15.3.1.1 The rib object type

Object Type: rib

Disjoint object type representing lexical contours in the expansion process. rib objects associate the source name of syntactic bindings to their label gensyms.

Objects of type rib have the following fields:

name*

List of symbols representing the source name of syntactic bindings. When the rib is sealed: the list is converted to a vector.

mark**

List of sublists of marks; there is a sublist of marks for every item in name*. When the rib is sealed: the list is converted to a vector.

label*

List of label gensyms uniquely identifying syntactic bindings; there is a label for each item in name*. When the rib is sealed: the list is converted to a vector.

sealed/freq

#f or vector of exact integers. When #f: this rib is extensible: new syntactic bindings can be added to it. When a vector: this rib is sealed. See below for an explanation of the frequency vector.