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Topic 3: Parsing and Yaccing
COS 320
Compiling Techniques
Princeton University Spring 2015
Prof. David August
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Syntactical Analysis
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Syntactical Analysis
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Context-Free Grammar
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Definitions
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Context-Free Grammar
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Context-Free Grammars
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Start Symbol
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Example
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Example: Leftmost Derivation
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Example: Rightmost Derivation
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Parse Trees
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Ambiguous Grammars
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Ambiguous Grammars
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Ambiguous Grammars
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End-Of-File Marker
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Grammars and Lexical Analysis
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Context-Free Grammars and REs
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Context Free Grammars and REs
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Context-Free Grammar with no RE/FA
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Further Exploration
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Parsing
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Outline
• Recursive Descent Parsing • Shift-Reduce Parsing • ML-Yacc • Recursive Descent Parser Generation
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Recursive Descent Parsing
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Example
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Another Example
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The Problem
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Another Option: Shift-Reduce Parsing
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Shift-Reduce Parsing
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Example
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Example
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Example
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Example
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Example
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The Dangling Else Problem
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ML-YACC (Yet Another Compiler-Compiler)
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Context-Free Grammar Specification
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ML-YACC Declarations
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Attribute Grammar
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Rules
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Example
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ML-YACC and Ambiguous Grammars
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ML-YACC and Ambigous Grammars
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Directives
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Directives
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Precedence Examples
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Default Behavior
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Direct Rule Precedence Specification
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Syntax vs. Semantics
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Recursive Descent/Predictive/LL(1) Parser Generation
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Problem
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Formal Techniques
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Computation of First
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Computation of Follow
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Building a Predictive Parser
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Building a Predictive Parser
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Predictive Parsing Table
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Predictive Parsing Table
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Example
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Example
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Predictive Parsing Table
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Problems
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Problems
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Example
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Example
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Example
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Outline
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Shift-Reduce, Bottom Up, LR(1) Parsing
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LR(k)
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Shift Reduce Parsing DFA
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Parsing Algorithm
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LR(0) Parsing
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LR(0) States
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DFA Table Entry Computation
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Transition Table
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Using The Transition Table
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Another Example
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Another Example - SLR
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Another Example – SLR
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Yet Another Example
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LR(1) Parsing
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Yet Another Example – LR(1)
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Yet Another Example – LR(1)
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LALR(1)
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LALR(1)
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Parsing Power
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Parsing Error Recovery
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Error Recovery
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LL Local Error Recovery
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LL Local Error Recovery
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LR Local Error Recovery
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Global Error Recovery
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Burke-Fisher
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Burke-Fisher
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Burke-Fisher Example
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Burke-Fisher
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Burke-Fisher in ML-YACC
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