evaluation of programming languages

7/31/2019 Evaluation of Programming Languages

1/29

Evaluation of ProgrammingLanguages

Asst. Prof. Dr. Ahmet Sayar

Spring-2012

Kocaeli University

Computer Engineering Department

Principles of Programming

Languages


2/29

Programming Domains

Scientific applications Large number of floating point computations

FORTRAN and ALGOL 60

Business applications

Produce reports, use decimal numbers and characters

COBOL

Artificial intelligence

Symbols rather than numbers manipulated

LISP (1965), Logic programming using PROLOG (1997), SCHEME (adialect of LISP)


3/29

Programming Domains Systems programming

Need efficiency because of continuous use

IBM PL/S (a dialect of PL/I 1970s)

UNIX (1989 in C)

Scripting languages

Put a list of commands in a file to be executed

The first language named sh (shell)

Ksh (developed at Bell lab -1995)

Tcl (developed at Berkeley -1994)

Perl (2000)

combination of sh and awk Popularity increased by www - good for CGI programming

JavaScript (developed by Netscape)

Special-purpose languages


4/29

Readability

Control statement Earlier version of FORTRAN does not have a loop control,

instead the goto statement are used to implement loops

In FORTRAN 77 style:

L1:

if (inc > 20) go to Out;

L2:

if (sum > 100) go to Next;

sum+ = inc;

go to L2;

Next:

inc++;

go to L1;

Out:

In C:

while (inc 20) {

while (sum 100) {

sum+= inc;

}

inc++;}


5/29

Language Evaluation Criteria Writability

Factors: Simplicity and orthogonality

Support for abstraction Process and data abstractions

Expressivity Count++ or count=count+1 ?

Reliability Factors:

Type checking

Exception handling c? c++? Java?

Aliasing

Readability and writability


6/29

Language Evaluation Criteria

Cost Categories

Training programmers to use language

Writing programs

Compiling programs

Executing programs

Language implementation system

Reliability

Maintaining programs

Others: portability, generality, well-definedness


7/29

Language Design Trade-Offs

Reliability vs. cost of execution

Example: Java demands all references to array elements be checked

for proper indexing, which leads to increased execution costs

Writability (flexibility) vs. reliability

Example: C++ pointers are powerful and very flexible but are

unreliable


8/29

Influences on Language Design

Computer architecture: Von Neumann

We use imperative languages, at least in part,because we use von Neumann machines

Data and programs stored in same memory Memory is separate from CPU

Instructions and data are piped from memory toCPU

Basis for imperative languages Variables model memory cells

Assignment statements model piping

Iteration is efficient


9/29

Von Neumann Architecture


10/29

Influence on Language Design Programming Methodologies

Procedure-oriented programming (late 60s - early 70s)

Cost shift : from hardware to software development

Programs are executed through successive procedure calls

Data-oriented programming (late 70s)

Focuses on using abstract data types to solve problems

The first language supporting Simula 67

Object-oriented programming (early 80s)

Data abstraction, inheritance and dynamic binding The first language supporting SmallTalk


11/29

Programming Paradigms

1. Imperative

Structured Programming

Object Oriented Programming

Distributed Programming

2. Declarative

Functional Programming

Logic Programming

Database Languages


12/29

1. Imperative Languages

Describes computation in terms of statements that change a

program state

Central features are variables, assignment statements, and

iteration

Imperative programs define sequences of commands for the

computer to perform

Control is the responsibility of the programmer

It is much more in tune with the computer community's wayof thinking

C, Fortran, Pascal, Pascal


13/29

2. Declarative Languages

Expresses whatthe program should

accomplish without prescribing howto do it in

terms of sequences of actions to be taken

Expresses the logic of a computation without

describing its control flow

No assignment for the variables

Lisp, Scheme, SQL


14/29

1.1. Structured Programming Structured programs are often composed of simple, hierarchical program

flow structures. These are sequence, selection, and repetition. It has a syntax for enclosing structures between bracketed keywords, such

as an if-statement bracketed

It is most famous for removing or reducing reliance on the GOTOstatement.

Well known examples: C, Fortran, PL/I, Pascal, Cobol, Ada.


15/29

1.2. Object Oriented Programming

An abstraction and generalization of imperative programming.

Involves collections of objects each with a state and a set ofoperations to transform the state.

Focuses on data rather than on control.

As in the real world, objects interact so object-orientedprogramming uses the metaphor of message passing tocapture the interaction of objects.

Encapsulate data objects with processing

Inheritance and dynamic type binding

Grew out of imperative languages

C++, Java


16/29

Object Oriented Programming


17/29

1.3. Distributed Programming

Distributed computing is a field of computer science that studiesdistributed systems.

A distributed system consists of multiple autonomous computers thatcommunicate through a computer network

A computer program that runs in a distributed system is called a

distributed program, and distributed programming is the process ofwriting such programs

There are several autonomous computational entities, each of which hasits own local memory.

The entities communicate with each other by message passing.

The computational entities are called computers or nodes.

WHY Distributed systems ?


18/29

Distributed Programming


19/29

2.1. Functional Programming 1

Functional programming is a style of programming in whichthe basic method of computation is the application offunctions to arguments.

Functional programming involves creating and manipulating

functions to build up larger programs. The abstract nature of functional programming leads to

considerably simpler programs.

Ex: summing the integers from 1 to 10

Sum[1..10] in Haskell

The computation method is function application

Examples: Lisp, Scheme, ML


20/29

Functional Programming Ex: Scheme 2

In a functional programming language, certain functions, calledprimitive functions or just primitive, are defined as part of thelanguage. Other functions can be defined and named by theprogrammer. To define the doubling function using Scheme youcould say

(define (double x)

( * 2 x)

Scheme responds immediately to a function invocation bydisplaying the result so the following will occur using thenumbers 5 and 7.

(double 5)

10(double 7)

14

What is the difference between a mathematical function and thenotion of a function used in imperative programminglanguage?


21/29

Functional Programming - 3

Involves no notion of variable or assignment

to variables

Concentrates on values and functions instead

of memory locations

Repetitive operations are not expressed by

loops but by recursive functions


22/29

Functional Programming - 4

Common functional programming language

and its gcd application is given below


23/29

2.2. Logic Programming - 1

A set of axioms, or rules, defining relationships between objects

The art of logic programming is constructing concise and elegant programs

that have the desired meaning

There are three basic statements: facts, rules and queries. There is a single

data structure: the logical term Logic programming is, basically, the use of mathematical logic for

computer programming.

Rule-based

No special order in rules

Prolog


24/29

Logic Programming - 2

A program consists of a set of statements that describe what

is true about a desired result, as opposed to giving a particular

sequence of statements that must be executed in a fixed

order to produce the result

Prolog is widely used logic programming

Example code for gcd


25/29

Logic Programming - 3

1-25


26/29

Logic Language: PROLOG - 4

The best-known logic programming language is Prolog. Prolog programs consists of facts and rules. A fact expresses a property about a

single object or a relationship among several objects. As an example, a Prologprogram was written for American history. The example consisted of which U.S.presidents were in office when certain events occurred and in the chronologyorder of those presidents terms in office. Here are the short list of facts(declarations):

president (lincoln , gettysburg_address).president (lincoln, civil_war).president (nixon. first_moon_landing).president (jefferson, lewis_and_clark).president (kennedy, cuban_missle_crisis).president (fdr, world_war_II).

before (jefferson, lincoln).before (lincoln, fdr).before (fdr, kennedy).before (kennedy, nixon).


27/29

Exercises

?-before(lincoln, fdr)

?-president (jefferson, lewis_and_clark)

?-before(first_moon_landing ,

cuban_missle_crisis)


28/29

2.3. Database Programming

SQL

Definition Language DDL

Manipulation Language DML

Can be embedded in other languages


29/29

Questions?

In what language UNIX is written? What is aliasing?

What is exception handling?

What does it mean for a program to be reliable?

Which is faster, compiler or interpreter?

What does a linker do?

What arguments can you make for the idea of a

single language for all the programming domains?

Describe the advantages and disadvantages of some

programming environments you have used.

evaluation of programming languages

Documents