Anders Møller Michael Schwartzbach Erik Ernst Hans Hüttel

Transcription

1 Programming Paradigms 2010 Anders Møller Michael Schwartzbach Erik Ernst Hans Hüttel

2 Aims This purpose of the course is to introduce the student to programming g languages g that support a variety of programming paradigms, such as functional, logic, and concurrent programming to make the student familiar with basic concepts and techniques within the paradigms through practical programming g examples and exercises 2

3 Contents Functional programming languages Haskell λ-calculus Logic programming languages Prolog Advanced object oriented languages AspectJ Scala these languages are chosen to illustrate powerful programming paradigms that are very different from those known from Java or how they may coexist 3

4 Prerequisites Familiarity with a modern object oriented programming language (=Java) 4

5 Why this course? Java is not the only useful programming language... You can never understand one language until you understand at least two. Ronald Searle, artist (1920- ) To know another language is to have a second soul. Charlemagne, king ( ) 5

6 New Programming Languages

7 7

8 8

9 9

10 10

11 11

12 12

13 Programming paradigms A programming paradigm provides a view of program execution or computation Imperative Procedural Object oriented Declarative Functional Logic... A programming language supports one or more paradigms 13

14 Haskell A functional language supports a functional style of programming Haskell is the most popular purely functional, lazy programming language Very different from Java: no notions of objects or classes no modifiable variables no while-loops... but other features compensate Other popular functional languages: ML, Scheme, Erlang, XSLT,... 14

15 λ-calculus A minimal Turing complete functional language (like Turing machines for imperative languages) Discovered by Alonzo Church in 1936 (same year as Alan Turing discovered Turing machines) Foundation o for understanding d functional programming g and type systems 15

16 Prolog A declarative, relational style of programming based on first-order logic programming poga gin logic c Originally intended for natural-language processing, but has been used for many different purposes (esp. for programming artificial intelligence) The programmer writes a database of facts and rules The user then supplies a goal which the system attempts to prove (using resolution and backtracking) 16

17 AOSD and AspectJ Aspect-Oriented Software Development is a very active community which tries to handle some important software engineering challenges Core problem: In "normal" software it is hard to describe each aspect of a problem separately, so the software becomes complex and tangled AOSD solution: add support for aspects to languages In this course AOSD is described mostly through AspectJ, which is mature enough for real-world use and quite popular 17

18 Scala An object-oriented oriented programming language supporting advanced OO concepts, such as, mixins, traits, variance, and abstract type members Supports functional programming natively with higher-order functions, currying, etc., though in a less pure version than Haskell Integrates support for many other things, including Prolog, XML, and regular expressions In this course we will focus on the advanced OO features of Scala 18

19 Course material Slides and example code from lectures Hand-outs and online notes Suggestions for additional literature Course home page: 19

20 AspectJ 20

21 Scala 21

22 Haskell 22

23 Prolog 23

24 λ-calculus 24

25 Week plan Mix of lectures and exercises 5 mandatory hand-ins 25

26 We expect that you are active! Self study! read the suggested chapters prepare for exercise sessions reflect! Your responsibility is to learn... we ll do our best to help 26

27 Exam Multiple choice exam pass / non-pass 27

28 What you will learn from this course (= what we will test in the exam) Classifying and explaining programming language features according to paradigms that go beyond what you know from Java languages language constructs programs Applying paradigmatic features in small programs Relating language constructs in languages that support different paradigms Judging strengths and weaknesses of each paradigm for particular tasks keep this in mind during the course! 28

29 Why bother? Having these skills will make you a better programmer! picking pc gthe right language for agiven task apply appropriate paradigm even if your programming language does not support it well You will become able to quickly learn new programming languages...and you will be able to pass the course 29