Haskell

Haskell

1. Is based on LISP programming language

   • Its research was started at 1990 as a committee-designed language
     • The first version was released at 1998 as Haskell 98

2. The first and most important compiler is Glasgow Haskell Compiler

   • You can download it and start learning for free
   • It comes with an interactive environment (GHCi)
     • And with a project build tool (Cabal)
       • And a dependency manager
     • Enter it using "ghci" command
       • Exit using the ":q" command
       • If you see
         • Prelude>
           • Means only Haskell standard library is loaded
         • *Main>
           • A project is compiled and loaded

3. The Hello World Program

   • main = putStrLn "Hello, World"
     • The "putStrLn" function receives a String as argument and print it out to the standard output followed by a new line (\n)

4. The Syntax

   • Program entry point does not have arguments (like C)
   • Functions
     • functionName arg1 arg2 = code
     • Function and argument names must start with lowercase letter
   • Comments
     • Instead of "//" we use "--"
   • User defined types
     • type String = [Char]
     • Whenever the compiler sees String as a type, it replaces with with [Char]
     • Completely new data type
       • data Color = Red | Green | Blue
       • Kinda Java enums
   • if statement
     • Guards
       • Kinda multi-way if statements (else if)
   • Lists
     • Generate lists using [X..Y]

5. Types

   • Numeric (Num)
     • Integer
     • Floating
     • Double
   • Compiler has type inference
   • List
     • String
   • Char
   • Boolean
   • Tuple
   • Typeclasses
     • Like Java interfaces
     • All types must start with uppercase letter
     • You can define new typeclasses
     • Allow us to attach a set of functions to a data type
     • Monad is a typeclass

6. Allows cleaner and shorter implementations

   • binary functions to inline functions
     • Enclose them between backticks (`)
       • a `mod` b
   • The Maybe type
     • Returns None or a value
       • Forces programmer to handle both escenarios

7. Create a project

   • stack new test
     • Creates a new project called "test"
       • Run it with "stack exec"

8. Conclusion

   • Haskell has a lot of features
     • Cannot cover them all here

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