Lect 1

Lecture 1

CSC447: Programming Language Concepts

Professor: Karen L. Bernstein

Tuesdays, 5:45 - 9:00 pm

CS&T Center, Room 218

Why study Programming Languages?

learn new languages more easily

choose appropriate languages

program better

design better languages

Overview of Course

Overview of Today’s Lecture

Class Information

Overview of Programming Languages

Describing Syntax

Issues for Imperative Languages

Introduction to Perl

Contact Information

Office: CS&T Center 462

Office Hours:

Monday 4:00 - 5:30, Tuesday 4:00 - 5:30, and by appt

Phone: (312) 362-5315, Fax: (312) 362-6116

Email:

kbernstein@cs.depaul.edu

Course Web Page:

http://www.depaul.edu/~kbernste/csc447

Texts

Ravi Sethi, Programming Languages: Concepts and Constructs, Addison-Wesley, 1996

Randal Schwartz, Learning Perl, O'Reilly & Associates

Bruce Eckel, Thinking in C++, Prentice Hall, 1995

Meyers, Clack and Poon, Programming with Standard ML, Prentice Hall, 1993

Prerequisites:

C Programming (CSC215 or CSC225)

Foundations of Computer Science (CSC415, CSC416, CSC417)

Operating Systems (CSC343)

Computer Architecture (CSC345)

Discrete Mathematics (MAT 140)

Grading

Plagiarism

Students are expected to write their own assignments. The penalty for plagiarism is a grade of F in the course.

Late Policy

Each student is allowed four free late days on the homework assignments for the term. Please use the late days wisely since I will not give out any additional extensions on the assignments.

Web Pages

Course Page

Announcements

Syllabus

Calendar

Lectures

HW Assignments

Useful Links

Video Students

Same due dates and assignments

Must come to Midterm and Final

Get assignments from the web page

Keep in touch (email, telephone, office)

Come to class when you can

Imperative Programming Languages (Algol-like languages)

Fortran I, Fortran II, Fortran IV, Fortran 77, Fortran 90

ALGOL 58, ALGOL 60, ALGOL W

CLU

Pascal, MODULA-2, MODULA-3, Oberon

CPL, BCPL, B, C, ANSI C

BASIC, QuickBASIC, True BASIC, Visual Basic

COBOL, PL/1

ADA

APL

Functional Programming Languages

Lisp, Mac Lisp, Scheme, Common Lisp

ML, Standard ML, CAML

SASL

Miranda

Haskell, Gofer

Object-Oriented Programming Languages

Simula

Smalltalk

C++

Eiffel

Java

Other Programming Paradigms

Logic

Concurrent

Constraint

Visual

Real-time

Some Language Evaluation Criteria

Syntax

Control Structures

Data types

Support for Abstraction

Expressiveness

Type System

Efficiency

Some Influences on Programming Language Design

Application Domain

Available Hardware

Programming Methodology

Implementation Methods

Programming Environments

Structure of Programming Languages

Syntax

Legal programs

Static Semantics

Type system

Dynamic Semantics

Program execution

Programming Language Descriptions

Tutorials

Reference Manuals

Formal Definitions

operational semantics

denotational semantics

axiomatic semantics

Programming Language Implementation

Implementation Strategies

Implementing Debuggers

code specially compiled with symbol table information

debugger instruments object code for breakpoints

Issues:

optimized code

declarative languages

Structure of Programming Languages

Syntax

Legal programs

Static Semantics

Type system

Dynamic Semantics

Program execution

Lexical Structure

identifiers

keywords

operators

seperators

literals

comments

Expressions

Prefix

Postfix

Infix

Associativity

Precedence

Mixfix

Tree Representation of Expressions

BNF (Context Free Grammars)

A set of tokens

A set of non-terminals

A set of rules

A designated start symbol

Issues with Parsing

Concrete vs. Abstract Syntax

Syntactic Ambiguity

Parsing Methods (top-down vs. bottom-up)

Error generation

Extended BNF

Braces, {}, zero or more repetitions

Brackets, [], optional construct

Vertical bar, |, choice

Parenthesis, (), grouping

Syntax Chart

Things you should be able to do with Context-free grammars:

Given a grammar, describe the language

Given a language, write the (E)BNF

Prove that a given grammar is ambiguous

Give a common ambiguous construct

Imperative Programming

Data and Types

State

Flow of Control

Program Composition

Data

imperative languages are based on assignment

size and layout of data structures are determined statically (at compile-time)

storage is allocated and deallocated explicitly

the type declaration determines the data representation

Issues with Types

definition vs. declaration

constant declarations

uninitialized variables

renaming and aliasing

several names, one object

overloading

several objects, one name

Basic Types

characters

integer numbers

precision

signed / unsigned

real numbers (floating point)

precision

Compound Types

Enumeration Types

Arrays

Lists

Sets and bags

Records

What is Perl?
Practical Extraction and Report Language

Perl's author, Larry Wall, describes Perl:

Perl is an interpreted language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information. It's also a good language for many system management tasks. The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal).

Why system administrators are a lot like
Santa Claus (from rec.humor.funny)

When you ask Santa for something, the odds of receiving what you wanted are infinitesimal.

Santa seldom answers your mail.

When you ask Santa where he gets all the stuff he's got, he says, "Elves make it for me."

Santa doesn't care about your deadlines.

Nobody knows who Santa has to answer to for his actions.

Santa laughs entirely too much.

Santa thinks nothing of breaking into your $HOME.

Only a lunatic says bad things about Santa in his presence.

Why look at Perl in this Class?

It is very different from C, C++ and SML

It breaks every rule of "good" language design

It is very popular and useful

It is enough like C, so you can get started quickly

I wrote the homework parsing program in Perl

Pragmatics

How to get Perl

How to run Perl

Perl is interpreted but...

The program is parsed before the first statement is executed

Since it is interpreted, no object code is generated

Our First Perl Program

print "Hello, world!\n"

A little more..

print "What is your name?";

$name = <STDIN>;

chop($name);

print "Hello, $name!";

Data and Types (Perl)

Scalar Data

Numbers

Strings

Scalar Variables start with ‘$’

if uninitialized, have undef value

Arrays/Lists

Array variables start with ‘@’

Associative Arrays

Associative array variables start with ‘%’

Scalar Data

all numbers are the same, everything is stored as a float

strings have no limit on length (can fill all of memory)

single quoted strings

‘hello’

‘don\’t’

‘‘

‘silly \\ me’

‘hello\n’

double quoted (like C)

"hello\n"

"coke\tsprite

Operators

arithmetic basically same as C

with string operators

"hello " . "world" (concatenation)

"hello world" x (2 + 1) (repetition)

no overloading, lots of coercions

"hello world" . (2+1)

"hello world" * (2+1)

binary operators (orthogonality)

$a = $a + 5; $a += 5;

$str .= ‘more stuff’;

two language features that can be combined freely with out restricting each other are said to be orthogonal

Binary operators (orthogonality)

$a = $a + 5; $a += 5;

$str .= ‘more stuff’;

two language features that can be combined freely with out restricting each other are said to be orthogonal

Expressions

have side-effects, can change internal state

assignments have the value of the assigment

chop

$a = 3;

$b = ($a+=2) * ($a-=2);

$a = ‘hello’;

$b = chop($a) . chop($a);

Arrays

(1,2,3), (‘hello’, 13)

printing arrays

$name = ‘Karen’;

print (‘Hello’,$karen,"/n");

more...

@test = (1,2,3);

@test[1] = 2;

$a = @test;

@test2 = (0,@test, 4)