A lot of prduction classes

["Mattias Grönlund" <mattiasgronlund@hotmail.com>]

Hi,

I have been playing around with the java grammars for ANTLR and SableCC for 
a week and have come up with some questions.

In ANTLR I am able to control the creation of the AST a lot (at the cost of 
more coding), but it feels like I have missed something with SableCC. I get 
a feeling that there is a lot of redundant nodes/classes in the SableCC 
generated AST’s.

As an example take the import_declaration part of the j11.sablecc:

goal = import_declaration;
import_declaration =
    {single_type_import_declaration} single_type_import_declaration |
    {type_import_on_demand_declaration} single_import_on_demand_declaration;

single_type_import_declaration = import name semicolon;

type_import_on_demand_declaration = import name dot star semicolon;

The code will generate the following production classes:
AGoal :: PGoal.java
ASingleTypeImportDeclaration :: PSingleTypeImportDeclaration
ASingleTypeImportDeclarationImportDeclaration :: PImportDeclaration
ATypeImportOnDemandDeclaration :: PTypeImportOnDemandDeclaration
ATypeImportOnDemandDeclarationImportDeclaration :: PImportDeclaration

I can understand the need for production classes, but I do not understand 
what I (miss)understand as the duplication of them.

For all import statements the parser will generate a tree rooted with an 
ASingleTypeImportDeclaration or an 
ATypeImportOnDemandDeclarationImportDeclaration. They in there turn always 
included an ASingleTypeImportDeclaration or an 
ATypedImportOnDemandDeclaration respectively.

I can see the usage of the ASingleTypeImportDeclarationImportDeclaration and 
typedImportOnDemandDeclaration as they share the same superclass, so that 
the can be identified as the same type.

I can also see the usage of the AsingleTypeImportDeclaration and the 
AsingleTypeImportDeclaration as they hold the part that makes the 
production.

Why can’t each of these pars of classes/nodes be consolidated into only one?

/Mattias




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