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How xtext Lexer and Parser works? [message #892816]

Fri, 29 June 2012 20:56

Andrew A

Messages: 9
Registered: June 2012

Junior Member

Hello!

Where can I find the information, how xtext Lexer and Parser works?

I have wrote some xtext grammars, but I still don't understand, what's under the hood.

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Re: How xtext Lexer and Parser works? [message #892845 is a reply to message #892816]

Sat, 30 June 2012 11:32

Christian Dietrich

Messages: 13373
Registered: July 2009

Senior Member

Hi,

ANTLR is under the hood

so let us take the sample grammar

Model:
	greetings+=Greeting*;
	
Greeting:
	'Hello' name=ID '!';

and the sample file

Hello Me!
Hello You!

the lexer divides the file into a token stream

Keyword:"Hello" ID Keyword:"!"
Keyword:"Hello" ID Keyword:"!"

and the parser then assembles the ast based on the rules in the grammar

-Model
--Greeting(name=Me)
--Greeting(name=You)

Maybe some basic reading on formal languages and parsing helps

~Christian

Need professional support for Xtext, Xpand, EMF?
Go to: https://www.itemis.com/en/xtext/
Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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