ast_sub_tree(?Language, ?ArgumentName) is nondet
name arg2 refers to a subtree of the respective AST node.
For instance, in the Java AST arguments named ''ref'' are references.:
ast_sub_tree('Java', expr). ast_sub_tree('Java', args).
exprargument used above in the definition of
the child expression that represents the message receiver and the
denotes the list of identities of the expressions representing message arguments. * The ''ast_sub_tree/2'' declarations allow language-independent top down traversal of an AST. Language independent bottom up traversals are supported by the convention that the second argument of every AST node has the name ''parent'' and refers to the parent node.