Rewrite class

 

The syntax of a rewrite class declaration is as follows:

Rewrite_Class_Decl	::=	rewrite class Id  ( TypeExp, ¼ , TypeExp )
		[ : Inherit_List ] [ :: Rewrite_Mode ¼ Rewrite_Mode ]
		{ Class_Body } ;
Rewrite_Mode	::=	treeparser
	|	applicative
	|	topdown

This is simply the usual C++ class declaration syntax extended to the following information:

a traversal list

enclosed in parenthesis. The traversal list of a rewrite class defines the set of types that rewriting should traverse. If a datatype object contains an argument of a type not listed in the traversal list, its value will not be altered.

rewrite mode

this defines the rewriting mode of the rewrite class.