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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