Something about me

• C++ - 4 years
• Haskell - 2 years
• No formal education in abstract mathematics ;)
• Work on some haskell packages (hsua, hlint-test, freer-effects)

Why functional programming matters

• Functions are first class citizens
• Partial application
• Immutability
• Sum types
• Laziness
• Pattern matching
• Mostly strongly typed
• Reference to a great talk

Academic haskell vs real world haskell

• There is not much deference

Examples of some haskell projects

• Universal document converter pandoc
  • 56000 loc
• Distributed file synchronization system git-annex
  • 58000 loc
• Quake like game Frag
  • only 5582 loc
• Whole haskell infrastructure
  • Hackage
  • Hoogle
  • Stackage
  • GHC

Ixcom - Story of our first product

• Telephony exchange
• 70000 loc
• Bunch of APIs: REST API, Json RPC
• DLS for phone number description
• Build on top of asterisk
• The core never crashed

Vision - Story of our second product

• Image processing
• Extremely fast developement
• Zero tests
• We are still waiting for first bug to arrive

Functional jobs

• Functional job in general is obtainable
• Haskell job in Czech Republic (not so much)
• Haskell job in the world (lot of opportunities)

Hiring haskellers

• Easy to find
• People are over qualified
• People accept to lower salary

Great books

• Haskell Programming from first principles
• Real World Haskell
• Learn You a Haskell for Great Good!
• List of some free haskell books

News and connections

• r/haskell
• IRC channels on freenode
  • #haskell
  • #haskell-embedded
• https://fpchat-invite.herokuapp.com/
• pair-programming

Invitation to FPBrno

• meetup.com/fpbrno/
• Next talk
  • Topic: Reason ML & Benchmarking in Elixir
  • Date: Tuesday, May 22, 2018

Other areas where haskell can be used

• clash - compilation haskell on FPGA
• ivory-tower - EDSL for C -> embedded devices
• quantum computers

Some useful libraries

• acid
• aeson
• containers
• lenses
• megaparsec
• monad-logger
• mtl
• persistent
• servant
• template-haskell

Servant example

type ItemApi =
    -- GET /item
    "item" :> Get '[JSON] [Item] :<|>
    -- GET /item/:itemId
    "item" :> Capture "itemId" Integer :> Get '[JSON] Item

getItems :: Handler [Item]
getItems = return [exampleItem]

getItemById :: Integer -> Handler Item
getItemById = \case
    0 -> return exampleItem
    _ -> throwE err404

server :: Server ItemApi
server = getItems :<|> getItemById

Taken form example-servant-minimal.

freer-effects example

example

Questions?

• Thank you for your attention.
• Slides will be available at github.com/siprj/haskell-seminar-presentation-spring-2018