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Programming Paradigms

Programming Paradigms. Jigar Gaglani. Paradigms. Programming paradigm is a fundamental style of computer programming Paradigms differ in concepts and abstractions used to represent the elements of program. Four main programming paradigms. Procedural/Imperative Functional Logic

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Programming Paradigms

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  1. Programming Paradigms Jigar Gaglani

  2. Paradigms Programming paradigm is a fundamental style of computer programming Paradigms differ in concepts and abstractions used to represent the elements of program

  3. Four main programming paradigms Procedural/Imperative Functional Logic Object-Oriented

  4. Imperative Programming Derived from latin word imperare means “to command” It is based on commands that update variables in storage Is a programming paradigm that describes computation in terms of statements that change a program state.

  5. Contd.. It defines sequences of commands for the computer to perform Imperative programming is characterized by programming with a state and commands

  6. Contd.. In imperative programming, a name may be assigned to a value and later reassigned to another value. A name is tied to two bindings, a binding to a location and to a value. The location is called the l-value and the value is called the r-value.

  7. Contd.. • For example, • X := X+2 • Assignment changes the value at a location. • A program execution generates a sequence of states

  8. Unstructured Commands • The unstructured commands contains: • assignment command, • sequential composition of commands, • a provision to identify a command with a label, • unconditional and conditional GOTO commands

  9. Contd.. • The unconditional goto command has the form: • goto LABELi • The sequence of instructions next executed begin with the command labeled with LABELi. • The conditional goto command has the form: • if conditional expression then goto LABELi

  10. Structured Programming The goal of structured programming is to provide control structures that make it easier to reason about imperative programs.

  11. Contd.. • an IF statement corresponds to an If condition then command and a DO statement corresponds to a While condition Do command. • IF guard --> command FI=if guard then command • DO guard --> command OD=while guard do command 

  12. Contd.. An imperative program can only be understood in terms of its execution behavior.  Thus, the whole program may need to be examined in order to understand even a small portion of code.

  13. Procedural Programming The program is built from one or more procedures It provides a programmer a means to define precisely each step in the performance of a task.

  14. Possible Benefits The ability to re-use the same code at different places in the program without copying it. An easier way to keep track of program flow than a collection of "GOTO" or "JUMP" statements

  15. Declarative Programming Declarative programming is a non-imperative style of programming Does not explicitly list command or steps that need to be carried out to achieve the results.

  16. A great example of declarative Vs. imperative programming • For example: • List<int> collection = new List<int> {1,2,3,4,5 }; • Imperative programming • List<int> results = new List<int>(); • foreach(var num in collection) { if (num % 2 != 0) results.Add(num); }

  17. Contd.. • Declarative programming • var results = collection.Where( num=>num%2 != 0); • Does not step through the collection

  18. Example languages • Procedural • Assembler, Fortran, Cobol, C, etc • Non-Procedural • SQL, Visual Basic, etc etc.

  19. Functional Programming It treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style

  20. Contd.. Functional programming is all about expressions. Functions are used as objects in FP. Functional Programming is about abstraction and reducing complexity

  21. Example spam = ['pork','ham','spices'] numbers = [1,2,3,4,5] def eggs(item): return item map(aFunction, aSequence)

  22. Contd.. • L = map(eggs, spam) print L • Same thing could have been done by:  • for i in spam: L.append(i) print L

  23. Contd.. • If we want to create a new list of only odd numbers : • def isOdd(n): return (n%2 != 0) • L = filter(isOdd, numbers) • print L • Alternatively • def isOdd(n): return (n%2 != 0) • for i in numbers: • if isOdd(i): • L.append(i) • print L

  24. Logic Programming Paradigm It is the use of mathematical logic for computer programming The problem-solving task is split between the programmer and theorem-prover

  25. Contd.. • To study logic programming means to study proofs. • It is based upon the fact of a backwards reasoning proof • Eg. : • If B1 and … and Bn then H

  26. Prolog Prolog is a general purpose logic programming language associated with artificial intelligence and computational linguistics It is based on Facts and Rules

  27. Facts • Simple Facts: • Facts either consist of a particular item or a relation between items. • For Eg : • the fact that it is sunny is represented by writing the program : sunny. • We can now ask a query of Prolog by asking • ?- sunny.

  28. Facts with Arguments • facts consist of a relation and the items that this refers to, called arguments • A general model is shown below: relation(<argument1>,<argument2>,....,<argumentN> ).

  29. Contd.. • The basic Prolog terms are an integer, an atom, a variable or a structure. • Example : • likes(john,mary). • In the above fact john and mary are two atomes.

  30. Rules • Consider the following sentence : • 'All men are mortal' • We can express this as : • mortal(X) :- human(X). • Let us define the fact that Socrate is a human. • mortal(X) :- human(X).  human(socrate).

  31. Contd.. • Now if we ask to prolog : • ?- mortal(socrate). • What prolog will respond ? • Why ?

  32. Negation as failure • One of Prolog's most useful features is the simple way it lets us state generalizations. • Example: • enjoys(vincent,X) :- burger(X). • Vincent enjoys burgers, except Big Kahuna burgers, how do we state this in Prolog?

  33. Contd.. As a first step, let's introduce another built in predicate fail/0 fail enables us to write some interesting programs, and in particular, it lets us define exceptions to general rules

  34. Contd.. • Consider the following code: • enjoys(vincent,X) :- big_kahuna_burger(X),!,fail.enjoys(vincent,X) :- burger(X).burger(X) :- big_mac(X).burger(X) :- big_kahuna_burger(X). big_mac(a).big_kahuna_burger(b).big_mac(c).

  35. Contd.. The first two lines describe Vincent's preferences. The last 4 lines describe a world containing 3 burgers, a, b, and c

  36. Contd.. • This is what happens: • ?- enjoys(vincent,a).yes?- enjoys(vincent,b).no?- enjoys(vincent,c).yes

  37. Contd.. • The key is the combination of ! and fail in the first line • This cut-fail combination lets us define a form of negation called negation as failure • General notation: • neg(Goal) :- Goal,!,fail.neg(Goal).

  38. Contd.. • For any Prolog goal, neg(Goal) will succeed precisely if Goal does not succeed. • Using our new neg predicate, we can describe Vincent's preferences as: • enjoys(vincent,X) :- burger(X), neg(big_kahuna_burger(X)).

  39. Object Oriented Paradigm Object-oriented programming (OOP) is a programming paradigm that uses "objects" – data structures consisting of datafields and methods together with their interactions – to design applications and computer programs.

  40. Contd.. It is a paradigm where we focus real life objects while programming any solution. We actually write behaviours of our programming objects, those behaviours are called methods in objected oriented programming.

  41. Principal advantage They enable programmers to create modules that do not need to be changed when a new type of object is added. A programmer can simply create a new object that inherits many of its features from existing objects.

  42. Fundamental Concepts Class Object Instance Method Message passing Inheritance Abstraction Encapsulation Polymorphism Decoupling

  43. Main features • Encapsulation: • a logical boundary around methods and properties • Inheritance • Re-usability • method overloading and overriding • Information Hiding • is achieved through "Access Modifiers"

  44. OOP vs Functional Programming vs Procedural What are the differences between these programming paradigms, and are they better suited to particular problems or do any use-cases favor one over the others?

  45. Video

  46. Contd..

  47. Contd..

  48. References http://en.wikipedia.org/wiki/Imperative_programming http://www.emu.edu.tr/aelci/Courses/D-318/D-318-Files/plbook/imperati.htm http://en.wikipedia.org/wiki/Procedural_programming http://www.ocaml-tutorial.org/functional_programming http://boklm.eu/prolog/page_4.html http://cs.union.edu/~striegnk/learn-prolog-now/html/node90.html

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