CS 403 Compiler Construction Lecture 3 Lexical Analysis [Based on Chapter 1, 2, 3 of Aho2]


 Briana Nichols
 3 years ago
 Views:
Transcription
1 CS 403 Compiler Construction Lecture 3 Lexical Analysis [Based on Chapter 1, 2, 3 of Aho2] 1 What is Lexical Analysis? First step of a compiler. Reads/scans/identify the characters in the program and groups them into tokens Tokens are of the form <tokenname, attributevalue> or <tokenname> Lexeme: examples of tokens Example 1: a=b+c becomes <id,1> <=> <id,2> <+> <id,3> 5 lexemes (a, =, b, +, c) 5 tokens Tokens are stored in a symbol table 2 1
2 What is Lexical Analysis? Example 2: Position = initial + rate * 60 <id,1> <=> <id,2> <+> <id,3> <*> <60> White space deleted in lexical analysis. No white space here 3 How to identify tokens? By finding patterns, because tokens have many different patterns. Patterns: different forms of tokens. Examples of patterns: Pattern 1: keywords: if, else, system, out, in, Pattern 2: operators: +, , %, *, >=, <>, ==,<=, Pattern 3: variables: a, xyz, a_b, p, q2, _e, _001abc, Pattern 4: numbers: 23, 3.45, 7, 0 Other patterns.. Example: if (speed > 130 ) system.out.println( Ticket 300 SAR ); This java code has many token patterns: if, speed, >, 130, system,., out, println, (,, Ticket 300 SAR,, ), ; 4 2
3 Regular Expressions How to identify token patterns? Answer: By regular expressions Regular expression [we already learned this in CS 301: Theory of computation]: is a regular expression denoting the empty set { }. Every symbol a is a regular expression denoting {a}. If r 1, r 2 are two regular expressions then: r 1 * denotes zero or more occurrences of r 1 r 1 + denotes one or more occurrences of r 1 r 1 r 2 denotes concatenation r 1 r 2 denotes either r 1 or r 2 Example: regular expression for integers Suppose that, in a programming language, integers are like these: 2, 999, 50, +34, , +0, 0, +000 So, regular expression for them: integer (+ ) ( ) + Example: regular expression for decimals Suppose that decimals are like these: 0.0, , , So, regular expression for them: decimal integer.( ) + Regular Expressions Example: Regular expression for identifiers of C language Identifiers (also called variables) in C languages are like these (similar to Java): a, a_1, a2, _,, _p, y98, Masud_Hasan, Identifiers are used in statements like this: a = a + 1; _p = b*a_1; But 55, 23masud, 0, 2, are not identifiers Identifier must start with a letter or _, then a letter, _, or digit can repeat So, the regular expression for identifier is: id (letter _) (letter _ digit)* But, we also need to say what is letter and what is digit? Complete regular expression is: letter A B C Z a b c z digit id (letter _) (letter _ digit)* Example: Regular expression for White Space ws (blank tab new line) + 6 3
4 Transition Diagrams Transition diagrams: An intermediate step after regular expression, pictorial, like a graph, easier way to understand patterns. Accepter (says yes if match). Example: Transition diagram for relational operators (relop) Relational operators (relop) in Pascal are: =, <, >, <>, <=, >=  Circle means state  Double circle means accepting state Equivalent regular expression: relop < > = < > < = >= 7 Finite Automata (learned in CS 301) Finite Automata: They are graphs, like transition diagrams But, they are recognizer, that means, they say yes or no. If string finished and final state, then YES. If string finished and not final state, or final state but string not finished, then NO. Two types: NFA and DFA are same. For any regular expression, there are equivalent NFA and DFA. 8 4
5 Example: NFA for (a b)*abb NFA Try some examples for this NFA: YES: aaaabb, ababababb, abb,. NO: a, bb, b, abab, abbbb,. 9 Example: NFA for aa* bb* NFA means transition without anything. You can add anywhere any number of times. Try some examples for this NFA: YES: b, a, aa, bb, aaa, bbb,.. For example, a = a, so YES. NO: ab, bba, ba, abab,. 10 5
6 DFA Example: NFA for (a b)*abb (from previous slide) Equivalent DFA for (a b)*abb NFA are easier. DFA are difficult. Try some examples for this DFA: YES: aaaabb, ababababb, abb,. NO: a, bb, b, abab,. 11 Write Program for Lexical Analyzer Lexical analyzer itself is a program. Actually, the whole compiler is a program. However, this program must be written in a language that already exists. For example, if you want to write a new programming language D now in year 2016, then its lexical analyzer (and also other parts of the compiler of D) must be written in a language that is available now, such as C, C++, Java, Python, etc. The algorithm for writing the lexical analyzer program is based on the NFA or DFA. The program sans the input program (D language program) and identifies the tokens and put them in symbol table. 12 6
7 Overall Picture of Lexical Analyzer of a Language like C, C++, Java, Identify all possible patterns in the language: letter, digit, number, keywords, arithmetic operators, logical operators, For each of them, write regular expression. For each pattern, construct NFA or DFA. Draw transition diagrams for convenience and as an intermediate step. Combine them in one diagram. Write program for Lexical Analyzer accordingly in an existing different language to identify the tokens. Take input program (C or C++ or Java ) as string. Run the program for Lexical Analyzer and identify the tokens and store them in symbol tables. 13 Example: Overall Picture of Lexical Analyzer of a Language  Suppose that, we want to write a new programming language D. It only has two keywords KSA and 123. We want to write its compiler in C. As a first step, we write only Lexical Analyzer. The two regular expressions are: KSA and 123. Combined regular expression is: KSA 123. NFA: Start Start K 1 S 2 A 3 Combine: Start K 1 S 2 A
8 Example: Overall Picture of Lexical Analyzer of a Language  Suppose that the input D program are stored in the string input.  Following is a sample C code for Lexical Analyzer of D if (input[0] == K ) if (input[1] == S ) if (input[2] == A ) symbol_table[0] = KSA ; else if (input[0] == 1 ) if (input[1] == 2 ) if (input[2] == 3 ) symbol_table[0] = 123 ; Example 1: Example 2: my_program_1.d KSA Symbol Table 0 KSA my_program_2.d KSS Symbol Table Empty 15 8
Dr. D.M. Akbar Hussain
1 2 Compiler Construction F6S Lecture  2 1 3 4 Compiler Construction F6S Lecture  2 2 5 #include.. #include main() { char in; in = getch ( ); if ( isalpha (in) ) in = getch ( ); else error (); while
More informationFormal Languages and Compilers Lecture VI: Lexical Analysis
Formal Languages and Compilers Lecture VI: Lexical Analysis Free University of BozenBolzano Faculty of Computer Science POS Building, Room: 2.03 artale@inf.unibz.it http://www.inf.unibz.it/ artale/ Formal
More informationZhizheng Zhang. Southeast University
Zhizheng Zhang Southeast University 2016/10/5 Lexical Analysis 1 1. The Role of Lexical Analyzer 2016/10/5 Lexical Analysis 2 2016/10/5 Lexical Analysis 3 Example. position = initial + rate * 60 2016/10/5
More informationLexical Analysis. Dragon Book Chapter 3 Formal Languages Regular Expressions Finite Automata Theory Lexical Analysis using Automata
Lexical Analysis Dragon Book Chapter 3 Formal Languages Regular Expressions Finite Automata Theory Lexical Analysis using Automata Phase Ordering of FrontEnds Lexical analysis (lexer) Break input string
More informationUNIT 2 LEXICAL ANALYSIS
OVER VIEW OF LEXICAL ANALYSIS UNIT 2 LEXICAL ANALYSIS o To identify the tokens we need some method of describing the possible tokens that can appear in the input stream. For this purpose we introduce
More informationCompiler Construction
Compiler Construction Exercises 1 Review of some Topics in Formal Languages 1. (a) Prove that two words x, y commute (i.e., satisfy xy = yx) if and only if there exists a word w such that x = w m, y =
More informationConcepts Introduced in Chapter 3. Lexical Analysis. Lexical Analysis Terms. Attributes for Tokens
Concepts Introduced in Chapter 3 Lexical Analysis Regular Expressions (REs) Nondeterministic Finite Automata (NFA) Converting an RE to an NFA Deterministic Finite Automatic (DFA) Lexical Analysis Why separate
More information1. Lexical Analysis Phase
1. Lexical Analysis Phase The purpose of the lexical analyzer is to read the source program, one character at time, and to translate it into a sequence of primitive units called tokens. Keywords, identifiers,
More informationWeek 2: Syntax Specification, Grammars
CS320 Principles of Programming Languages Week 2: Syntax Specification, Grammars Jingke Li Portland State University Fall 2017 PSU CS320 Fall 17 Week 2: Syntax Specification, Grammars 1/ 62 Words and Sentences
More informationLexical Analysis. Sukree Sinthupinyo July Chulalongkorn University
Sukree Sinthupinyo 1 1 Department of Computer Engineering Chulalongkorn University 14 July 2012 Outline Introduction 1 Introduction 2 3 4 Transition Diagrams Learning Objectives Understand definition of
More informationChapter 3: Lexical Analysis
Chapter 3: Lexical Analysis A simple way to build a lexical analyzer is to construct a diagram that illustrates the structure of tokens of the source language, and then to hand translate the diagram into
More informationStructure of Programming Languages Lecture 3
Structure of Programming Languages Lecture 3 CSCI 6636 4536 Spring 2017 CSCI 6636 4536 Lecture 3... 1/25 Spring 2017 1 / 25 Outline 1 Finite Languages Deterministic Finite State Machines Lexical Analysis
More informationCS Lecture 2. The Front End. Lecture 2 Lexical Analysis
CS 1622 Lecture 2 Lexical Analysis CS 1622 Lecture 2 1 Lecture 2 Review of last lecture and finish up overview The first compiler phase: lexical analysis Reading: Chapter 2 in text (by 1/18) CS 1622 Lecture
More information2. λ is a regular expression and denotes the set {λ} 4. If r and s are regular expressions denoting the languages R and S, respectively
Regular expressions: a regular expression is built up out of simpler regular expressions using a set of defining rules. Regular expressions allows us to define tokens of programming languages such as identifiers.
More informationCOMP421 Compiler Design. Presented by Dr Ioanna Dionysiou
COMP421 Compiler Design Presented by Dr Ioanna Dionysiou Administrative! [ALSU03] Chapter 3  Lexical Analysis Sections 3.13.4, 3.63.7! Reading for next time [ALSU03] Chapter 3 Copyright (c) 2010 Ioanna
More informationDixita Kagathara Page 1
2014 Sem  VII Lexical Analysis 1) Role of lexical analysis and its issues. The lexical analyzer is the first phase of compiler. Its main task is to read the input characters and produce as output a sequence
More informationFormal Languages and Compilers Lecture IV: Regular Languages and Finite. Finite Automata
Formal Languages and Compilers Lecture IV: Regular Languages and Finite Automata Free University of BozenBolzano Faculty of Computer Science POS Building, Room: 2.03 artale@inf.unibz.it http://www.inf.unibz.it/
More informationLexical Analysis. Introduction
Lexical Analysis Introduction Copyright 2015, Pedro C. Diniz, all rights reserved. Students enrolled in the Compilers class at the University of Southern California have explicit permission to make copies
More informationCS402 Theory of Automata Solved Subjective From Midterm Papers. MIDTERM SPRING 2012 CS402 Theory of Automata
Solved Subjective From Midterm Papers Dec 07,2012 MC100401285 Moaaz.pk@gmail.com Mc100401285@gmail.com PSMD01 MIDTERM SPRING 2012 Q. Point of Kleen Theory. Answer: (Page 25) 1. If a language can be accepted
More informationLexical Analysis (ASU Ch 3, Fig 3.1)
Lexical Analysis (ASU Ch 3, Fig 3.1) Implementation by hand automatically ((F)Lex) Lex generates a finite automaton recogniser uses regular expressions Tasks remove white space (ws) display source program
More informationAssignment 1 (Lexical Analyzer)
Assignment 1 (Lexical Analyzer) Compiler Construction CS4435 (Spring 2015) University of Lahore Maryam Bashir Assigned: Saturday, March 14, 2015. Due: Monday 23rd March 2015 11:59 PM Lexical analysis Lexical
More informationImplementation of Lexical Analysis
Implementation of Lexical Analysis Outline Specifying lexical structure using regular expressions Finite automata Deterministic Finite Automata (DFAs) Nondeterministic Finite Automata (NFAs) Implementation
More informationCompiler Construction LECTURE # 3
Compiler Construction LECTURE # 3 The Course Course Code: CS4141 Course Title: Compiler Construction Instructor: JAWAD AHMAD Email Address: jawadahmad@uoslahore.edu.pk Web Address: http://csandituoslahore.weebly.com/cc.html
More informationFront End: Lexical Analysis. The Structure of a Compiler
Front End: Lexical Analysis The Structure of a Compiler Constructing a Lexical Analyser By hand: Identify lexemes in input and return tokens Automatically: LexicalAnalyser generator We will learn about
More informationUNIT II LEXICAL ANALYSIS
UNIT II LEXICAL ANALYSIS 2 Marks 1. What are the issues in lexical analysis? Simpler design Compiler efficiency is improved Compiler portability is enhanced. 2. Define patterns/lexeme/tokens? This set
More informationCS 314 Principles of Programming Languages. Lecture 3
CS 314 Principles of Programming Languages Lecture 3 Zheng Zhang Department of Computer Science Rutgers University Wednesday 14 th September, 2016 Zheng Zhang 1 CS@Rutgers University Class Information
More information2. Lexical Analysis! Prof. O. Nierstrasz!
2. Lexical Analysis! Prof. O. Nierstrasz! Thanks to Jens Palsberg and Tony Hosking for their kind permission to reuse and adapt the CS132 and CS502 lecture notes.! http://www.cs.ucla.edu/~palsberg/! http://www.cs.purdue.edu/homes/hosking/!
More informationCS321 Languages and Compiler Design I. Winter 2012 Lecture 4
CS321 Languages and Compiler Design I Winter 2012 Lecture 4 1 LEXICAL ANALYSIS Convert source file characters into token stream. Remove contentfree characters (comments, whitespace,...) Detect lexical
More informationLast lecture CMSC330. This lecture. Finite Automata: States. Finite Automata. Implementing Regular Expressions. Languages. Regular expressions
Last lecture CMSC330 Finite Automata Languages Sets of strings Operations on languages Regular expressions Constants Operators Precedence 1 2 Finite automata States Transitions Examples Types This lecture
More informationLexical Analysis. Lecture 34
Lexical Analysis Lecture 34 Notes by G. Necula, with additions by P. Hilfinger Prof. Hilfinger CS 164 Lecture 34 1 Administrivia I suggest you start looking at Python (see link on class home page). Please
More informationLexical Analysis. Lecture 24
Lexical Analysis Lecture 24 Notes by G. Necula, with additions by P. Hilfinger Prof. Hilfinger CS 164 Lecture 2 1 Administrivia Moving to 60 Evans on Wednesday HW1 available Pyth manual available on line.
More informationCS 314 Principles of Programming Languages
CS 314 Principles of Programming Languages Lecture 2: Syntax Analysis Zheng (Eddy) Zhang Rutgers University January 22, 2018 Announcement First recitation starts this Wednesday Homework 1 will be release
More informationCS415 Compilers. Lexical Analysis
CS415 Compilers Lexical Analysis These slides are based on slides copyrighted by Keith Cooper, Ken Kennedy & Linda Torczon at Rice University Lecture 7 1 Announcements First project and second homework
More informationLexical Analysis  1. A. Overview A.a) Role of Lexical Analyzer
CMPSC 470 Lecture 02 Topics: Regular Expression Transition Diagram Lexical Analyzer Implementation A. Overview A.a) Role of Lexical Analyzer Lexical Analysis  1 Lexical analyzer does: read input character
More informationThe Front End. The purpose of the front end is to deal with the input language. Perform a membership test: code source language?
The Front End Source code Front End IR Back End Machine code Errors The purpose of the front end is to deal with the input language Perform a membership test: code source language? Is the program wellformed
More informationUNIT III. The following section deals with the compilation procedure of any program.
Pune Vidyarthi Griha s COLLEGE OF ENGINEERING, NASHIK4. 1 UNIT III Role of lexical analysis parsing & Token, patterns and Lexemes & Lexical Errors, regular definitions for the language constructs & strings,
More informationImplementation of Lexical Analysis
Implementation of Lexical Analysis Outline Specifying lexical structure using regular expressions Finite automata Deterministic Finite Automata (DFAs) Nondeterministic Finite Automata (NFAs) Implementation
More informationAssignment 1 (Lexical Analyzer)
Assignment 1 (Lexical Analyzer) Compiler Construction CS4435 (Spring 2015) University of Lahore Maryam Bashir Assigned: Saturday, March 14, 2015. Due: Monday 23rd March 2015 11:59 PM Lexical analysis Lexical
More informationLexical Analysis. Chapter 2
Lexical Analysis Chapter 2 1 Outline Informal sketch of lexical analysis Identifies tokens in input string Issues in lexical analysis Lookahead Ambiguities Specifying lexers Regular expressions Examples
More informationLexical Analysis. Lecture 3. January 10, 2018
Lexical Analysis Lecture 3 January 10, 2018 Announcements PA1c due tonight at 11:50pm! Don t forget about PA1, the Cool implementation! Use Monday s lecture, the video guides and Cool examples if you re
More informationLexical Analyzer Scanner
Lexical Analyzer Scanner ASU Textbook Chapter 3.1, 3.3, 3.4, 3.6, 3.7, 3.5 Tsansheng Hsu tshsu@iis.sinica.edu.tw http://www.iis.sinica.edu.tw/~tshsu 1 Main tasks Read the input characters and produce
More informationWe use L i to stand for LL L (i times). It is logical to define L 0 to be { }. The union of languages L and M is given by
The term languages to mean any set of string formed from some specific alphaet. The notation of concatenation can also e applied to languages. If L and M are languages, then L.M is the language consisting
More information2068 (I) Attempt all questions.
2068 (I) 1. What do you mean by compiler? How source program analyzed? Explain in brief. 2. Discuss the role of symbol table in compiler design. 3. Convert the regular expression 0 + (1 + 0)* 00 first
More informationCS 3100 Models of Computation Fall 2011 This assignment is worth 8% of the total points for assignments 100 points total.
CS 3100 Models of Computation Fall 2011 This assignment is worth 8% of the total points for assignments 100 points total September 7, 2011 Assignment 3, Posted on: 9/6 Due: 9/15 Thursday 11:59pm 1. (20
More informationChapter 3 Lexical Analysis
Chapter 3 Lexical Analysis Outline Role of lexical analyzer Specification of tokens Recognition of tokens Lexical analyzer generator Finite automata Design of lexical analyzer generator The role of lexical
More informationCompiler course. Chapter 3 Lexical Analysis
Compiler course Chapter 3 Lexical Analysis 1 A. A. Pourhaji Kazem, Spring 2009 Outline Role of lexical analyzer Specification of tokens Recognition of tokens Lexical analyzer generator Finite automata
More informationCS308 Compiler Principles Lexical Analyzer Li Jiang
CS308 Lexical Analyzer Li Jiang Department of Computer Science and Engineering Shanghai Jiao Tong University Content: Outline Basic concepts: pattern, lexeme, and token. Operations on languages, and regular
More informationCS412/413. Introduction to Compilers Tim Teitelbaum. Lecture 2: Lexical Analysis 23 Jan 08
CS412/413 Introduction to Compilers Tim Teitelbaum Lecture 2: Lexical Analysis 23 Jan 08 Outline Review compiler structure What is lexical analysis? Writing a lexer Specifying tokens: regular expressions
More informationLexical Analyzer Scanner
Lexical Analyzer Scanner ASU Textbook Chapter 3.1, 3.3, 3.4, 3.6, 3.7, 3.5 Tsansheng Hsu tshsu@iis.sinica.edu.tw http://www.iis.sinica.edu.tw/~tshsu 1 Main tasks Read the input characters and produce
More informationfor (i=1; i<=100000; i++) { x = sqrt (y); // square root function cout << x+i << endl; }
Ex: The difference between Compiler and Interpreter The interpreter actually carries out the computations specified in the source program. In other words, the output of a compiler is a program, whereas
More informationInterpreter. Scanner. Parser. Tree Walker. read. request token. send token. send AST I/O. Console
Scanning 1 read Interpreter Scanner request token Parser send token Console I/O send AST Tree Walker 2 Scanner This process is known as: Scanning, lexing (lexical analysis), and tokenizing This is the
More informationAutomata Theory TEST 1 Answers Max points: 156 Grade basis: 150 Median grade: 81%
Automata Theory TEST 1 Answers Max points: 156 Grade basis: 150 Median grade: 81% 1. (2 pts) See text. You can t be sloppy defining terms like this. You must show a bijection between the natural numbers
More informationLexical Analysis. Implementation: Finite Automata
Lexical Analysis Implementation: Finite Automata Outline Specifying lexical structure using regular expressions Finite automata Deterministic Finite Automata (DFAs) Nondeterministic Finite Automata (NFAs)
More informationProf. Mohamed Hamada Software Engineering Lab. The University of Aizu Japan
Compilers Prof. Mohamed Hamada Software Engineering Lab. The University of Aizu Japan Lexical Analyzer (Scanner) 1. Uses Regular Expressions to define tokens 2. Uses Finite Automata to recognize tokens
More informationCT32 COMPUTER NETWORKS DEC 2015
Q.2 a. Using the principle of mathematical induction, prove that (10 (2n1) +1) is divisible by 11 for all n N (8) Let P(n): (10 (2n1) +1) is divisible by 11 For n = 1, the given expression becomes (10
More informationR10 SET a) Construct a DFA that accepts an identifier of a C programming language. b) Differentiate between NFA and DFA?
R1 SET  1 1. a) Construct a DFA that accepts an identifier of a C programming language. b) Differentiate between NFA and DFA? 2. a) Design a DFA that accepts the language over = {, 1} of all strings that
More informationLexical Analysis. COMP 524, Spring 2014 Bryan Ward
Lexical Analysis COMP 524, Spring 2014 Bryan Ward Based in part on slides and notes by J. Erickson, S. Krishnan, B. Brandenburg, S. Olivier, A. Block and others The Big Picture Character Stream Scanner
More information2010: Compilers REVIEW: REGULAR EXPRESSIONS HOW TO USE REGULAR EXPRESSIONS
2010: Compilers Lexical Analysis: Finite State Automata Dr. Licia Capra UCL/CS REVIEW: REGULAR EXPRESSIONS a Character in A Empty string R S Alternation (either R or S) RS Concatenation (R followed by
More informationImplementation of Lexical Analysis
Implementation of Lexical Analysis Lecture 4 (Modified by Professor Vijay Ganesh) Tips on Building Large Systems KISS (Keep It Simple, Stupid!) Don t optimize prematurely Design systems that can be tested
More informationComputer Science Department Carlos III University of Madrid Leganés (Spain) David Griol Barres
Computer Science Department Carlos III University of Madrid Leganés (Spain) David Griol Barres dgriol@inf.uc3m.es Introduction: Definitions Lexical analysis or scanning: To read from lefttoright a source
More informationCPS 506 Comparative Programming Languages. Syntax Specification
CPS 506 Comparative Programming Languages Syntax Specification Compiling Process Steps Program Lexical Analysis Convert characters into a stream of tokens Lexical Analysis Syntactic Analysis Send tokens
More informationG Compiler Construction Lecture 4: Lexical Analysis. Mohamed Zahran (aka Z)
G22.2130001 Compiler Construction Lecture 4: Lexical Analysis Mohamed Zahran (aka Z) mzahran@cs.nyu.edu Role of the Lexical Analyzer Remove comments and white spaces (aka scanning) Macros expansion Read
More informationOutline. 1 Scanning Tokens. 2 Regular Expresssions. 3 Finite State Automata
Outline 1 2 Regular Expresssions Lexical Analysis 3 Finite State Automata 4 Nondeterministic (NFA) Versus Deterministic Finite State Automata (DFA) 5 Regular Expresssions to NFA 6 NFA to DFA 7 8 JavaCC:
More informationLexical analysis. Syntactical analysis. Semantical analysis. Intermediate code generation. Optimization. Code generation. Target specific optimization
Second round: the scanner Lexical analysis Syntactical analysis Semantical analysis Intermediate code generation Optimization Code generation Target specific optimization Lexical analysis (Chapter 3) Why
More informationCSCIGA Compiler Construction Lecture 4: Lexical Analysis I. Hubertus Franke
CSCIGA.2130001 Compiler Construction Lecture 4: Lexical Analysis I Hubertus Franke frankeh@cs.nyu.edu Role of the Lexical Analyzer Remove comments and white spaces (aka scanning) Macros expansion Read
More informationfor (i=1; i<=100000; i++) { x = sqrt (y); // square root function cout << x+i << endl; }
Ex: The difference between Compiler and Interpreter The interpreter actually carries out the computations specified in the source program. In other words, the output of a compiler is a program, whereas
More informationDavid Griol Barres Computer Science Department Carlos III University of Madrid Leganés (Spain)
David Griol Barres dgriol@inf.uc3m.es Computer Science Department Carlos III University of Madrid Leganés (Spain) OUTLINE Introduction: Definitions The role of the Lexical Analyzer Scanner Implementation
More informationLexical Analysis 1 / 52
Lexical Analysis 1 / 52 Outline 1 Scanning Tokens 2 Regular Expresssions 3 Finite State Automata 4 Nondeterministic (NFA) Versus Deterministic Finite State Automata (DFA) 5 Regular Expresssions to NFA
More informationRegular Languages and Regular Expressions
Regular Languages and Regular Expressions According to our definition, a language is regular if there exists a finite state automaton that accepts it. Therefore every regular language can be described
More informationA simple syntaxdirected
Syntaxdirected is a grammaroriented compiling technique Programming languages: Syntax: what its programs look like? Semantic: what its programs mean? 1 A simple syntaxdirected Lexical Syntax Character
More informationCOMPILER DESIGN UNIT I LEXICAL ANALYSIS. Translator: It is a program that translates one language to another Language.
UNIT I LEXICAL ANALYSIS Translator: It is a program that translates one language to another Language. Source Code Translator Target Code 1. INTRODUCTION TO LANGUAGE PROCESSING The Language Processing System
More informationUNIONFREE DECOMPOSITION OF REGULAR LANGUAGES
UNIONFREE DECOMPOSITION OF REGULAR LANGUAGES Thesis submitted in partial fulfillment of the requirements for the award of degree of Master of Engineering in Computer Science and Engineering Submitted
More informationECS 120 Lesson 7 Regular Expressions, Pt. 1
ECS 120 Lesson 7 Regular Expressions, Pt. 1 Oliver Kreylos Friday, April 13th, 2001 1 Outline Thus far, we have been discussing one way to specify a (regular) language: Giving a machine that reads a word
More informationCompiling Regular Expressions COMP360
Compiling Regular Expressions COMP360 Logic is the beginning of wisdom, not the end. Leonard Nimoy Compiler s Purpose The compiler converts the program source code into a form that can be executed by the
More information2.2 Syntax Definition
42 CHAPTER 2. A SIMPLE SYNTAXDIRECTED TRANSLATOR sequence of "threeaddress" instructions; a more complete example appears in Fig. 2.2. This form of intermediate code takes its name from instructions
More informationAnnouncements! P1 part 1 due next Tuesday P1 part 2 due next Friday
Announcements! P1 part 1 due next Tuesday P1 part 2 due next Friday 1 Finitestate machines CS 536 Last time! A compiler is a recognizer of language S (Source) a translator from S to T (Target) a program
More informationMidTerm Papers Solved MCQS with Reference (1 to 22 lectures)
CS606 Compiler Construction MidTerm Papers Solved MCQS with Reference (1 to 22 lectures) by Arslan Arshad (Zain) FEB 21,2016 03002462284 http://lmshelp.blogspot.com/ Arslan.arshad01@gmail.com AKMP01
More informationChapter Seven: Regular Expressions
Chapter Seven: Regular Expressions Regular Expressions We have seen that DFAs and NFAs have equal definitional power. It turns out that regular expressions also have exactly that same definitional power:
More informationCompiler Construction
Compiler Construction Thomas Noll Software Modeling and Verification Group RWTH Aachen University https://moves.rwthaachen.de/teaching/ss16/cc/ Conceptual Structure of a Compiler Source code x1 := y2
More informationTheory and Compiling COMP360
Theory and Compiling COMP360 It has been said that man is a rational animal. All my life I have been searching for evidence which could support this. Bertrand Russell Reading Read sections 2.1 3.2 in the
More informationAutomating Construction of Lexers
Automating Construction of Lexers Regular Expression to Programs Not all regular expressions are simple. How can we write a lexer for (a*b aaa)? Tokenizing aaaab Vs aaaaaa Regular Expression Finite state
More informationCompiler Construction
Compiler Construction Lecture 2: Lexical Analysis I (Introduction) Thomas Noll Lehrstuhl für Informatik 2 (Software Modeling and Verification) noll@cs.rwthaachen.de http://moves.rwthaachen.de/teaching/ss14/cc14/
More informationCSE450. Translation of Programming Languages. Lecture 20: Automata and Regular Expressions
CSE45 Translation of Programming Languages Lecture 2: Automata and Regular Expressions Finite Automata Regular Expression = Specification Finite Automata = Implementation A finite automaton consists of:
More informationRegular Expressions & Automata
Regular Expressions & Automata CMSC 132 Department of Computer Science University of Maryland, College Park Regular expressions Notation Patterns Java support Automata Languages Finite State Machines Turing
More informationIntroduction to Lexical Analysis
Introduction to Lexical Analysis Outline Informal sketch of lexical analysis Identifies tokens in input string Issues in lexical analysis Lookahead Ambiguities Specifying lexical analyzers (lexers) Regular
More informationNondeterministic Finite Automata (NFA)
Nondeterministic Finite Automata (NFA) CAN have transitions on the same input to different states Can include a ε or λ transition (i.e. move to new state without reading input) Often easier to design
More informationGroup A Assignment 3(2)
Group A Assignment 3(2) Att (2) Perm(3) Oral(5) Total(10) Sign Title of Assignment: Lexical analyzer using LEX. 3.1.1 Problem Definition: Lexical analyzer for sample language using LEX. 3.1.2 Perquisite:
More informationCSc 453 Compilers and Systems Software
CSc 453 Compilers and Systems Software 3 : Lexical Analysis I Christian Collberg Department of Computer Science University of Arizona collberg@gmail.com Copyright c 2009 Christian Collberg August 23, 2009
More informationCOMPILER DESIGN LECTURE NOTES
COMPILER DESIGN LECTURE NOTES UNIT 1 1.1 OVERVIEW OF LANGUAGE PROCESSING SYSTEM 1.2 Preprocessor A preprocessor produce input to compilers. They may perform the following functions. 1. Macro processing:
More informationQuestion Bank. 10CS63:Compiler Design
Question Bank 10CS63:Compiler Design 1.Determine whether the following regular expressions define the same language? (ab)* and a*b* 2.List the properties of an operator grammar 3. Is macro processing a
More informationPart 5 Program Analysis Principles and Techniques
1 Part 5 Program Analysis Principles and Techniques Front end 2 source code scanner tokens parser il errors Responsibilities: Recognize legal programs Report errors Produce il Preliminary storage map Shape
More informationA Scanner should create a token stream from the source code. Here are 4 ways to do this:
Writing A Scanner A Scanner should create a token stream from the source code. Here are 4 ways to do this: A. Hack something together till it works. (Blech!) B. Use the language specs to produce a Deterministic
More informationAdministrivia. Lexical Analysis. Lecture 24. Outline. The Structure of a Compiler. Informal sketch of lexical analysis. Issues in lexical analysis
dministrivia Lexical nalysis Lecture 24 Notes by G. Necula, with additions by P. Hilfinger Moving to 6 Evans on Wednesday HW available Pyth manual available on line. Please log into your account and electronically
More informationQUESTIONS RELATED TO UNIT I, II And III
QUESTIONS RELATED TO UNIT I, II And III UNIT I 1. Define the role of input buffer in lexical analysis 2. Write regular expression to generate identifiers give examples. 3. Define the elements of production.
More informationWriting a Lexical Analyzer in Haskell (part II)
Writing a Lexical Analyzer in Haskell (part II) Today Regular languages and lexicographical analysis part II Some of the slides today are from Dr. Saumya Debray and Dr. Christian Colberg This week PA1:
More informationChapter 4. Lexical analysis. Concepts. Lexical scanning Regular expressions DFAs and FSAs Lex. Lexical analysis in perspective
Chapter 4 Lexical analysis Lexical scanning Regular expressions DFAs and FSAs Lex Concepts CMSC 331, Some material 1998 by Addison Wesley Longman, Inc. 1 CMSC 331, Some material 1998 by Addison Wesley
More informationSyntactic Analysis. CS345H: Programming Languages. Lecture 3: Lexical Analysis. Outline. Lexical Analysis. What is a Token? Tokens
Syntactic Analysis CS45H: Programming Languages Lecture : Lexical Analysis Thomas Dillig Main Question: How to give structure to strings Analogy: Understanding an English sentence First, we separate a
More informationCMSC 132: ObjectOriented Programming II
CMSC 132: ObjectOriented Programming II Regular Expressions & Automata Department of Computer Science University of Maryland, College Park 1 Regular expressions Notation Patterns Java support Automata
More informationG52LAC Languages and Computation Lecture 6
G52LAC Languages and Computation Lecture 6 Equivalence of Regular Expression and Finite Automata Henrik Nilsson University of Nottingham G52LACLanguages and ComputationLecture 6 p.1/28 This Lecture (1)
More informationDVA337 HT17  LECTURE 4. Languages and regular expressions
DVA337 HT17  LECTURE 4 Languages and regular expressions 1 SO FAR 2 TODAY Formal definition of languages in terms of strings Operations on strings and languages Definition of regular expressions Meaning
More information