'Derivation tree' diaporamas de présentation

Pumping Lemma for Context-free Languages

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COMPILER

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C O N T E X T - F R E E LANGUAGES ( use a grammar to describe a language)

C O N T E X T - F R E E LANGUAGES ( use a grammar to describe a language). Context-free grammars. Ch.1 introduced two different, though equivalent, methods of describing languages: finite automata and regular expressions .

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Chapter 7: Controlling Search

Chapter 7: Controlling Search. Where we discuss how to make the search for a solution more efficient. Controlling Search. Estimating Efficiency of a CLP Program Rule Ordering Literal Ordering Adding Redundant Constraints Minimization Identifying Deterministic Subgoals

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Chapter 5 Context-free Languages

Chapter 5 Context-free Languages. Context-free Grammars. Definition 5.1: A grammar G = (V, T, S, P) is said to be context-free if all production rules in P have the form A ? x where A ? V and x ? (V ? T)*

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Chapter 5 Context-Free Grammars

Chapter 5 Context-Free Grammars. Grammar (Review). A grammar is a 4-tuple G = ( NT , T , P , S ), where NT : a finite set of non-terminal symbols T : a finite set of terminal (alphabet) symbols S : is the starting symbol S ? NT P : a finite set of production rules: x ? y

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Formal Issues in Natural Language Generation

Formal Issues in Natural Language Generation. Lecture 5 Stone, Doran,Webber, Bleam & Palmer. GRE and surface realization. Arguably, GRE uses a grammar. Parameters such as the preference order on properties reflect knowledge of how to communicate effectively.

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Chapter 2. Design of a Simple Compiler

Chapter 2. Design of a Simple Compiler. J. H. Wang Sep. 20, 2011. Outline. An Informal Definition of the ac Language Formal Definition of ac Phases of a Simple compiler Scanning Parsing Abstract Syntax Trees Semantic Analysis Code Generation. Introduction.

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Tutoring and Help Systems

Tutoring and Help Systems. Tell me and I forget. Show me and I remember. Involve me and I understand. - Chinese proverb. Previous Approach. Used for over 20 years Computer-based training (CBT) Computer aided instruction (CAI)

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Chapter 4:Constraint Logic Programs

Chapter 4:Constraint Logic Programs. Where we learn about the only programming concept (rules), and how programs execute. Constraint Logic Programs. User-Defined Constraints Programming with Rules Evaluation Derivation Trees and Finite Failure Goal Evaluation Simplified Derivation Trees

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Context Free Languages

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Languages & Grammars

Languages & Grammars. Languages. FORMAL languages, not natural languages (not even machine languages) Alphabet is all symbols allowed. ? is alphabet, ? is null letter String variables: w = abba Concatenation, reverse, length ? * is 0 or more letters, ? + is 1 or more letters.

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SYNTAX

SYNTAX. Syntax: form, structure The syntax of a pl: The set of its well-formed programs The rules that define these programs Two views: Concrete syntax : program as text Abstract syntax : program as composite structure, a tree. Concrete syntax.

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CSI 3104 /Winter 2006 : Introduction to Formal Languages Chapter 13: Grammatical Format

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Context-free Grammars

Context-free Grammars. Recursive definition Grammar Derivation. What is the syntax of the description (meta-language)? External form of the grammar How do we associate a language with such a description? Semantics or use of the grammar

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PARSING

PARSING. Lecture # 14 Naveen Z Quazilbash. Overview. Parsing Simple grammars-if time permits Reading assignment Quiz no.2. Parsing. Given a string w and a grammar, determine whether the grammar generates w. Finding a derivation of w is called Parsing. E.g. S ?aSb|bSa|SS | ?

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The Cocke-Kasami-Younger Algorithm

The Cocke-Kasami-Younger Algorithm. An example of a CFG in CNF. An example of bottom-up parsing, for CFG in Chomsky normal form. G : S ? AB | BB A ? CC | AB | a B ? BB | CA | b C ? BA | AA | b. 2 possibilities for first production. S. S. S. B. B. A. A. B. A.

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Syntax Analysis

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Context Free Grammar Ambiguity

Context Free Grammar Ambiguity. Brandon McKune April 21, 2012. Context Free Grammar. A context-free grammar (CFG) is a 4-tuple G = (V, ?, S, P) where V and ? are disjoint finite sets, S P is a finite set of formulas of the form A ? , where A ? V and ? (V U ?)*.

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CFG Ambiguity

A CFL is ambiguous for 3 reasons. If G is a CFG, then for any x E L ( G ) these three statements are equivalent: 1. x has more than one derivation tree. 2. x has more than one LMD. 3. x has more than one RMD. CFG Ambiguity. Show the CFG with THE FOLLOWING PRODUCTION AMBIGUOUS.

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