Chapter Two(1)

COMPILER CONSTRUCTION Principles and Practice Kenneth C. Louden

2. Scanning (Lexical Analysis) PART ONE

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Function of a Scanner ,[object Object],[object Object],[object Object],[object Object],[object Object]

The Categories of Tokens ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Relationship between Tokens and its String ,[object Object],[object Object],[object Object]

Relationship between Tokens and its String ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Some Practical Issues of the Scanner ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Some Practical Issues of the Scanner ,[object Object],[object Object],[object Object],[object Object],RET 2 + 4 = ] x e d n i [ a 2 + 4 = ] x e d n i [ a

Some Relative Basic Concepts ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Some Relative Basic Concepts ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

More About Regular Expression ,[object Object],[object Object],[object Object]

2.2.1 Definition of Regular Expressions

Basic Regular Expressions ,[object Object],[object Object],[object Object],[object Object]

Regular Expression Operations ,[object Object],[object Object],[object Object]

Choice Among Alternatives ,[object Object],[object Object],[object Object],[object Object]

Concatenation ,[object Object],[object Object],[object Object],[object Object]

Repetition ,[object Object],[object Object],[object Object]

Precedence of Operation and Use of Parentheses ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Name for regular expression ,[object Object],[object Object],[object Object],[object Object]

Definition of Regular Expression ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Examples of Regular Expressions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Examples of Regular Expressions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Examples of Regular Expressions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Examples of Regular Expressions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],BACK

2.2.2 Extensions to Regular Expression

List of New Operations ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

List of New Operations ,[object Object],[object Object],[object Object],[object Object],[object Object],BACK

2.2.3 Regular Expressions for Programming Language Tokens

Number, Reserved word and Identifiers ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Comments ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Ambiguity ,[object Object],[object Object],[object Object]

White Space and Lookahead ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],RET

Introduction to Finite Automata ,[object Object],[object Object],[object Object],letter 1 letter digit 2

Introduction to Finite Automata ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],letter 1 letter digit 2

More About Finite Automata ,[object Object],[object Object],[object Object]

2.3.1 Definition of Deterministic Finite Automata

The Concept of DFA ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Concept of DFA ,[object Object],[object Object],[object Object],[object Object],[object Object]

Some differences between definition of DFA and the diagram: ,[object Object],[object Object],[object Object],[object Object],[object Object],letter start letter digit In-id

Examples of DFA ,[object Object],[object Object],b Not b Not b not b b not b

Examples of DFA ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],digit digit digit digit +  digit digit

Examples of DFA ,[object Object],[object Object],[object Object],[object Object],[object Object],+ digit digit digit . digit E + － digit digit E －

Examples of DFA ,[object Object],[object Object],BACK * 1 2 3 4 other other / * * / 5

2.3.2 Lookahead, Backtracking, and Nondeterministic Automata

A Typical Action of DFA Algorithm ,[object Object],[object Object],[object Object],start letter finish letter in_id digit [other] return ID

Finite automation for an identifier with delimiter and return value ,[object Object],[object Object],start letter finish letter in_id digit [other] return ID

Finite automation for an identifier with delimiter and return value ,[object Object],[object Object],start letter finish letter in_id digit [other] return ID letter start letter digit In-id

How to arrive at the start state in the first place (combine all the tokens into one DFA)

Each of these tokens begins with a different character ,[object Object],[object Object],[object Object],: < = = = return ASSIGN return LE return EQ : < = = = return ASSIGN return LE return EQ

Several tokens beginning with the same character ,[object Object],[object Object],< < = > < return NE return LT return LE < = > [other] return NE return LT return LE

Expand the Definition of a Finite Automaton ,[object Object],[object Object],[object Object],[object Object]

ε-transition ,[object Object],[object Object],[object Object],

ε-Transitions Used in Two Ways. ,[object Object],[object Object],[object Object],  : <  = = = 

Definition of NFA ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Some Notes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Some Notes ,[object Object],[object Object]

Examples of NFAs ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1 3 2 4 a b a   a b b b

Examples of NFAs ,[object Object],[object Object],[object Object],[object Object],BACK 1 2 3 5    4 6 a c 7   8  9  b 10 

2.3.3 Implementation of Finite Automata in Code

Ways to Translate a DFA or NFA into Code ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1 letter letter 2 digit [other] 3

Ways to Translate a DFA or NFA into Code ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],* 1 2 3 4 other other / * * / 5

Ways to Translate a DFA or NFA into Code ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1 letter letter 2 digit [other] 3

Ways to Translate a DFA or NFA into Code ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],* * 1 2 3 4 5 / * / other other

Ways to Translate a DFA or NFA into Code ,[object Object],[object Object],[object Object],Characters in the alphabet c States representing transitions T (s, c) States s

Ways to Translate a DFA or NFA into Code ,[object Object],[object Object],Brackets indicate “noninput-consuming” transitions This column indicates accepting states yes 3 no [3] 2 2 2 No 2 1 Accepting other digit letter Input char state

Ways to translate a DFA or NFA into Code ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],yes 5 no 3 4 5 4 no 3 4 3 3 no 3 2 no 2 1 Accepting Other * / Input char state

Features of Table-Driven Method ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],RET

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Chapter Two(1)