can write<br />
<haskell><br />
data GMap () v = GMapUnit (Maybe v)<br />
deriving Show<br />
</haskell><br />
which implicitly defines an instance of the form<br />
<haskell><br />
instance Show v => Show (GMap () v) where ...<br />
</haskell><br />
<br />
Note that class instances are always for particular ''instances'' of a data family and never for an entire family as a whole. This is for essentially the same reasons that we cannot define a toplevel function that performs pattern matching on the data constructors of ''different'' instances of a single type family. It would require a form of extensible case construct.<br />
<br />
==== Overlap ====<br />
<br />
The instance declarations of a data family used in a single program may not overlap at all, independent of whether they are associated or not. In contrast to type class instances, this is not only a matter of consistency, but one of type safety.<br />
<br />
=== Import and export ===<br />
<br />
The association of data constructors with type families is more dynamic than that is the case with standard data and newtype declarations. In the standard case, the notation <hask>T(..)</hask> in an import or export list denotes the type constructor and all the data constructors introduced in its declaration. However, a family declaration never introduces any data constructors; instead, data constructors are introduced by family instances. As a result, which data constructors are associated with a type family depends on the currently visible instance declarations for that family. Consequently, an import or export item of the form <hask>T(..)</hask> denotes the family constructor and all currently visible data constructors - in the case of an export item, these may be either imported or defined in the current module. The treatment of import and export items that explicitly list data constructors, such as <hask>GMap(GMapEither)</hask>, is analogous.<br />
<br />
==== Associated families ====<br />
<br />
As expected, an import or export item of the form <hask>C(..)</hask> denotes all of the class' methods and associated types. However, when associated types are explicitly listed as subitems of a class, we need some new syntax, as uppercase identifiers as subitems are usually data constructors, not type constructors. To clarify that we denote types here, each associated type name needs to be prefixed by the keyword <hask>type</hask>. So for example, when explicitly listing the components of the <hask>GMapKey</hask> class, we write <hask>GMapKey(type GMap, empty, lookup, insert)</hask>.<br />
<br />
==== Examples ====<br />
<br />
Assuming our running <hask>GMapKey</hask> class example, let us look at some export lists and their meaning:<br />
<br />
* <hask>module GMap (GMapKey) where...</hask>: Exports just the class name.<br />
* <hask>module GMap (GMapKey(..)) where...</hask>: Exports the class, the associated type <hask>GMap</hask> and the member functions <hask>empty</hask>, <hask>lookup</hask>, and <hask>insert</hask>. None of the data constructors is exported.<br />
* <hask>module GMap (GMapKey(..), GMap(..)) where...</hask>: As before, but also exports all the data constructors <hask>GMapInt</hask>, <hask>GMapChar</hask>, <hask>GMapUnit</hask>, <hask>GMapPair</hask>, and <hask>GMapEither</hask>.<br />
* <hask>module GMap (GMapKey(empty, lookup, insert), GMap(..)) where...</hask>: As before.<br />
* <hask>module GMap (GMapKey, empty, lookup, insert, GMap(..)) where...</hask>: As before.<br />
<br />
Finally, you can write <hask>GMapKey(type GMap)</hask> to denote both the class <hask>GMapKey</hask> as well as its associated type <hask>GMap</hask>. However, you cannot write <hask>GMapKey(type GMap(..))</hask> &mdash; i.e., sub-component specifications cannot be nested. To specify <hask>GMap</hask>'s data constructors, you have to list it separately.<br />
<br />
==== Instances ====<br />
<br />
Family instances are implicitly exported, just like class instances. However, this applies only to the heads of instances, not to the data constructors an instance defines.<br />
<br />
== An associated type synonym example ==<br />
<br />
Type synonym families are an alternative to functional dependencies, which makes functional dependency examples well suited to introduce type synonym families. In fact, type families are a more functional way to express the same as functional dependencies (despite the name!), as they replace the relational notation of functional dependencies by an expression-oriented notation; i.e., functions on types are really represented by functions and not relations.<br />
<br />
=== The <hask>class</hask> declaration ===<br />
<br />
Here's an example from Mark Jones' seminal paper on functional dependencies:<br />
<haskell><br />
class Collects e ce | ce -> e where<br />
empty :: ce<br />
insert :: e -> ce -> ce<br />
member :: e -> ce -> Bool<br />
toList :: ce -> [e]<br />
</haskell><br />
<br />
With associated type synonyms we can write this as<br />
<haskell><br />
class Collects ce where<br />
type Elem ce<br />
empty :: ce<br />
insert :: Elem ce -> ce -> ce<br />
member :: Elem ce -> ce -> Bool<br />
toList :: ce -> [Elem ce]<br />
</haskell><br />
Instead of the multi-parameter type class, we use a single parameter class, and the parameter <hask>e</hask><br />
turned into an associated type synonym <hask>Elem ce</hask>.<br />
<br />
=== An <hask>instance</hask>===<br />
<br />
Instances change correspondingly. An instance of the two-parameter class<br />
<haskell><br />
instance Eq e => Collects e [e] where<br />
empty = []<br />
insert e l = (e:l)<br />
member e [] = False<br />
member e (x:xs) <br />
| e == x = True<br />
| otherwise = member e xs<br />
toList l = l<br />
</haskell><br />
becomes an instance of a single-parameter class, where the dependent type parameter turns into an associated type instance declaration:<br />
<haskell><br />
instance Eq e => Collects [e] where<br />
type Elem [e] = e<br />
empty = []<br />
insert e l = (e:l)<br />
member e [] = False<br />
member e (x:xs) <br />
| e == x = True<br />
| otherwise = member e xs<br />
toList l = l<br />
</haskell><br />
<br />
=== Using generic collections ===<br />
<br />
With Functional Dependencies the code would be:<br />
<haskell><br />
sumCollects :: (Collects e c1, Collects e c2) => c1 -> c2 -> c2<br />
sumCollects c1 c2 = foldr insert c2 (toList c1)<br />
</haskell><br />
<br />
In contrast, with associated type synonyms, we get:<br />
<haskell><br />
sumCollects :: (Collects c1, Collects c2, Elem c1 ~ Elem c2) => c1 -> c2 -> c2<br />
sumCollects c1 c2 = foldr insert c2 (toList c1)<br />
</haskell><br />
<br />
== Detailed definition of type synonym families ==<br />
<br />
Type families appear in two flavours: (1) they can be defined on the toplevel or (2) they can appear inside type classes (in which case they are known as associated type synonyms). The former is the more general variant, as it lacks the requirement for the type-indices to coincide with the class parameters. However, the latter can lead to more clearly structured code and compiler warnings if some type instances were - possibly accidentally - omitted. In the following, we always discuss the general toplevel form first and then cover the additional constraints placed on associated types.<br />
<br />
=== Family declarations ===<br />
<br />
Indexed type families are introduced by a signature, such as <br />
<haskell><br />
type family Elem c :: *<br />
</haskell><br />
The special <hask>family</hask> distinguishes family from standard type declarations. The result kind annotation is optional and, as usual, defaults to <hask>*</hask> if omitted. An example is<br />
<haskell><br />
type family Elem c<br />
</haskell><br />
Parameters can also be given explicit kind signatures if needed. We call the number of parameters in a type family declaration, the family's arity, and all applications of a type family must be fully saturated w.r.t. to that arity. This requirement is unlike ordinary type synonyms and it implies that the kind of a type family is not sufficient to determine a family's arity, and hence in general, also insufficient to determine whether a type family application is well formed. As an example, consider the following declaration:<br />
<haskell><br />
type family F a b :: * -> * -- F's arity is 2, <br />
-- although its overall kind is * -> * -> * -> *<br />
</haskell><br />
Given this declaration the following are examples of well-formed and malformed types:<br />
<haskell><br />
F Char [Int] -- OK! Kind: * -> *<br />
F Char [Int] Bool -- OK! Kind: *<br />
F IO Bool -- WRONG: kind mismatch in the first argument<br />
F Bool -- WRONG: unsaturated application<br />
</haskell><br />
<br />
==== Associated family declarations ====<br />
<br />
When a type family is declared as part of a type class, we drop the <hask>family</hask> special. The <hask>Elem</hask> declaration takes the following form<br />
<haskell><br />
class Collects ce where<br />
type Elem ce :: *<br />
...<br />
</haskell><br />
Exactly as in the case of an associated data declaration, '''the named type parameters must be a permutation of a subset of the class parameters'''. Examples<br />
<haskell><br />
class C a b c where { type T c a :: * } -- OK<br />
class D a where { type T a x :: * } -- No: x is not a class parameter<br />
class D a where { type T a :: * -> * } -- OK<br />
</haskell><br />
<br />
=== Instance declarations ===<br />
<br />
Instance declarations of type families are very similar to standard type synonym declarations. The only two differences are that the keyword <hask>type</hask> is followed by <hask>instance</hask> and that some or all of the type arguments can be non-variable types, but may not contain forall types or type synonym families. However, data families are generally allowed, and type synonyms are allowed as long as they are fully applied and expand to a type that is admissible - these are the exact same requirements as for data instances. For example, the <hask>[e]</hask> instance for <hask>Elem</hask> is<br />
<haskell><br />
type instance Elem [e] = e<br />
</haskell><br />
<br />
A type family instance declaration must satisfy the following rules:<br />
* An appropriate family declaration is in scope - just like class instances require the class declaration to be visible. <br />
* The instance declaration conforms to the kind determined by its family declaration<br />
* The number of type parameters in an instance declaration matches the number of type parameters in the family declaration.<br />
* The right-hand side of a type instance must be a monotype (i.e., it may not include foralls) and after the expansion of all saturated vanilla type synonyms, no synonyms, except family synonyms may remain.<br />
<br />
Here are some examples of admissible and illegal type instances:<br />
<haskell><br />
type family F a :: *<br />
type instance F [Int] = Int -- OK!<br />
type instance F String = Char -- OK!<br />
type instance F (F a) = a -- WRONG: type parameter mentions a type family<br />
type instance F (forall a. (a, b)) = b -- WRONG: a forall type appears in a type parameter<br />
type instance F Float = forall a.a -- WRONG: right-hand side may not be a forall type<br />
<br />
type family G a b :: * -> *<br />
type instance G Int = (,) -- WRONG: must be two type parameters<br />
type instance G Int Char Float = Double -- WRONG: must be two type parameters<br />
</haskell><br />
<br />
==== Associated type instances ====<br />
<br />
When an associated family instance is declared within a type class instance, we drop the <hask>instance</hask> keyword in the family instance. So, the <hask>[e]</hask> instance for <hask>Elem</hask> becomes:<br />
<haskell><br />
instance (Eq (Elem [e])) => Collects ([e]) where<br />
type Elem [e] = e<br />
...<br />
</haskell><br />
The most important point about associated family instances is that the type indexes corresponding to class parameters must be identical to the type given in the instance head; here this is <hask>[e]</hask>, which coincides with the only class parameter.<br />
<br />
Instances for an associated family can only appear as part of instance declarations of the class in which the family was declared - just as with the equations of the methods of a class. Also in correspondence to how methods are handled, declarations of associated types can be omitted in class instances. If an associated family instance is omitted, the corresponding instance type is not inhabited; i.e., only diverging expressions, such as <hask>undefined</hask>, can assume the type.<br />
<br />
==== Overlap ====<br />
<br />
The instance declarations of a type family used in a single program may only overlap if the right-hand sides of the overlapping instances coincide for the overlapping types. More formally, two instance declarations overlap if there is a substitution that makes the left-hand sides of the instances syntactically the same. Whenever that is the case, the right-hand sides of the instances must also be syntactically equal under the same substitution. This condition is independent of whether the type family is associated or not, and it is not only a matter of consistency, but one of type safety.<br />
<br />
Here are two examples to illustrate the condition under which overlap is permitted.<br />
<haskell><br />
type instance F (a, Int) = [a]<br />
type instance F (Int, b) = [b] -- overlap permitted<br />
<br />
type instance G (a, Int) = [a]<br />
type instance G (Char, a) = [a] -- ILLEGAL overlap, as [Char] /= [Int]<br />
</haskell><br />
<br />
==== Decidability ====<br />
<br />
In order to guarantee that type inference in the presence of type families is decidable, we need to place a number of additional restrictions on the formation of type instance declarations (c.f., Definition 5 (Relaxed Conditions) of [http://www.cse.unsw.edu.au/~chak/papers/SPCS08.html Type Checking with Open Type Functions]). Instance declarations have the general form<br />
<haskell><br />
type instance F t1 .. tn = t<br />
</haskell><br />
where we require that for every type family application <hask>(G s1 .. sm)</hask> in <hask>t</hask>, <br />
# <hask>s1 .. sm</hask> do not contain any type family constructors,<br />
# the total number of symbols (data type constructors and type variables) in <hask>s1 .. sm</hask> is strictly smaller than in <hask>t1 .. tn</hask>, and<br />
# for every type variable <hask>a</hask>, <hask>a</hask> occurs in <hask>s1 .. sm</hask> at most as often as in <hask>t1 .. tn</hask>.<br />
These restrictions are easily verified and ensure termination of type inference. However, they are not sufficient to guarantee completeness of type inference in the presence of, so called, ''loopy equalities'', such as <hask>a ~ [F a]</hask>, where a recursive occurrence of a type variable is underneath a family application and data constructor application - see the above mentioned paper for details. <br />
<br />
If the option <tt>-XUndecidableInstances</tt> is passed to the compiler, the above restrictions are not enforced and it is on the programmer to ensure termination of the normalisation of type families during type inference.<br />
<br />
=== Equality constraints ===<br />
<br />
Type context can include equality constraints of the form <hask>t1 ~ t2</hask>, which denote that the types <hask>t1</hask> and <hask>t2</hask> need to be the same. In the presence of type families, whether two types are equal cannot generally be decided locally. Hence, the contexts of function signatures may include equality constraints, as in the following example:<br />
<haskell><br />
sumCollects :: (Collects c1, Collects c2, Elem c1 ~ Elem c2) => c1 -> c2 -> c2<br />
</haskell><br />
where we require that the element type of <hask>c1</hask> and <hask>c2</hask> are the same. In general, the types <hask>t1</hask> and <hask>t2</hask> of an equality constraint may be arbitrary monotypes; i.e., they may not contain any quantifiers, independent of whether higher-rank types are otherwise enabled.<br />
<br />
Equality constraints can also appear in class and instance contexts. The former enable a simple translation of programs using functional dependencies into programs using family synonyms instead. The general idea is to rewrite a class declaration of the form<br />
<haskell><br />
class C a b | a -> b<br />
</haskell><br />
to<br />
<haskell><br />
class (F a ~ b) => C a b where<br />
type F a<br />
</haskell><br />
That is, we represent every functional dependency (FD) <hask>a1 .. an -> b</hask> by an FD type family <hask>F a1 .. an</hask> and a superclass context equality <hask>F a1 .. an ~ b</hask>, essentially giving a name to the functional dependency. In class instances, we define the type instances of FD families in accordance with the class head. Method signatures are not affected by that process.<br />
<br />
NB: Equalities in superclass contexts are not fully implemented in the GHC 6.10 branch.<br />
<br />
== Frequently asked questions ==<br />
<br />
=== Injectivity, type inference, and ambiguity ===<br />
<br />
A common problem is this<br />
<haskell><br />
type family F a<br />
<br />
f :: F a -> F a<br />
f = undefined<br />
<br />
g :: F Int -> F Int<br />
g x = f x<br />
</haskell><br />
The compiler complains about the definition of <tt>g</tt> saying<br />
<haskell><br />
Couldn't match expected type `F Int' against inferred type `F a1'<br />
</haskell><br />
In type-checking <tt>g</tt>'s right hand side GHC discovers (by instantiating <tt>f</tt>'s type with a fresh type variable) that it has type <tt>F a1 -> F a1</tt> for some as-yet-unknown type <tt>a1</tt>. Now it tries to make the inferred type match <tt>g</tt>'s type signature. Well, you say, just make <tt>a1</tt> equal to <tt>Int</tt> and you are done. True, but what if there were these instances<br />
<haskell><br />
type instance F Int = Bool<br />
type instance F Char = Bool<br />
</haskell><br />
Then making <tt>a1</tt> equal to <tt>Char</tt> would ''also'' make the two types equal. Because there is more than one choice, the program is rejected.<br />
<br />
Or, to put it another way, knowing that <tt>F t1</tt>=<tt>F t2</tt> does ''not'' imply that <tt>t1</tt> = <tt>t2</tt>.<br />
The difficulty is that the type function <tt>F</tt> need not be ''injective''; it can map two distinct types to the same type. For an injective type constructor like <tt>Maybe</tt>, if we know that <tt>Maybe t1</tt> = <tt>Maybe t2</tt>, then we know that <tt>t1</tt> = <tt>t2</tt>. But not so for non-injective type functions.<br />
<br />
The problem starts with <tt>f</tt>. Its type is ''ambiguous''; even if I know the argument and result types for <tt>f</tt>, I cannot use that to find the type at which <tt>a</tt> should be instantiated. (So arguably, <tt>f</tt> should be rejected as having an ambiguous type, and probably will be in future.) The situation is well known in type classes: <br />
<haskell><br />
bad :: (Read a, Show a) => String -> String<br />
bad x = show (read x)<br />
</haskell><br />
At a call of <tt>bad</tt> one cannot tell at what type <tt>a</tt> should be instantiated.<br />
<br />
The only solution is to avoid ambiguous types. In the type signature of a function, <br />
* Ensure that every type variable occurs in the part after the "<tt>=></tt>"<br />
* Ensure that every type variable appears at least once outside a type function call. <br />
<br />
Even then ambiguity is possible. For example:<br />
<haskell><br />
f :: F a -> [a] <br />
f = undefined<br />
<br />
g :: F b -> Int<br />
g x = length (f x)<br />
</haskell><br />
Although <tt>f</tt>'s type is unambiguous, its result type is swallowed up by <tt>length</tt>, which now makes <tt>g</tt>'s type ambiguous.<br />
<br />
Above ambiguity is caused by <tt>F</tt> being a type family, so it is possibly non-injective. However, data families are always injective, so the following code works:<br />
<br />
<haskell>data family F a<br />
<br />
f :: F a -> F a<br />
f = undefined<br />
<br />
g :: F Int -> F Int<br />
g x = f x</haskell><br />
<br />
== References ==<br />
<br />
* [http://www.cse.unsw.edu.au/~chak/papers/CKPM05.html Associated Types with Class.] Manuel M. T. Chakravarty, Gabriele Keller, Simon Peyton Jones, and Simon Marlow. In ''Proceedings of The 32nd Annual ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages (POPL'05)'', pages 1-13, ACM Press, 2005.<br />
* [http://www.cse.unsw.edu.au/~chak/papers/CKP05.html Associated Type Synonyms.] Manuel M. T. Chakravarty, Gabriele Keller, and Simon Peyton Jones. In ''Proceedings of The Tenth ACM SIGPLAN International Conference on Functional Programming'', ACM Press, pages 241-253, 2005.<br />
* [http://www.cse.unsw.edu.au/~chak/papers/SCPD07.html System F with Type Equality Coercions.] Martin Sulzmann, Manuel M. T. Chakravarty, Simon Peyton Jones, and Kevin Donnelly. In ''Proceedings of The Third ACM SIGPLAN Workshop on Types in Language Design and Implementation'', ACM Press, 2007.<br />
* [http://www.cse.unsw.edu.au/~chak/papers/SPCS08.html Type Checking With Open Type Functions.] Tom Schrijvers, Simon Peyton-Jones, Manuel M. T. Chakravarty, Martin Sulzmann. In ''Proceedings of The 13th ACM SIGPLAN International Conference on Functional Programming'', ACM Press, pages 51-62, 2008.<br />
<br />
[[Category:Type-level programming]]<br />
[[Category:Language extension]]</div>TillmannRendelhttps://wiki.haskell.org/index.php?title=ICFP_Programming_Contest/Teams_2007&diff=14211ICFP Programming Contest/Teams 20072007-07-11T21:10:57Z<p>TillmannRendel: removed myself from the list of team searching people</p>
<hr />
<div>This page is for helping Haskell (and FP) people organise teams for the<br />
[http://www.icfpcontest.org// 2007 ICFP contest].<br />
<br />
* [http://www.kingsrook.com/icfp/countdown.html Countdown to contest start]<br />
<br />
Resources:<br />
* The home of [http://www.icfpcontest.org/ ICFP 2007].<br />
* The #haskell-icfp07 and #haskell [[IRC channel]]s on freenode.<br />
* [http://article.gmane.org/gmane.comp.lang.haskell.cafe/24773 Announcement] for this page.<br />
<br />
== Teams ==<br />
<br />
Teams that are completed, and will be entering:<br />
<br />
{| border="0" cellspacing="0" cellpadding="2"<br />
! Team<br />
! Members<br />
|-<br />
| Lazy Bottoms<br />
| vincenz, Adept, Lemmih, psykotic, zeeeeee, jethr0, Cale<br />
|}<br />
<br />
== Teams seeking players ==<br />
<br />
Are you organising a team, and need more players? Add your team and<br />
contact details here:<br />
<br />
{| border="0" cellspacing="0" cellpadding="2"<br />
! Team<br />
! Current members<br />
! Number required<br />
! Contact<br />
|-<br />
| ''CoolHackers''<br />
| ''0''<br />
| ''0''<br />
| ''lambdabot @ #haskell''<br />
|-<br />
| FieryNewbz<br />
| 3<br />
| 5<br />
| syntaxfree @ #haskell<br />
|-<br />
| TNT <team named thunk><br />
| 3<br />
| 5<br />
| timbod @ #haskell, twd_gg AT dockerz DOT net<br />
|}<br />
<br />
== Interested in competing ==<br />
<br />
Interested in competing, but need a team? Add your name and how to<br />
contact you here, and '''start contacting people on #haskell, and this<br />
list, to organise your team!'''<br />
<br />
{| border="0"<br />
! Name<br />
! Location<br />
! Skills<br />
! Contact<br />
|-<br />
| ''Lambdabot''<br />
| ''Sydney''<br />
| ''Looking up documentation''<br />
| ''#haskell''<br />
|-<br />
| jfredett (Joe Fredette)<br />
| Bellingham, MA, US of A<br />
| Math, Math, and more Math, Scheme too.<br />
| AIM: Joeyfredette / #haskell<br />
|-<br />
| ilyats<br />
| Israel<br />
| Math, Haskell98<br />
| eilya497 at 013.net<br />
|-<br />
| Andrew Wagner<br />
| US (EST time zone)<br />
| Math modelling, AI<br />
| chessguy on #haskell or wagner dot andrew _at_ gmail<br />
|-<br />
| Tim Chevalier <br />
| Portland, OR<br />
| Um... besides Haskell?<br />
| catamorphism@gmail.com / catamorphism on AIM / Binkley on #haskell<br />
|-<br />
| Tim Docker<br />
| Sydney<br />
| graphics, visualisation, distributed processing<br />
| timbod on #haskell (sporadically), or twd_gg AT dockerz DOT net<br />
|-<br />
| Arthur van Leeuwen<br />
| Utrecht, The Netherlands<br />
| parsing, language design<br />
| earthy on #haskell, #haskell.dut<br />
|-<br />
| Diego Navarro<br />
| Brazil<br />
| random bits of formal logic, statistics (LOTS of it, graduate-level), some random knowledge of Bird-Merteens Formalism. Oh, and economics, I'm actually an economist<br />
| quemseatreve at gmail dot com, syntaxfree on #haskell (most often on #haskell-blah, ab_gen@hotmail.com on MSN <br />
|-<br />
| Ivan Tarasov<br />
| St.Petersburg, Russia<br />
| Math, Haskell, some D, Ruby, some boring languages (Java, C, C++)<br />
| Ivan.Tarasov at gmail com, ivant on #haskell (sporadically), JabberID: tarasov@jabber.ru<br />
|}<br />
<br />
== How to contact people ==<br />
<br />
If possible, mention your nick on #haskell @ freenode.org, or #haskell-icfp07 @ freenode.org, then you'll be much easier to find.<br />
<br />
[[Category:Contest]]</div>TillmannRendelhttps://wiki.haskell.org/index.php?title=ICFP_Programming_Contest/Teams_2007&diff=13996ICFP Programming Contest/Teams 20072007-07-04T15:34:31Z<p>TillmannRendel: added my irc nick</p>
<hr />
<div>This page is for helping Haskell (and FP) people organise teams for the<br />
[http://www.icfpcontest.org// 2007 ICFP contest].<br />
<br />
* [http://www.kingsrook.com/icfp/countdown.html Countdown to contest start]<br />
<br />
Resources:<br />
* The home of [http://www.icfpcontest.org/ ICFP 2007].<br />
* The #haskell-icfp07 and #haskell [[IRC channel]]s on freenode.<br />
* [http://article.gmane.org/gmane.comp.lang.haskell.cafe/24773 Announcement] for this page.<br />
<br />
== Full teams ==<br />
<br />
Teams that are completed, and will be entering:<br />
<br />
{| border="0" cellspacing="0" cellpadding="2"<br />
! Team<br />
! Members<br />
|-<br />
|}<br />
<br />
<br />
== Teams seeking players ==<br />
<br />
Are you organising a team, and need more players? Add your team and<br />
contact details here:<br />
<br />
{| border="0" cellspacing="0" cellpadding="2"<br />
! Team<br />
! Current members<br />
! Number required<br />
! Contact<br />
|-<br />
| ''CoolHackers''<br />
| ''0''<br />
| ''0''<br />
| ''lambdabot @ #haskell''<br />
|}<br />
<br />
== Interested in competing ==<br />
<br />
Interested in competing, but need a team? Add your name and how to<br />
contact you here:<br />
<br />
{| border="0"<br />
! Name<br />
! Location<br />
! Skills<br />
! Contact<br />
|-<br />
| ''Lambdabot''<br />
| ''Sydney''<br />
| ''Looking up documentation''<br />
| ''#haskell''<br />
|-<br />
| jfredett (Joe Fredette)<br />
| Bellingham, MA, US of A<br />
| Math, Math, and more Math, Scheme too.<br />
| AIM: Joeyfredette / #haskell<br />
|-<br />
| mnislaih<br />
| Spain<br />
| none. sleeps less than most peeps<br />
| mnislaih@gmail.com / #haskell<br />
|-<br />
| ilyats<br />
| Israel<br />
| Math, Haskell98<br />
| eilya497 at 013.net<br />
|-<br />
| Andrew Wagner<br />
| US (EST time zone)<br />
| Math modelling, AI<br />
| chessguy on #haskell or wagner dot andrew _at_ gmail<br />
|-<br />
| desp (Mietek Bąk)<br />
| Poland<br />
| Not afraid of dirty C/C++ work<br />
| mietek@gmail.com / #haskell<br />
|-<br />
| Tim Chevalier <br />
| Portland, OR<br />
| Um... besides Haskell?<br />
| catamorphism@gmail.com / catamorphism on AIM / Binkley on #haskell<br />
|-<br />
| Tim Docker<br />
| Sydney<br />
| distributed processing<br />
| timbod on #haskell (sporadically), or twd_gg AT dockerz DOT net<br />
|-<br />
| Tillmann Rendel<br />
| Germany<br />
| programming, logic<br />
| rendel at rbg dot informatik dot tu-darmstadt dot de, Toxaris on #haskell<br />
|}<br />
<br />
== How to contact people ==<br />
<br />
If possible, mention your nick on #haskell @ freenode.org, or #haskell-icfp07 @ freenode.org, then you'll be much easier to find.<br />
<br />
[[Category:Contest]]</div>TillmannRendelhttps://wiki.haskell.org/index.php?title=ICFP_Programming_Contest/Teams_2007&diff=13994ICFP Programming Contest/Teams 20072007-07-04T14:33:11Z<p>TillmannRendel: added myself to the list</p>
<hr />
<div>This page is for helping Haskell (and FP) people organise teams for the<br />
[http://www.icfpcontest.org// 2007 ICFP contest].<br />
<br />
* [http://www.kingsrook.com/icfp/countdown.html Countdown to contest start]<br />
<br />
Resources:<br />
* The home of [http://www.icfpcontest.org/ ICFP 2007].<br />
* The #haskell-icfp07 and #haskell [[IRC channel]]s on freenode.<br />
* [http://article.gmane.org/gmane.comp.lang.haskell.cafe/24773 Announcement] for this page.<br />
<br />
== Full teams ==<br />
<br />
Teams that are completed, and will be entering:<br />
<br />
{| border="0" cellspacing="0" cellpadding="2"<br />
! Team<br />
! Members<br />
|-<br />
|}<br />
<br />
<br />
== Teams seeking players ==<br />
<br />
Are you organising a team, and need more players? Add your team and<br />
contact details here:<br />
<br />
{| border="0" cellspacing="0" cellpadding="2"<br />
! Team<br />
! Current members<br />
! Number required<br />
! Contact<br />
|-<br />
| ''CoolHackers''<br />
| ''0''<br />
| ''0''<br />
| ''lambdabot @ #haskell''<br />
|}<br />
<br />
== Interested in competing ==<br />
<br />
Interested in competing, but need a team? Add your name and how to<br />
contact you here:<br />
<br />
{| border="0"<br />
! Name<br />
! Location<br />
! Skills<br />
! Contact<br />
|-<br />
| ''Lambdabot''<br />
| ''Sydney''<br />
| ''Looking up documentation''<br />
| ''#haskell''<br />
|-<br />
| jfredett (Joe Fredette)<br />
| Bellingham, MA, US of A<br />
| Math, Math, and more Math, Scheme too.<br />
| AIM: Joeyfredette / #haskell<br />
|-<br />
| mnislaih<br />
| Spain<br />
| none. sleeps less than most peeps<br />
| mnislaih@gmail.com / #haskell<br />
|-<br />
| ilyats<br />
| Israel<br />
| Math, Haskell98<br />
| eilya497 at 013.net<br />
|-<br />
| Andrew Wagner<br />
| US (EST time zone)<br />
| Math modelling, AI<br />
| chessguy on #haskell or wagner dot andrew _at_ gmail<br />
|-<br />
| desp (Mietek Bąk)<br />
| Poland<br />
| Not afraid of dirty C/C++ work<br />
| mietek@gmail.com / #haskell<br />
|-<br />
| Tim Chevalier <br />
| Portland, OR<br />
| Um... besides Haskell?<br />
| catamorphism@gmail.com / catamorphism on AIM / Binkley on #haskell<br />
|-<br />
| Tim Docker<br />
| Sydney<br />
| distributed processing<br />
| timbod on #haskell (sporadically), or twd_gg AT dockerz DOT net<br />
|-<br />
| Tillmann Rendel<br />
| Germany<br />
| programming, logic<br />
| rendel at rbg dot informatik dot tu-darmstadt dot de<br />
|}<br />
<br />
== How to contact people ==<br />
<br />
If possible, mention your nick on #haskell @ freenode.org, or #haskell-icfp07 @ freenode.org, then you'll be much easier to find.<br />
<br />
[[Category:Contest]]</div>TillmannRendel