If a grammar contains the production:
expression
->
expression operator expression
with a semantic representation of a list of the individual semantic values, the Lisp grammar would contain the rule:
((
expression expression operator expression
) (list $1 $2 $3))
Error productions of the form:
((
nt
:error) (
some error behavior
))
are explained in the section below.
The first rule of the grammar should be of the form:
((
nt
nt1) $1)
where the non-terminal
nt
has no other productions and
nt1
serves as the main "top-level" non-terminal.