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Rule has non-LL(*) decision even tho its copied from a lecture [message #1811127]

Tue, 27 August 2019 09:05

Jakob Sachs

Messages: 15
Registered: May 2018

Junior Member

Hi
I need to parse Expressions in my DSL and copied the grammar pretty much exactly from here: http://dsl-course.org/

But when I parse it I get two errors:

Quote:

InternalXtextTest.g:6065:3: [fatal] rule ruleOr has non-LL(*) decision due to recursive rule invocations reachable from alts 1,2. Resolve by left-factoring or using syntactic predicates or using backtrack=true option.

InternalXtextTest.g:6131:3: [fatal] rule ruleAnd has non-LL(*) decision due to recursive rule invocations reachable from alts 1,2. Resolve by left-factoring or using syntactic predicates or using backtrack=true option.

I'm really confused why this is happening since my version is practically 1 to 1 what is used everywhere else.

Heres my code for the expressions:

Expression:
	Or;

Or returns Expression:
	And ({Or.left=current} ('OR' | 'or') right=And)*;

And returns Expression:
	Equality ({And.left=current} ('AND' | 'and') right=Equality)*;

Equality returns Expression:
	Comparison ({Equality.left=current} ('!=' | '==') right=Comparison)*;

Comparison returns Expression:
	PlusOrMinus ({Comparison.left=current} ('>=' | '<=' | '<' | '>') right=PlusOrMinus)*;

PlusOrMinus returns Expression:
	MultiOrDivide ({PlusOrMinus.left=current} ('+' | '-') right=MultiOrDivide)*;

MultiOrDivide returns Expression:
	Primary ({MultiOrDivide.left=current} ('*' | '/') right=Primary)*;

Primary returns Expression:
	'(' Expression ')' | '!' expression=Primary | '-' expression=Primary | Atomic;

Atomic returns Expression:
	{Expression} DOUBLE | {Expression} INT | {Expression} STRING | var=[VariableName];

Update:
I found out that it has to do with my VariableName definition. If I exclude that part of the expression that says " | var=[VariableName]" it works fine.
This confuses me even more.
This is my code for VariableAssignments:

  
VariableAssignment:
	name=VariableName '=' value=Expression ';';

VariableName:
	name=(ID | TERMINAL_CONSTANT);

[Updated on: Tue, 27 August 2019 09:11]

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1811128 is a reply to message #1811127]

Tue, 27 August 2019 09:27

Tamas Miklossy

Messages: 157
Registered: February 2016

Senior Member

Hello Jakob,

a nice introduction to expression languages in Xtext is available under https://youtu.be/d3JymwcB_TM

Maybe it helps you further.

Tamás

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1811132 is a reply to message #1811128]

Tue, 27 August 2019 10:06

Jakob Sachs

Messages: 15
Registered: May 2018

Junior Member

Thanks, tho I already watched that twice.. :/

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1811137 is a reply to message #1811132]

Tue, 27 August 2019 11:59

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

can you please provide a complete grammar. for me it looks more like a problem with double.

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1811144 is a reply to message #1811137]

Tue, 27 August 2019 13:26

Jakob Sachs

Messages: 15
Registered: May 2018

Junior Member

Uhm I don't think to post my whole grammar is gonna help much cause its 750 lines.. and most of it is string literal constants.

So I'm gonna post the actual "logic" of my grammar without all the constants.

grammar com.me.XtextTest with org.eclipse.xtext.common.Terminals

generate xtextTest 'http://www.me.com/XtextTest'

Model:
	statements+=Statement*;

terminal DOUBLE:
	('0'..'9')+ '.' ('0'..'9')*;

terminal COMMENT:
	'#' !('\n' | '\r')* ('\r'? '\n')?;

terminal LiteralBoolean:
	'true' | 'false' | 'TRUE' | 'FALSE';


Statement:
	{Statement} ('RETURN' | 'return') ';' |
	VariableAssignment |
	IfStatement |
	('PRINT' | 'print') '(' Expression ')' ';' |
	('print_reset' | 'PRINT_RESET') ';'
	("setaddressbook"|"SETADDRESSBOOK") '(' Expression (',' exps+=Expression ',' exps+=Expression ','
	exps+=Expression)? ')' ';' ;

IfStatement:
	('if' | 'IF') '(' condition=Expression ')' '{' statements+=Statement* '}' (=> 'else' (('if' | 'IF') '('
	else_condition=Expression ')')? '{'
	elseStatements+=Statement* '}')*;

VariableAssignment:
	name=VariableName '=' value=Expression ';';

VariableName:
	name=ID ;

Expression:
	Or;

Or returns Expression:
	And ({Or.left=current} ('OR' | 'or') right=And)*;

And returns Expression:
	Equality ({And.left=current} ('AND' | 'and') right=Equality)*;

Equality returns Expression:
	Comparison ({Equality.left=current} ('!=' | '==') right=Comparison)*;

Comparison returns Expression:
	PlusOrMinus ({Comparison.left=current} ('>=' | '<=' | '<' | '>') right=PlusOrMinus)*;

PlusOrMinus returns Expression:
	MultiOrDivide ({PlusOrMinus.left=current} ('+' | '-') right=MultiOrDivide)*;

MultiOrDivide returns Expression:
	Primary ({MultiOrDivide.left=current} ('*' | '/') right=Primary)*;

Primary returns Expression:
	'(' Expression ')' | '!' expression=Primary | '-' expression=Primary | Atomic;

Atomic returns Expression:
	{VarRef} var=[VariableName] | {Expression} DOUBLE | {Expression} INT | {Expression} STRING
	| ('strlen' | 'STRLEN') '(' Expression ')'
	| ('trim' | 'TRIM') '(' exps+=Expression (',' exps+=Expression (',' exps+=Expression (',' TrimKeyword)?)?)? ')';

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1811145 is a reply to message #1811144]

Tue, 27 August 2019 13:36

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

this is still incomplete and generates fine with an improvised

TrimKeyword:
'TRIM'
;

=> please try to create a really minified grammar that actually has the problem.
otherwise i cannot / wont help

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1811146 is a reply to message #1811145]

Tue, 27 August 2019 13:47

Jakob Sachs

Messages: 15
Registered: May 2018

Junior Member

Huh okay, I'm sorry.
I'll try to get the smallest version which shows the problem.

Thanks for the help sofar

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1814041 is a reply to message #1811146]

Mon, 02 September 2019 09:49

Jakob Sachs

Messages: 15
Registered: May 2018

Junior Member

Okay, I found the smallest Version of my grammar that still produces the error::

grammar com.me.XtextTest with org.eclipse.xtext.common.Terminals

import "http://www.eclipse.org/emf/2002/Ecore" as ecore
generate xtextTest 'http://www.me.com/XtextTest'

Model:
	statements+=Statement*;

terminal DOUBLE:
	('0'..'9')+ '.' ('0'..'9')*;

@Override
terminal INT returns ecore::EInt:
	('0'..'9')+;
terminal COMMENT:
	'#' !('\n' | '\r')* ('\r'? '\n')?;
terminal LiteralBoolean:
	'true' | 'false' | 'TRUE' | 'FALSE'; OR_KEYWORD:
	'OR' | 'or';

AND_KEYWORD:
	'AND' | 'and';

COMPARISON_OPERATOR:
	'==' | '<=' | '>=' | '!=' | '<' | '>';

Statement:
	{Statement} ('RETURN' | 'return') ';' |
	VariableAssignment |
	SelectTableEntry;

SelectTableEntry:
	('selecttableentry' | 'SELECTTABLEENTRY') ('from' | 'FROM') tableName=ID ('WITH' | 'with')
	'(' selCond=GeneralSelectionCondition ')';

GeneralSelectionCondition:
	'!' GeneralSelectionCondition | '(' GeneralSelectionCondition ')' | GeneralSelectionComposition
	({GeneralSelectionCondition.left=current} op=(OR_KEYWORD | AND_KEYWORD) right=GeneralSelectionComposition)*;

GeneralSelectionComposition:
	tableFieldName=GeneralTableFieldName op=(COMPARISON_OPERATOR | 'LIKE' | 'like' | '!LIKE' | '!like') expr=Expression;

GeneralTableFieldName:
	ID;

VariableAssignment:
	name=VariableName '=' value=Expression ';';

VariableName:
	name=(ID);

Expression:
	Or;

Or returns Expression:
	And ({Or.left=current} OR_KEYWORD right=And)*;

And returns Expression:
	Equality ({And.left=current} AND_KEYWORD right=Equality)*;

Equality returns Expression:
	Comparison ({Equality.left=current} ('!=' | '==') right=Comparison)*;

Comparison returns Expression:
	PlusOrMinus ({Comparison.left=current} ('>=' | '<=' | '<' | '>') right=PlusOrMinus)*;

PlusOrMinus returns Expression:
	MultiOrDivide ({PlusOrMinus.left=current} ('+' | '-') right=MultiOrDivide)*;

MultiOrDivide returns Expression:
	Primary ({MultiOrDivide.left=current} ('*' | '/') right=Primary)*;

Primary returns Expression:
	'(' Expression ')' | '!' expression=Primary | '-' expression=Primary | Atomic;

Atomic returns Expression:
	{VarRef} var=[VariableName] | {Expression} DOUBLE | {Expression} INT | {Expression} STRING';

It is definitely related to the rule: GeneralFieldName

I couldn't find out how to fix this tho.

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1814051 is a reply to message #1814041]

Mon, 02 September 2019 10:24

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

here is a much more minified version of the grammar

Model:
	statements+=SelectTableEntry;
	
OR_KEYWORD:
	'OR' | 'or';


COMPARISON_OPERATOR:
	'==' | '<=' | '>=' | '!=' | '<' | '>';

SelectTableEntry:
	
	'(' selCond=GeneralSelectionCondition ')';

GeneralSelectionCondition:
	'!' GeneralSelectionCondition
	({GeneralSelectionCondition.left=current} op=(OR_KEYWORD ) right=GeneralSelectionComposition)*;

GeneralSelectionComposition:
	tableFieldName=ID op=(COMPARISON_OPERATOR) expr=Expression;

Expression:
	Or;

Or returns Expression:
	Comparison ({Or.left=current} OR_KEYWORD right=Comparison)*;

Comparison returns Expression:
	Primary ({Comparison.left=current} ('>=' | '<=' | '<' | '>') right=Primary)*;

Primary returns Expression:
	'!' expression=Primary | Atomic;

Atomic returns Expression:
	{VarRef} var=ID;

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

[Updated on: Mon, 02 September 2019 10:27]

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1814053 is a reply to message #1814051]

Mon, 02 September 2019 10:38

Jakob Sachs

Messages: 15
Registered: May 2018

Junior Member

Thanks, yeah true this is even smaller and still generates the Error.

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Re: Rule has non-LL(*) decision even tho its copied from a lecture [message #1814054 is a reply to message #1814053]

Mon, 02 September 2019 10:45

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

you might use predicates => to help the parser if the OR belongs to inner our outer like

Or returns Expression:
Comparison =>({Or.left=current} OR_KEYWORD right=Comparison)*;

GeneralSelectionCondition:
'!' GeneralSelectionCondition
=>({GeneralSelectionCondition.left=current} op=(OR_KEYWORD ) right=GeneralSelectionCompositio

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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