itemization(
    itt($$ = ) 

    A value is assigned to the rule's nonterminal's semantic value. If the
rule's nonterminal was associated with one of the union's field types, then
the matching union field receives the value of the assignment expression's
right-hand side. If no association was defined then the variable representing
the nonterminal's semantic value is a plain union (i.e., tt(STYPE_))
variable.

    itt($$(expr))

    tt(Expr's) value is assigned to the rule's nonterminal's plain union
(i.e., tt(STYPE_)) type. Any association that may have been defined between
the nonterminal and a union field is ignored.

    itt(_$$)

    This refers to the rule's nonterminal's plain union (i.e., tt(STYPE_))
type. Any association that may have been defined between the nonterminal and a
union field is ignored.

    itt($$)

    This refers to the rule's nonterminal's semantic value. If it was
associated with one of the union's types, then tt($$) refers to the associated
union field. If no association was defined then tt($$) represents a plain
union (i.e., tt(STYPE_)) type of variable.

    itt($$.)

    If the rule's nonterminal's semantic value was associated with one of the
union's types, then tt($$.) is shorthand for the member selector operator,
applied to the associated union field type. If no association was defined then
tt($$.) is shorthand for the field selector operator, applied to the
nonterminal's semantic value's plain union (i.e., tt(STYPE_)) type.

    itt($$->)

    If the rule's nonterminal's semantic value was associated with one of the
union's types, then tt($$->) is shorthand for the pointer to member operator,
applied to the associated union field type. If no association was defined then
an error message is issued, as the pointer to member operator is not defined
for plain union types.


    itt(_$1)

    This refers to the current production rule's first component's plain 
union (tt(STYPE_)) value.

    itt($1)

    This shorthand refers to the semantic value of the production rule's
first element. If it was associated with one of the union's types, then tt($1)
refers to the associated union field. If no association was defined then
tt($1) represents a plain union (i.e., tt(STYPE_)) type of variable.

    itt($1.)

    If the production rule's first component's semantic value was associated
with one of the union's types, then tt($1.) is shorthand for the member
selector operator, applied to the associated union field type. If no
association was defined then tt($1.) is shorthand for the field selector
operator, applied to the first component's semantic value's plain union (i.e.,
tt(STYPE_)) type.

    itt($1->)

    If the production rule's first component's semantic value was associated
with one of the union's types, then tt($1->) is shorthand for the pointer to
member operator, applied to the associated union field type. If no association
was defined then an error message is issued, as the pointer to member operator
is not defined for plain union types.


    itt(_$-1)

    This refers to the plain union (tt(STYPE_)) value of a component in a
production rule, listed immediately before the current rule's nonterminal ($-2
refers to a component used two elements before the current nonterminal, etc.).

    itt($-1)

    Same: this refers to the plain union (tt(STYPE_)) value of a component in
a production rule, listed immediately before the current rule's nonterminal
($-2 refers to a component used two elements before the current nonterminal,
etc.).
 
    itt($-1.)

    This is shorthand for the field selector operator applied to to the plain
union (tt(STYPE_)) value of some production rule element, 1 element before
the current rule's nonterminal.

    itt($-1->)

    This shorthand refers to tho pointer to member operator applied to the
plain union (tt(STYPE_)) value of some production rule element, 1 element
before the current rule's nonterminal. Its use results in an error message, as
the pointer to member operator is not defined for plain union types.

    itt($<field>-1)

    This refers to the tt(field) union field of a component in a production
rule, listed immediately before the current rule's nonterminal. Note that the
validity of the specified field for that particular component cannot be
verified by bic().

    itt($<field>-1.)

    This refers to the member selector operator of the tt(field) union field
of a component in a production rule, listed immediately before the current
rule's nonterminal. Note that the validity of the specified field for that
particular component cannot be verified by bic().
 
    itt($<field>-1->)
    This refers to the pointer to member operator of the tt(field) union field
of a component in a production rule, listed immediately before the current
rule's nonterminal. Note that the validity of the specified field for that
particular component cannot be verified by bic().
    )
