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Class precedence list:
parse-tree, standard-object, slot-object, tThe base class for all parse trees.
We use the term parse tree in a wider sense than what is common in the parsing literature, in that a lexeme is a (trivial) parse tree. The parser does not distinguish between lexemes and other parse trees, and a grammar rule can produce a lexeme if that should be desired.
The offset in the buffer of the first character of a parse tree.
The offset in the buffer of the character following the last one of a parse tree.
The length of a parse-tree is thus the difference of its end offset and its start offset.
The start offset and the end offset may be NIL which is typically the case when a parse tree is derived from the empty sequence of lexemes.