1 Symbol Tables. 2 Contents Introduction Introduction A Simple Compiler A Simple Compiler Scanning – Theory and Practice Scanning – Theory and Practice.

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Symbol TablesSymbol Tables

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ContentsContents IntroductionIntroduction A Simple CompilerA Simple Compiler Scanning – Theory and PracticeScanning – Theory and Practice Grammars and ParsingGrammars and Parsing LL(1) ParsingLL(1) Parsing Lex and yaccLex and yacc LR ParsingLR Parsing Semantic ProcessingSemantic Processing Symbol TablesSymbol Tables Run-time Storage OrganizationRun-time Storage Organization Code Generation and Local Code OptimizationCode Generation and Local Code Optimization Global OptimizationGlobal Optimization

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A Symbol Table InterfaceA Symbol Table Interface

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A Symbol Table Interface A Symbol Table Interface (cont’d.)(cont’d.)

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A Symbol Table Interface A Symbol Table Interface (cont’d.)(cont’d.)

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Basic Implementation TechniquesBasic Implementation Techniques Unordered ListUnordered List Ordered ListOrdered List Binary Search TreesBinary Search Trees

The expected search time is O(log(n))The expected search time is O(log(n)) For a balanced tree, the worst-case performance is For a balanced tree, the worst-case performance is

O(n).O(n).

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Basic Implementation Techniques Basic Implementation Techniques (cont’d.)(cont’d.)

Hash TablesHash Tables Hash functionHash function

Resolving collisionsResolving collisions LinearLinear

If position h(n) is occupied, try (h(n)+1) mod mIf position h(n) is occupied, try (h(n)+1) mod m Add-the-hash rehashAdd-the-hash rehash

If position h(n) is occupied, try (2*h(n)) mod mIf position h(n) is occupied, try (2*h(n)) mod m Quadratic rehashQuadratic rehash

If position h(n) is If position h(n) is occupied, try (h(n)+1**2) occupied, try (h(n)+1**2) mod mmod m

Collision resolution by Collision resolution by chainingchaining

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Basic Implementation Techniques Basic Implementation Techniques (cont’d.)(cont’d.)

String Space ArraysString Space Arrays A fixed-size arrayA fixed-size array

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Basic Implementation Techniques Basic Implementation Techniques (cont’d.)(cont’d.)

Segmented String Space ArraysSegmented String Space Arrays A dynamic-allocation arrayA dynamic-allocation array

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Block-Structured Symbol TablesBlock-Structured Symbol Tables

Block structured languagesBlock structured languages

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Block-Structured Symbol Tables Block-Structured Symbol Tables (cont’d.)(cont’d.)

Visibility rulesVisibility rules

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Block-Structured Symbol Tables Block-Structured Symbol Tables (cont’d.)(cont’d.)

An Individual Table for Each ScopeAn Individual Table for Each Scope

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Block-Structured Symbol Tables Block-Structured Symbol Tables (cont’d.)(cont’d.)

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Block-Structured Symbol Tables Block-Structured Symbol Tables (cont’d.)(cont’d.)

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Block-Structured Symbol Tables Block-Structured Symbol Tables (cont’d.)(cont’d.)

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