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Assignments and function output have same sintax [message #985883]

Fri, 16 November 2012 09:51

Eclipse User

I've got a situation that can be summarized with this little code:

Instruction:
   EmptyInstruction | Assignment;

EmptyInstruction: ';';

Assignment:
   variable=[Variable]':='expression=Expression';' ;

Function:
   'FUNCTION' name=ID
   instructions+=Instruction*
   output=[Function]':='expression=Expression';' ;

I know where is the problem, but how can I resolve the non-LL decision?

Very thank you for help.

[Updated on: Fri, 16 November 2012 09:52] by Moderator

Re: Assignments and function output have same sintax [message #986163 is a reply to message #985883]

Mon, 19 November 2012 04:22

Eclipse User

I see no problem with this (Xtext 2.3.1). Enhanced with some more rules it works for me:

Grammar:

Model:
	(functions += Function)*;
	
Instruction:
   EmptyInstruction | Assignment;

EmptyInstruction: {EmptyInstruction} ';';

Assignment:
   variable=[Variable]':='expression=Expression';' ;

Function:
   'FUNCTION' name=ID
   vars += Variable*
   instructions+=Instruction*
   output=[Function]':='expression=Expression';' ;

Variable: name=ID ';';
Expression: value=INT | var=[Variable];

DSL:

FUNCTION a
  b;
  c;
  b := 1;
  c := b;
  a := c;

Re: Assignments and function output have same sintax [message #986254 is a reply to message #986163]

Mon, 19 November 2012 11:22

Eclipse User

I solve with option

backtrack=true

UPDATE:
Problem comes out also in this situation:

RealValue:
INT '.' INT;

Array:
name=ID 'ARRAY' '[' initial=INT '..' final=INT ']' ';';

When, in my DSL, I try to write something like this:

v ARRAY [1..10];

I'll receive an error: after the '.' it wants an INT.

Very thank you!

[Updated on: Mon, 19 November 2012 11:43] by Moderator

Re: Assignments and function output have same sintax [message #986265 is a reply to message #986254]

Mon, 19 November 2012 11:41

Eclipse User

Problem comes out also in this situation:

RealValue:
INT '.' INT;

Array:
name=ID 'ARRAY' '[' initial=INT '..' final=INT ']' ';';

When, in my DSL, I try to write something like this:

v ARRAY [1..10];

I'll receive an error: after the '.' it wants an INT.

Very thank you!

Re: Assignments and function output have same sintax [message #986266 is a reply to message #986254]

Mon, 19 November 2012 11:41

Eclipse User

Problem comes out also in this situation:

RealValue:
INT '.' INT;

Array:
name=ID 'ARRAY' '[' initial=INT '..' final=INT ']' ';';

When, in my DSL, I try to write something like this:

v ARRAY [1..10];

I'll receive an error: after the '.' it wants an INT.

Very thank you!

Re: Assignments and function output have same sintax [message #986325 is a reply to message #986266]

Mon, 19 November 2012 19:36

Eclipse User

backtrack=true

is strongly discouraged. It suspends all those warnings, so you have no idea, something else is broken too.
Besides that, you have no control, which way the parse will take ignoring the warning. Consider using syntactic predicated '=>' instead.

Re: Assignments and function output have same sintax [message #986358 is a reply to message #986325]

Tue, 20 November 2012 03:47

Eclipse User

Boris Brodski wrote on Tue, 20 November 2012 01:36

backtrack=true
is strongly discouraged. It suspends all those warnings, so you have no idea, something else is broken too.
Besides that, you have no control, which way the parse will take ignoring the warning. Consider using syntactic predicated '=>' instead.

Very thank you for suggest, I was able to disable the backtrack. For the moment it works fine.

Now I'm going to finish the grammar,
thanks!

Re: Assignments and function output have same sintax [message #986612 is a reply to message #985883]

Wed, 21 November 2012 03:19

Eclipse User

Maybe solved.

[Updated on: Thu, 22 November 2012 04:58] by Moderator

Re: Assignments and function output have same sintax [message #987212 is a reply to message #986612]

Sat, 24 November 2012 09:27

Eclipse User

Ciao Tommaso

as they already told you, stay away from backtrack=true :)

you can find an example expression language here

http://xsemantics.sourceforge.net/xsemantics-documentation/Expressions-example.html#Expressions

hope this helps
Lorenzo

On 11/21/2012 09:19 AM, Tommaso De Sica wrote:
> Similar problem that I can't solve:
>
>
> Expression:
> (expression=NumericExpression) | (expression=BoolExpr)
> ;
>
> BoolExpr returns BoolExpr:
> OrExpr;
>
> OrExpr returns BoolExpr:
> AndExpr ({Or.left=current} 'OR' right=AndExpr)*;
>
> AndExpr returns BoolExpr:
> PrimaryExpr ({And.left=current} 'AND' right=PrimaryExpr)*;
>
> PrimaryExpr returns BoolExpr:
> '(' BoolExpr ')' | BoolLiteral;
>
> BoolLiteral:
> ...
> ;
>
> NumericExpression returns IntegerExpression:
> Multiplication ({NumericExpression.left=current} ('+'|'-')
> right=Multiplication)*;
>
> Multiplication returns IntegerExpression:
> Pow ({Multiplication.left=current} ('*'|'/'|'MOD') right=Pow)*;
>
> Pow returns IntegerExpression:
> Primary ({Pow.left=current} '**' right=Primary)*;
>
> Primary returns IntegerExpression:
> NumberLiteral |
> '(' NumericExpression ')' |
> '-'NumberLiteral;
>
> NumberLiteral:
> ...;
>
> error is the same, but I can't understand how use => in this case.
> Someone can halp me? Very thank you!

--
Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino
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Re: Assignments and function output have same sintax [message #987389 is a reply to message #987212]

Mon, 26 November 2012 07:05

Eclipse User

Yes, I was able to rewrite the grammar unambiguous.
backtrack=true is just a memory Confused

Thanks for replies!

Re: Assignments and function output have same sintax [message #987390 is a reply to message #987389]

Mon, 26 November 2012 07:17

Eclipse User

Very well (y)

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