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Using variables with predefined functions [message #899409]

Tue, 31 July 2012 17:48

Charalampos Alexopoulos

Messages: 13
Registered: July 2012

Junior Member

Hi

I am creating the grammar for the OpenSCAD (www.openscad.org). A valid snippet of the OpenSCAD code is:

a=-13;
b=a*2;
c=2*abs(a);
a=(b/c)*6;

I start from the arithmetics example and implement most of the aspects of the language, but i have some problems. Here is a simplified version of my grammar which relate to my problems:

Code:

(imports+=Import)*
(statements+=Statement)*;

Import:
'include<' importedNamespace=ImportName '>';

ImportName:
ID ('.' 'scad')?;

Statement:
ModuleDeclaration | Command;

Command:
Variable | ModuleCall ;

Predefined:
ABS | SQRT
;

SQRT:
'sqrt'
;

ABS:
'abs'
;

AbstractDefinition:
DeclaredParameter | Variable | Function ;

ModuleDeclaration:
'module' name=ID '(' (args+=DeclaredParameter (',' args+=DeclaredParameter)*)? ')' '{' command+=Command*'}';

ModuleCall:
method = [ModuleDeclaration] '(' (args+=DeclaredParameter (',' args+=DeclaredParameter)*)? ')' ';'
;

DeclaredParameter:
name=ID ('=' ('+' | '-')? parameters=Expression)?;

Function:
name=Predefined '(' ('+' | '-')? parameters=Expression ')';

Variable:
name=ID '=' ('+' | '-')? expression=Expression ';';

Expression:
Addition;

Addition returns Expression:
Multiplication (({Plus.left=current} '+' | {Minus.left=current} '-') right=Multiplication)*;

Multiplication returns Expression:
PrimaryExpression (({Multi.left=current} '*' | {Div.left=current} '/') right=PrimaryExpression)*;

PrimaryExpression returns Expression:
'(' Expression ')' | {NumberLiteral} value=NUMBER
| {FunctionCall} func=[AbstractDefinition] ('(' args+=Expression (',' args+=Expression)* ')')?;

terminal NUMBER returns ecore::EBigDecimal:
('0'..'9')* ('.' ('0'..'9')+)?;

terminal INT returns ecore::EInt:
'this one has been deactivated';

It generate the code and run with no errors or warnings, but i have two problems in the sample code. In the predefined function 'abs ' i get the message "no viable alternative at input 'abs' and in the definitions of variable 'a' i get the message "duplicate statement 'a'". The language aloud duplicate definition of variable.

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Re: Using variables with predefined functions [message #899466 is a reply to message #899409]

Wed, 01 August 2012 02:52

Henrik Lindberg

Messages: 2509
Registered: July 2009

Senior Member

Have not looked in detail, but I suspect there is a problem with
references - remember that something like func= [AbstractDefinition]
really means func = [AbstractDefinition | ID ] - which means "parse and
ID and use that to reference an instance of AbstractDefinition with
matching name.

So... your functions 'abs' and 'sqr' are declared as keywords, and the
lexer will not produce an ID token for these.

You can try something like:

FUNCID = 'abs' | 'sqr' | ID ;
and reference with
func = [AbstractDefinition|FUNCID]

Hope that helps.
- henrik

On 2012-31-07 19:48, Charalampos Alexopoulos wrote:
> Hi
>
> I am creating the grammar for the OpenSCAD (www.openscad.org). A valid
> snippet of the OpenSCAD code is:
>
> a=-13;
> b=a*2;
> c=2*abs(a);
> a=(b/c)*6;
>
> I start from the arithmetics example and implement most of the aspects
> of the language, but i have some problems. Here is a simplified version
> of my grammar which relate to my problems:
>
> Code:
>
> (imports+=Import)* (statements+=Statement)*;
>
> Import:
> 'include<' importedNamespace=ImportName '>';
>
> ImportName:
> ID ('.' 'scad')?;
>
> Statement:
> ModuleDeclaration | Command;
>
> Command:
> Variable | ModuleCall ;
>
> Predefined:
> ABS | SQRT
> ;
>
> SQRT:
> 'sqrt'
> ;
>
>
> ABS:
> 'abs'
> ;
>
>
>
>
> AbstractDefinition:
> DeclaredParameter | Variable | Function ;
>
> ModuleDeclaration:
> 'module' name=ID '(' (args+=DeclaredParameter (','
> args+=DeclaredParameter)*)? ')' '{' command+=Command*'}';
>
> ModuleCall:
> method = [ModuleDeclaration] '(' (args+=DeclaredParameter (','
> args+=DeclaredParameter)*)? ')' ';'
> ;
>
> DeclaredParameter:
> name=ID ('=' ('+' | '-')? parameters=Expression)?;
>
> Function:
> name=Predefined '(' ('+' | '-')? parameters=Expression ')';
>
> Variable:
> name=ID '=' ('+' | '-')? expression=Expression ';';
>
> Expression:
> Addition;
>
> Addition returns Expression:
> Multiplication (({Plus.left=current} '+' | {Minus.left=current}
> '-') right=Multiplication)*;
>
> Multiplication returns Expression:
> PrimaryExpression (({Multi.left=current} '*' | {Div.left=current}
> '/') right=PrimaryExpression)*;
>
> PrimaryExpression returns Expression:
> '(' Expression ')' | {NumberLiteral} value=NUMBER
> | {FunctionCall} func=[AbstractDefinition] ('('
> args+=Expression (',' args+=Expression)* ')')?;
>
> terminal NUMBER returns ecore::EBigDecimal:
> ('0'..'9')* ('.' ('0'..'9')+)?;
>
> terminal INT returns ecore::EInt:
> 'this one has been deactivated';
>
>
> It generate the code and run with no errors or warnings, but i have two
> problems in the sample code. In the predefined function 'abs ' i get the
> message "no viable alternative at input 'abs' and in the definitions of
> variable 'a' i get the message "duplicate statement 'a'". The language
> aloud duplicate definition of variable.

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Re: Using variables with predefined functions (Solved) [message #900051 is a reply to message #899466]

Fri, 03 August 2012 16:48

Charalampos Alexopoulos

Messages: 13
Registered: July 2012

Junior Member

Thank you for the explanation.
Your suggestion didn't work but help me to improve my poor understanding of the Xtext.
I put a solution to my problem in case somebody helped by this.
First of all my approach was completely wrong, even when i make it to work it produce a wrong behavior. So the solution was to immediate add the Function to PrimaryExpression with 'syntactic predicate'.

PrimaryExpression returns Expression:
'(' Expression ')' | {NumberLiteral} value=NUMBER
| => Function
| {FunctionCall} func=[AbstractDefinition ] ('(' args+=Expression (',' args+=Expression)* ')')?;

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