Home » Modeling » TMF (Xtext) » HOW DO YOU MODEL A DECIMAL? (I can't find a good way to construct a DECIMAL rule.)
HOW DO YOU MODEL A DECIMAL? [message #915322] 
Mon, 17 September 2012 03:48 
JJ Mising name Messages: 12 Registered: November 2010 
Junior Member 


I can't seem to find a way to model a decimal. These rules nearly work and I understand that there is an ambiguity with INT, but I am trying to create a decimal rule that would allow things like 0.1, 12, 23.234235 ...
terminal INT returns ecore::EInt:('0'..'9')  (('1'..'9') ('0'..'9')+ ) ;
DECIMAL returns ecore::EString : ''? INT ('.' INT)? ;
POSINTNUMBER returns ecore::EString : INT ;
NEGINTNUMBER returns ecore::EString : '' INT ;
INTNUMBER:
POSINTNUMBER  NEGINTNUMBER ;
Again I understand that my DECIMAL rule can evaluate to INT in the case of say '12', but it actually works. I do get the right value. The only time these rules don't work is when the value starts with '0' for instance 0.1 creates an error. I resulted in making sure INT would allow a single digit (see INT rule above), but that didn't change anything.
Could someone tell me what I am missing? Again, everything works perfectly except the case 0.XXX '12' and '23.234234' work just fine, negatives too, POSINT and NETINT work well.
thanks,
JJ



Re: HOW DO YOU MODEL A DECIMAL? [message #915368 is a reply to message #915322] 
Mon, 17 September 2012 06:35 
Ed Willink Messages: 4600 Registered: July 2009 
Senior Member 


Hi
If you're happy to model decimal as EString rather than EBigDecimal you
might just model aNumber and let the ValueConverters sort out the details.
Alternatively having INT return EString can give you more flexibility
over reuse again letting ValueConverters sort out the details.
[For OCL, where there are further ambiguities for e.g. "4..9" as a range
and "x.y" as a model navigation, the EssentialOCL grammar lies and
declares that a decimal is parsed as an INT, but actually a customized
TokenSource acts as a prelexer so that numeric '.' sequences appear to
Xtext as atomic tokens avoiding the need for clever disambiguation in
the subsequent rules.]
Regards
Ed Willink
On 17/09/2012 04:48, JJ Mising name wrote:
> I can't seem to find a way to model a decimal. These rules nearly work
> and I understand that there is an ambiguity with INT, but I am trying
> to create a decimal rule that would allow things like 0.1, 12,
> 23.234235 ...
>
>
> terminal INT returns ecore::EInt:('0'..'9')  (('1'..'9') ('0'..'9')+ ) ;
>
> DECIMAL returns ecore::EString : ''? INT ('.' INT)? ;
>
> POSINTNUMBER returns ecore::EString : INT ;
>
> NEGINTNUMBER returns ecore::EString : '' INT ;
>
> INTNUMBER:
> POSINTNUMBER  NEGINTNUMBER ;
>
> Again I understand that my DECIMAL rule can evaluate to INT in the
> case of say '12', but it actually works. I do get the right value. The
> only time these rules don't work is when the value starts with '0' for
> instance 0.1 creates an error. I resulted in making sure INT would
> allow a single digit (see INT rule above), but that didn't change
> anything.
> Could someone tell me what I am missing? Again, everything works
> perfectly except the case 0.XXX '12' and '23.234234' work just fine,
> negatives too, POSINT and NETINT work well.
> thanks,
>
> JJ



Re: HOW DO YOU MODEL A DECIMAL? [message #915453 is a reply to message #915322] 
Mon, 17 September 2012 10:02 
Henrik Lindberg Messages: 2509 Registered: July 2009 
Senior Member 


I use:
terminal INT : ('0'..'9')+;
REAL hidden(): INT ? '.' (EXT_INT  INT);
terminal EXT_INT: INT ('e''E')('''+') INT;
Note that REAL is not a terminal.
I also don't associate value converters with these as there are other
places where I need INT, REAL etc as strings. So I also have:
RealValue returns ecore::EDoubleObject: REAL ;
Hope that helps.
Regards
 henrik
On 20121709 5:48, JJ Mising name wrote:
> I can't seem to find a way to model a decimal. These rules nearly work
> and I understand that there is an ambiguity with INT, but I am trying to
> create a decimal rule that would allow things like 0.1, 12, 23.234235 ...
>
>
> terminal INT returns ecore::EInt:('0'..'9')  (('1'..'9') ('0'..'9')+ ) ;
>
> DECIMAL returns ecore::EString : ''? INT ('.' INT)? ;
>
> POSINTNUMBER returns ecore::EString : INT ;
>
> NEGINTNUMBER returns ecore::EString : '' INT ;
>
> INTNUMBER:
> POSINTNUMBER  NEGINTNUMBER ;
>
> Again I understand that my DECIMAL rule can evaluate to INT in the case
> of say '12', but it actually works. I do get the right value. The only
> time these rules don't work is when the value starts with '0' for
> instance 0.1 creates an error. I resulted in making sure INT would allow
> a single digit (see INT rule above), but that didn't change anything.
> Could someone tell me what I am missing? Again, everything works
> perfectly except the case 0.XXX '12' and '23.234234' work just fine,
> negatives too, POSINT and NETINT work well.
> thanks,
>
> JJ


 
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