15.3 The lexical environment

The lexical environment is a compound data structure with the purpose of associating syntactic identifiers to label gensyms and label gensyms to syntactic binding descriptors. The components are:

Lexical context rib objects

Objects of type rib that map syntactic identifiers to label gensyms, keeping track of lexical contours.

Primitive syntactic binding’s labels

A set of label gensyms associated to the syntactic bindings established by the boot image; each label references its syntactic binding’s descriptor.

Imported syntactic binding’s labels

A set of label gensyms associated to the syntactic bindings established by imported libraries; each label references its syntactic binding’s descriptor. The boot image’s syntactic bindings are a subset of the imported syntactic bindings.

Internal syntactic binding’s labels, LEXENV

A set of label gensyms associated to the syntactic bindings established by the library being expanded; these labels are used as keys in an association list mapping labels to their syntactic binding’s descriptor. This alist is called LEXENV.