The Haskell Programming Language
An imperative language
Scheme is still imperative
A more realistic example
Factoring out an expression
Haskell: Works with fewer ifs and buts
Overview of Haskell
Haskell’s History
The brevity of Haskell
Quicksort in two lines!
Haskell syntax
Syntax: Haskell vs. Scheme
Hugs98 Haskell Users Gofer System
One gotcha of Hugs98
Learning Haskell
Some simple expressions
When things do not go according to plan...
More errors...
A simple example
Fibonnaci numbers Mathematical notation
Fibonnaci numbers in Haskell Two different approaches
Indentation matters!
Implicit vs. explicit grouping
Explicit grouping is useful at the repl
Function application
Functions with multiple arguments
Currying
Partial application
Specializations
Lambda expression syntax
Functions vs. operators
Other operators
Why use tuples for arguments?
Ackermann function (Wilhelm Ackermann, 1928)
Patterns
Wildcards in patterns
Patterns and case expressions
Conditionals
List shorthands
List comprehension
Compare to using higher order functions
Comprehension instead of nested loops
Values have types
Functions have types too
Built in types
Dynamic vs. Static typing
Advantages of static typing
Static typing rules
Application rule
Cancellation rule
Function rule
List rule
Tuple rule
Length of list of integers
Applying len to [Char]
What does len rely on?
Type variables
Polymorphic functions
Type inference
Type unification
Unification is the intersection of the described types
Evaluation in Haskell
Not all arguments get evaluated
Eager evaluation vs. lazy evaluation
Lazy evaluation is efficient
No need for special forms
Outside-in evaluation avoids intermediate lists