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Text of the page (random words):
haskell language get started downloads playground community documentation security donate blog enjoy long term maintainable software you can rely on declarative statically typed code primes filterprime 2 where filterprime p xs p filterprime x x xs x mod p 0 get started try it try haskell requires javascript to be enabled try haskell requires cookies to be enabled why haskell a new paradigm express your ideas clearly and learn a new way of thinking about programming based on lambda calculus haskell is a purely functional programming language that features referential transparency immutability and lazy evaluation concepts that will blow your mind relearn programming while having an absolute blast composition and predictability reason about large pieces of code and compose them easily there is no global state or mutable variables obscuring the meaning of your program the strong type system makes sure there are no surprises never again will you have to guess what your program does at execution time declarative write your programs declaratively by utilizing the power of pure functions and algebraic data types in haskell we don t write how a program should be executed we just describe its logic never again be forced to think about evaluation order or execution details performance squeeze out the last ticks of your multi core processors thanks to best in class support for async concurrent and parallel programming made possible via garbage collection and green threads use advanced streaming libraries for ultra efficient data processing abstraction build powerful abstractions that are not possible in other languages only your imagination is the limit due to polymorphism type classes and more advanced typesystem features haskell has its roots in programming language research and will always be at the forefront of expressivity excellent tooling a tooling story that s truly amazing spawn your toolchain with ghcup build your project with cabal get editor integration with haskell language server everything at your fingertips ghc is the next generation compiler that supports all of your favorite platforms videos escape from the ivory tower the haskell journey by simon peyton jones functional programming haskell by computerphile john hughes past and present of haskell interview with simon peyton jones functional programming in haskell by graham hutton what is a monad by computerphile graham hutton the haskell unfolder dijkstra s shortest paths by andres löh and edsko de vries testimonials bellroy we ve found the stability maintainability and performance of haskell to be exceptional and we look forward to more of that in the years to come bitnomial haskell gives us huge leverage over our complex business domain while allowing us to stay nimble and innovate the type system allows us to integrate new knowledge quickly and refactor our sizeable code base with relative ease calabrio at calabrio we use haskell to build our customer intelligence and analytics platform calabrio advanced reporting haskell s robust typing and semantics offer us important guarantees for our data operations and processes centralapp we use haskell because solving complex problems well requires the best tools in the business e bot7 haskell allows us to create powerful reliable software with confidence it allows us to detect unwanted behavior before it shows up in our production environment finn no finn no is an online classified ad site and we use haskell in production it allows us to express business logic with focus on correctness and we benefit greatly from the safe and joyful refactoring haskell brings fission haskell enables fission to build rock solid maintainable and performant services and tools foxhound systems at foxhound systems we build custom software for a variety of clients haskell is our first choice for building production systems because it is unrivaled in the combination of developer productivity maintainability reliability and performance that it offers hasura haskell is an ideal prototyping tool when we want to build an mvp and get a prototype out as quickly as possible haskell lets us be precise when we need to be and fast when we want to be hubspot haskell drives our data synchronization engine delivering highly configurable two way sync to our customers it enables us to build and evolve complex software with confidence at hubspot scale imagine ai imagineai is a smart code generator written in haskell that instantly turns your app spec into clean django and node source code iohk smart contract systems are largely about programming languages and when it comes to programming languages work there is no competitor to haskell mercury mercury offers banking for startups at any size or stage we use haskell to meet our customers high standards for correctness and security noredink the highest traffic features of noredink com are now served via haskell we ve seen a huge performance improvement compared to what was previously doing that work as well as a massive reduction in production error rates scarf haskell powers scarf s backend helping us move fast and not break things it offers unparalleled maintainability so we can quickly and safely adapt our system to the moving target of customer demands scrive scrive uses haskell to build secure and scalable e signing programmable document workflows and customer onboarding solutions the haskell language comes with a developer community that is a pleasure to work in and with serokell haskell enables us to build reliable performant and maintainable applications for our clients in biotech fintech and blockchain stack builders haskell makes it possible to maintain an edtech platform in 23 languages for more than 70k users from one of the largest multinational financial services corporations features statically typed every expression in haskell has a type which is determined at compile time all the types composed together by function application have to match up if they don t the program will be rejected by the compiler types become not only a form of guarantee but a language for expressing the construction of programs click to expand all haskell values have a type char a char int 123 int fun isdigit char bool you have to pass the right type of values to functions or the compiler will reject the program type error isdigit 1 you can decode bytes into text bytes crypto hash sha1 hash hello bytestring text decodeutf8 bytes text but you cannot decode text which is already a vector of unicode points type error doubledecode decodeutf8 decodeutf8 bytes purely functional every function in haskell is a function in the mathematical sense i e pure even side effecting io operations are but a description of what to do produced by pure code there are no statements or instructions only expressions which cannot mutate variables local or global nor access state like time or random numbers click to expand the following function takes an integer and returns an integer by the type it cannot do any side effects whatsoever it cannot mutate any of its arguments square int int square x x x the following string concatenation is okay hello world the following string concatenation is a type error type error name getline because getline has type io string and not string like name is so by the type system you cannot mix and match purity with impurity type inference you don t have to explicitly write out every type in a haskell program types will be inferred by unifying every type bidirectionally however you can write out types if you choose or ask the compiler to write them for you for handy documentation click to expand this example has a type signature for every binding main io main do line string getline print parsedigit line where parsedigit string maybe int parsedigit c char _ if isdigit c then just ord c ord 0 else nothing but you can just write main do line getline print parsedigit line where parsedigit c _ if isdigit c then just ord c ord 0 else nothing you can also use inference to avoid wasting time explaining what you want do ss decode hello world is decode 1 2 3 return zipwith s i s show i 5 ss is just hello 6 world 7 types give a parser specification for free the following input is not accepted do ss decode 1 2 3 is decode null null null return zipwith s i s show i 5 ss is nothing concurrent haskell lends itself well to concurrent programming due to its explicit handling of effects its flagship compiler ghc comes with a high performance parallel garbage collector and light weight concurrency library containing a number of useful concurrency primitives and abstractions click to expand easily launch threads and communicate with the standard library main do done newemptymvar forkio do putstrln i m one thread putmvar done done second forkio do threaddelay 100000 putstrln i m another thread killthread second msg takemvar done putstrln msg use an asynchronous api for threads do a1 async geturl url1 a2 async geturl url2 page1 wait a1 page2 wait a2 atomic threading with software transactional memory transfer account account int io transfer from to amount atomically do deposit to amount withdraw from amount atomic transactions must be repeatable so arbitrary io is disabled in the type system type error main atomically putstrln hello lazy functions don t evaluate their arguments this means that programs can compose together very well with the ability to write control constructs such as if else just by writing normal functions the purity of haskell code makes it easy to fuse chains of functions together allowing for performance benefits click to expand define control structures easily when p m if p then m else return main do args getargs when null args putstrln no args specified if you notice a repeated expression pattern like if c then t else false you can give this a name like and c t if c then t else false and then use it with the same effect as the original expression get code re use by composing lazy functions it s quite natural to express the any function by reusing the map and or functions any a bool a bool any p or map p reuse the recursion patterns in map filter foldr etc packages open source contribution to haskell is very active with a wide range of packages available on the public package servers click to expand there are 6 954 packages freely available here is a sample of the most common ones bytestring binary data base prelude io threads network networking text unicode text parsec parser library directory file directory hspec rspec like tests attoparsec fast parser monad logger logging persistent database orm template haskell meta programming tar tar archives snap web framework time date time etc happstack web framework yesod web framework containers maps graphs sets fsnotify watch filesystem hint interpret haskell unix unix bindings sdl sdl binding opengl opengl graphics system criterion benchmarking pango text rendering cairo cairo graphics statistics statistical analysis gtk gtk library glib glib library test framework testing framework resource pool resource pooling conduit streaming i o mwc random high quality randoms quickcheck property testing stm atomic threading blaze html markup generation cereal binary parsing printing xml xml parser printer http client http client engine zlib zlib gzip raw yaml yaml parser printer pandoc markup conversion binary serialization tls tls ssl zip archive zip compression warp web server text icu text encodings vector vectors async async concurrency pipes streaming io scientific arbitrary prec nums process launch processes aeson json parser printer dlist difflists syb generic prog sponsors fastly s next generation cdn provides low latency access for all of haskell org s downloads and highest traffic services including the primary hackage server haskell platform downloads and more status io powers https status haskell org and lets us easily tell you when we broke something scarf provides data and insights on the adoption of haskell in order to support efforts to grow the haskell ecosystem and facilitate industry support for the language dreamhost has teamed up to provide haskell org with redundant scalable object storage through their dream objects service digital ocean hosts critical haskell org infrastructure upcloud provides high performance cloud infrastructure that powers ghc s ci pipelines maintenance of this site hosted and managed by haskell org inc a 501 c 3 non profit psst looking for the wiki this is the new haskell home page the wiki has moved to wiki haskell org 2014 2026 haskell org got changes to contribute to the site fork or comment on github