Xtext: Difference between production and datatype rule

1
votes

Can someone explain to me the difference between a production and datatype rule in xtext? I know so far that both are parser rules and Datatype Rule returns a primitive EDataype and production rule creates an EObject in the AST.. But I can't see a differnce in their grammar definition:

Dataype Rule: Decimal: INT '.' INT ;

Producion Rule: Model: (stats += Statement)* ;

How did the parser know which is what rule?

1
parsingxtext

1 Answers

4
votes

The parser uses the (inferred) return type of the parser rule to distinguish between productions and data types. If the returned type is an EMF EDataType, the rule is a data type rule, otherwise it's a production rule.

This blog entry tries to highlight some differences between the kinds of rules in Xtext.