Lexical analyzer

CS40106 Compiler Design Compiler Design 40106

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Course Outline ,[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],Compiler Design 40106

COMPILERS ,[object Object],[object Object],[object Object],Compiler Design 40106 ( Normally a program written in a high-level programming language) ( Normally the equivalent program in machine code – relocatable object file)

Other Applications ,[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Major Parts of Compilers ,[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Phases of A Compiler Compiler Design 40106 Lexical Analyzer Semantic Analyzer Syntax Analyzer Intermediate Code Generator Code Optimizer Code Generator Target Program Source Program ,[object Object],[object Object],[object Object]

1. Lexical Analyzer ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

2. Syntax Analyzer ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106 ,[object Object],[object Object],[object Object]

Syntax Analyzer (CFG) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Syntax Analyzer versus Lexical Analyzer ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Parsing Techniques ,[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],Compiler Design 40106

3. Semantic Analyzer ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

4. Intermediate Code Generation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Intermediate Code Generation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

5. Code Optimizer (for Intermediate Code Generator) ,[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

6. Code Generator ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Phases of compiler Compiler Design 40106

The Structure of a Compiler (8) Scanner [Lexical Analyzer] Parser [Syntax Analyzer] Semantic Process [Semantic analyzer] Code Generator [Intermediate Code Generator] Code Optimizer Parse tree Abstract Syntax Tree w/ Attributes Non-optimized Intermediate Code Optimized Intermediate Code Code Genrator Target machine code Compiler Design 40106 Tokens

The input program as you see it. main () { int i,sum; sum = 0; for (i=1; i<=10; i++); sum = sum + i; printf("%d",sum); } Compiler Design 40106

Introducing Basic Terminology ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Introducing Basic Terminology Compiler Design 40106 Token Sample Lexemes Informal Description of Pattern const if relation id num literal const if <, <=, =, < >, >, >= pi, count , D2 3.1416, 0, 6.02E23 “ core dumped” const if < or <= or = or < > or >= or > letter followed by letters and digits any numeric constant any characters between “ and “ except “ Classifies Pattern ,[object Object],[object Object],[object Object],[object Object]

Attributes for Tokens Tokens influence parsing decision; the attributes influence the translation of tokens. Example: E = M * C ** 2 <id, pointer to symbol-table entry for E> <assign_op, > <id, pointer to symbol-table entry for M> <mult_op, > <id, pointer to symbol-table entry for C> <exp_op, > <num, integer value 2> Compiler Design 40106

Role of the Lexical Analyzer Compiler Design 40106

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Compiler Design 40106

Lexical analyzer

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