Summer 02-03 Programming Language Concepts 1

Programming Language Concepts(CS 360)

Lecture 1: Overview, Grammars, and Little Languages

Jeremy R. Johnson

(Guest Lecturer)

Summer 02-03 Programming Language Concepts 2

Basic Info

• Instructor– Sam Moelius– Email: smoelius@cs.drexel.edu– Office Hours: TBD

• Text– Concepts of Programming Languages, 5th Ed.– Robert W. Sebesta– Addison Wesley

• Web Page– TBD

• Mailing List– TBD

Summer 02-03 Programming Language Concepts 3

Course Description

Introduces the design and implementation of modern programming languages: formal theory underlying language implementation; concerns in naming, binding, storage allocation and typing; semantics of expressions and operators, control flow, and subprograms; procedural and data abstraction; functional, logic, and object-oriented languages. Students will construct an interpreter for a non-trivial language.

Summer 02-03 Programming Language Concepts 4

Course Prerequisites

• CS 171 (Prog. I), 172 (Prog. II), and 260 (Data structures)

• Comfortable with an object-oriented language (ideally should have seen at least two languages)

• Ideal:– CS 281 (Systems Architecture I) – understanding of the underlying of

basic computer architecture (assembly language, machine organization)– CS 270 (Foundations of Computer Science) – should be comfortable with

the mathematical tools used to describe and analyze programming languages (logic, recursion – material on finite state machines and grammars useful but will be covered in this class)

Summer 02-03 Programming Language Concepts 5

Course Themes

• Tools to evaluate design of languages• Tools for describing and analyzing languages

– syntax– semantics

• Tools to design new languages• Programming Paradigms• Implementation of programming languages

Summer 02-03 Programming Language Concepts 6

Course Objectives

1. Understand how to compare and evaluate different programming languages and know what factors need to be taken into account.

2. Be comfortable with the major programming paradigms and be able to use at least one language from each paradigm.

3. Understand some of the issues involved in implementation of programming languages; this should help them program more efficiently.

4. Be familiar with elementary concepts of formal language theory such as context-free grammar.

5. Be able to formally specify the syntax of programming languages.

6. Be familiar with the essentials of lexical analysis and elementary parsing procedures.

7. Understand dynamic and static scope, dynamic and static binding and the issues they give rise to.

8. Understand the advantages and disadvantages of strong/weak type checking.

9. Understand the different methods of parameter passing and how they might be implemented and understand some of the issues involved in calling subroutines.

10. Understand generic programming.

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Tentative Topics

1. Week 1: Overview and introductions to grammars (ch. 1 & 3)2. Week 2: Functional Languages (ch. 15)3. Week 3: Logic Programming Languages (ch. 16)4. Week 4: Syntax, Types, Scanning, and Parsing (ch. 3-5)5. Week 5: Midterm (more on types and type checking)6. Week 6: Data types and Memory allocation (ch. 6)7. Week 7: Program semantics and interpreters (ch. 3)8. Week 8: Control Structures. Iteration versus Recursion and their

implementation. Templates in C++ and generic programming and its advantages and pitfalls (ch. 7-9).

9. Week 9: Subroutines and Parameter Passing Methods, Implementing subroutines (ch. 9-10).

10. Week 10: Abstract data types and object-oriented programming (ch. 11-12)

Summer 02-03 Programming Language Concepts 8

Course Benefits

• Easier to express ideas• Improved background for selecting appropriate languages• Easier to learn new languages• Understand the significance and impact of language choices

and constructs• Design new languages (little languages, interface

specifications, protocols)• Overall advancement of computing

Summer 02-03 Programming Language Concepts 9

Grading Policy

• Assignments (Programming & Description & Evaluation)– 5 @ 10% each

• Midterm Exam– 25%

• Final Exam– 25%

Grades will be determined using a curve with the weighted average equal to a B provided the average shows understanding of the material.

All work must be completed independently unless explicitly stated other wise. Not following this rule is subject to receiving a 0 for the first offense and subsequent offenses may lead to a lower or failing grade.

Summer 02-03 Programming Language Concepts 10

Outline (Ch. 1)• Programming Domains• Programming Paradigms• Language Evaluation Criteria

– Readability– Writability– Reliability– Cost

• Influences on language design– Computer architecture– Programming methodologies

• Language categories– Imperative– Functional– Logic– Object-oriented

• Implementation methods– Interpreter– Compiler– Hybrid

Summer 02-03 Programming Language Concepts 11

Programming Domains

• Scientific Computing– FORTRAN– C, C++– Matlab, Maple, Mathematica

• Business Applications– COBOL– Spreadsheet, DB, SAP

• Systems Programming– assembly– PL/S, BLISS, C

• Scripting Languages– sh, ksh, bash– awk, perl, python

• Artificial Intelligence– lisp, prolog

• Special-purpose languages

Summer 02-03 Programming Language Concepts 12

Programming Paradigms

• Imperative (procedural)– Algol, C, FORTRAN, Pascal

• Data Abstraction– Modula-2

• Object Oriented– Simula 67, Smalltalk, C++, java, Ada 95, Eiffel

• Functional– Lisp, Scheme, ML

• Logic (declarative – rule based)– prolog

• Parallel• Hardware Description Languages• Markup• Special-purpose

Summer 02-03 Programming Language Concepts 13

Evaluation Criteria

• Readability– Simplicity– Orthogonality– Control statements– Appropriate data types– Syntax considerations

• Writability– Simplicity and orthogonality– Support for abstraction– Expressivity

• Reliability– type checking– exception handling– Aliasing

• Cost– readability and the learning curve– writability and naturalness of the language for the application– compilation and execution time

Summer 02-03 Programming Language Concepts 14

Compilation

LexicalAnalyzer

SyntaxAnalyzer

IntermediateCode

Generation

Symbol Table

Optimizer

CodeGenerator

ComputerLexical Units

Parse Tree

Intermediate Code

Machine Language

User Inputs

Source Program

Results

Summer 02-03 Programming Language Concepts 15

von Neumann Architecture

Control

CPU

Memory

ALU I/O

Fetch-Execute Cycle

1. Initialize PC, Registers2. Repeat

1. Fetch Instruction2. Increment PC3. Decode Instruction4. Execute Instruction

Summer 02-03 Programming Language Concepts 16

Interpretation

Source Program

InterpreterUser Inputs

Results