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Changing XBase syntax [message #731490]

Sat, 01 October 2011 11:52

Jos Warmer

Messages: 114
Registered: October 2010

Senior Member

Hi,

I am using Xbase as the basis for a expression language for business users. Because of that I want to change the syntax more towards what they are used to. For example, I changed:

if( a == 1 )
    "1"
else 
    "2"

into

IF a > 1 THEN
    "1"
ELSE 
    "2"
ENDIF

This is straightforward.
Then I changed the '==' with the keyword 'EQUALS', expecting it to work in the same straightforward way. To my surprise this doesn't work, I get the error message:

Couldn't resolve reference to JvmIdentifiableElement 'EQUALS'.

It seems that Xbase uses the concrete syntax '==' for the lookup as a Java element. I was not expecting that anything in the concrete syntax would implicitly be part of the abstract syntax of Xbase.

I think Xbase should make this distinction between the abstract and concrete syntax because it makes for a much more clean language definition . That way anyone can simply change the '==' to the 'EQUALS' string and change the concrete syntax to look like what is usual in the domain of the DSL that is being developed. After all, that is what DSL's are about. I think Xbase will appeal to a much larger audience this way.

Given the fact that I cannot do this now, can anyone give a pointer as to what I should do to replace strings like '==' by 'EQUALS' ? I am guessing I should create a ValueConverter and simply change the concrete syntax string to '==' again in there myself.

Jos

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Re: Changing XBase syntax [message #731493 is a reply to message #731490]

Sat, 01 October 2011 11:56

Christian Dietrich

Messages: 14669
Registered: July 2009

Senior Member

Hi,

have a look at the class org.eclipse.xtext.xbase.scoping.featurecalls.OperatorMapping

~Christian

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

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Re: Changing XBase syntax [message #731498 is a reply to message #731493]

Sat, 01 October 2011 12:40

Jos Warmer

Messages: 114
Registered: October 2010

Senior Member

Christian,

The workaround with the ValueConverter works ok, I just tried that out. The OperatorMapping class can be changed to allow for the alternative syntax as well I see. I just need to find out where to inject the new version of the class.

Jos

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