COSC 4P41 Functional Programming

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COSC 4P41Functional Programming

• Instructor Michael Winter
• Office J323
• Office Hours Tue Wed 1000am - 1200pm
• email mwinter_at_brocku.ca
• Webpage http//www.cosc.brocku.ca/Offerings/4P4
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• Course Description (Brock Calendar)
  
  Introduction to
  functional programming using the languages
  Haskell. Topics include all data types, type
  inference, pattern-matching, recursion,
  polymorphism, higher-order functions, lazy vs
  eager evaluation, modules and monads.
• Prerequisites None
• Haskell http//www.haskell.org
• course procedures
• plagiarism

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Textbooks

• Main Text
• Haskell, The Craft of Functional Programming, 
  2nd edition, S. Thompson, Addison - Wesley
  (1999), ISBN 0-201-34275-8
• Supplemental Texts
• The Hugs 98 User Manual, Mark P Jones, Alastair
  Reid, online documentation.
• Real World Haskell, Bryan O'Sullivan, John
  Goerzen, Don Steward, O'Reilly (2009), ISBN
  978-0-596-51498-3
• The Haskell School of Expression, P. Hudak,
  Cambridge University Press (2000), ISBN
  0-521-64408-9

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Course Work

• Marking Scheme
• Programming Assignments (2x10,2x20) 60
• Final Exam (oral) 40
• Programming Assignments
  Number Due Late
• 1 Sep 28 _at_ 100pm Sep 30 _at_ 100pm
• 2 Oct 19 _at_ 100pm Oct 21 _at_ 100pm
• 3 Nov 09 _at_ 100pm Nov 11 _at_ 100pm
• 4 Nov 30 _at_ 100pm Dec 02 _at_ 100pm
• Registration for final exam   Mid of October
  (Office hours or after class)
• Final Exam (oral, 30min each)   Monday, December
  07, 2009

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• Assignments will be available online. Submission
  is electronically. Details see webpage.
  Assignments will be returned by email.
• Assignments are due at the times specified above
  and will be accepted late until the indicated
  time, subject to a penalty of 25. After the late
  period, assignments will not be accepted.
• A mark of at least 40 on the final exam is
  required to achieve a passing grade in this
  course.
• Assignments will be carefully examined regarding
  plagiarism. Cases of suspected plagiarism will be
  dealt with according to the University
  regulations and Departmental procedures.
• Consideration regarding illness for assignment
  submission or test dates will only be considered
  if accompanied with the completed Departmental
  Medical Excuse form.

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Course Outline
Week Date Book/Chapt. Topics
1 Sep 14/16 1 13 Introduction to Functional Programming
2 Sep 21/23 1 45 Recursion and Data Types
3 Sep 28/30 1 67 Lists
4 Oct 05/07 1  9-10 Patterns of Computation, Functions as Values
5 Oct 14/19 1 12-13 Overloading, Type Classes, Type Checking
6 Oct 21/26 1 14-15 Algebraic Types
7 Oct 28/Nov 02 1 16 Abstract Data Types
8 Nov 04/09 1 17 Lazy Evaluation
9 Nov 11/16 1 18 Programming with Actions
10 Nov 18/23 1 8, 14.7 17.9 Reasoning about Programs
11 Nov 25/30 1 8, 14.7 17.9 Reasoning about Programs II
12 Dec 02/03 2 7 Hugs Language extensions, Review
October 12 is Thanksgiving, no classes. Make up
on December 03.
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Imperative languages

• Von Neumann model
• store with addressable locations
• machine code
• effect achieved by changing contents of store
  locations
• instructions executed in sequence, flow of
  control altered by jumps
• imperative language
• variable corresponds to store location
• instructions executed in sequence, flow of
  control altered by conditional and loop
  statements
• efficient implementation since close to design of
  conventional computers

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Functional languages

• computational model lambda calculus
• mathematical functions domain, range
• functional languages achieve effect by applying
  functions
• functional vs. imperative languages
• store location
• assignment statement vs. application of a
  function (expressions)
• side-effects
• aliasing
• referential transparency

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Features of functional languages

• usually strongly typed (modern languages)
• algebraic type definitions
• mathematical based notation
• no (implicit) pointers
• higher-order functions
• can accept functions as parameters
• can return functions as results
• recursion as a basic principle
• application of rewrite rule
• function call replaced by code body
• run-time overhead ? garbage collection
• slogan define what to do, not how to do

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What is a function?
A function is something which produces an output
value depending on the input value(s).
A type is a collection of values. Usually
functions are considered to take values of
specific types as input, and produce values of
another type.
A functional program is basically a list of
definitions of functions.
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Definitions

• Haskell definitions are of the form
• name type
• name expression
• Examples
• size Int
• size (1213)4
• square Int -gt Int
• square n nn

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• -
  
• FirstScript.hs
• Simon Thompson, June 1998
• The purpose of this script is
• - to illustrate some simple definitions
  
• over integers (Int)
• - to give a first example of a script.
• 
  -
• -- The value size is an integer (Int), defined to
  be
• -- the sum of twelve and thirteen.
• size Int
• size 1213

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• 
  
• FirstLiterate.lhs
• Simon Thompson, June 1998
• The purpose of this script is
• - to illustrate some simple definitions
• over integers (Int)
• - to give a first example of a literate script.
• 
  
• The value size is an integer (Int), defined to be
  the sum of
• twelve and thirteen.
• gt size Int
• gt size 1213

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The Booleans

• type Bool
• operations
• exOr Bool -gt Bool -gt Bool
• exOr x y (x y) not (x y)

and
or
not not
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The integers

• type Int range 21474836482147483647
• type Integer range unbounded
• operations

sum
product
raise to the power
- difference
div whole number division
mod remainder
abs absolute value
negate change sign
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Relational operators and overloading

• () for integers and Booleans. This means that
  () will have the type
• Int -gt Int -gt Bool
• Bool -gt Bool -gt Bool
• Indeed t -gt t -gt Bool if the type t carries an
  equality.
• () Eq a gt a -gt a -gt Bool

gt greater than
gt greater than or equal to
equal to
/ not equal to
lt less than or equal to
lt less than
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The rational numbers

• type Rational (import Ratio)
• operations
• and , , -, negate, abs

Integer -gt Integer -gt Rational
numerator the numerator
denominator the denominator
fromInteger Integer -gt Rational
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The characters

• type Char
• a
• \t tab
• \n newline
• \\ backslash
• \ single quote
• \ double quote
• \97 character with ASCII code 97, i.e., 9

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Layout

• mystery x xx
• x
• 2
• next x
• fun v1 v2 vn
• g1 e1
• g2 e2
• otherwise er

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Operators and Do-it-yourself operators

• () Int -gt Int -gt Int
• () 2 3 2 3
• 2 max 3 max 2 3
• Operator symbols !,,,,,,,.,/,lt,,gt,?,\,,
  ,,-,
• () Int -gt Int -gt Int
• x y
• x gt y y
• otherwise x