SYNTAX ANALYSIS

CONTENTS

o Syntax

o Syntax Terminology

o Syntatic element of the Language

o Syntax Analysis

o Formal Methods of Describing Syntax

Grammar

Parts of Grammars

Parse Tree

Syntax Diagram

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Syntax

“The arrangement of words as elements in a sentence to show their relationship” describes the sequence of symbols that make up valid programs.

Form of expressions, statements and program units.

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Syntax Terminology A sentence is a string of characters over some alphabet

A language is a set of sentences

A lexeme is the lowest level syntactic unit of a language (e.g., *, sum, begin)

A token is a category of lexemes (e.g., identifier)

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Syntactic elements of the Language

Keywords and reserved words – is an identifier used as a fixed part of the syntax of a statement. It is a reserved word if it may not be used as a programmer-chosen identifier.

Noise words – optional words that are inserted in a statements to improved readability.

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Syntactic elements of the Language

Comments – important part of the documentation. REM, /* */, or //

Blank (spaces)

Delimiters – a syntactic element used simply to mark the beginning or end of some syntactic unit such as a statement or expression. “begin”…”end”, or { }.

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Syntactic Analysis

Determines if the program being compiled is a valid sentence in the syntactic model programming language.

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Formal Methods of Describing Syntax

Grammars

Parse Trees

Syntax Diagrams

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Grammars

Formal definition of the syntax of a programming language.

Collection of rules that define, mathematically, which strings of symbols are valid sentences.

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Parts of Grammar

Set of tokens/terminal symbols

symbols that are atomic / non-divisible

can be combined to form valid constructs in the language

Set of non-terminal symbols

symbols used to represent intermediate definitions within the language

defined by productions

syntactic classes or categories

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Parse Tree

Parse trees are trees level by symbols of a particular context free grammar(CFG).

Leaves : level by a terminal.

Interior nodes: level by a variable.

Root: must be level by the start symbol.

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Thank you…

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