Introduction to Haskell

"I know why you're here. ...why you hardly sleep, why night after night, you sit by your computer."

Features of Haskell

• Purely functional
• Statical typed
• Lazy

1. Purely functional

• Every input has a corresponding output
• f(x) = x² + 1

• Powerful function compositions

  g(x) = x - 1

  g(f(x)) = x²

• PURE

  That means no side effects

  A function will never modify a global variable

  Order doesn't matter!

  Easy concurrency

Functional:

Haskell, Lisp, ML, Scheme, Erlang

Focuses on the high-level "what"

Imperative:

C++, Java, Python, Pascal

Focuses on the low-level "how"

2. Statically Typed

• f x = x² + 1
• f :: Int → Int
• There is never confusion about types

  (Bool, Int, Char, etc)

• Strong formalism. The proof is the code.
• If your code compiles, you're 99% done

3. Lazy?

• Nothing is evaluated unless necessary

　　　　The list will only be sorted enough to find the minimum

• Allows infinite data structures