2.6 Locations: #%variable-reference
|(#%variable-reference (#%top . id))|
Produces an opaque variable reference value representing the location of id, which must be bound as a top-level variable or module-level variable. If no id is supplied, the resulting value refers to an “anonymous” variable defined within the enclosing context (i.e., within the enclosing module, or at the top level if the form is not inside a module).
A variable reference can be used with variable-reference->empty-namespace, variable-reference->resolved-module-path, and variable-reference->top-level-namespace, but facilities like define-namespace-anchor and namespace-anchor->namespace wrap those to provide an clearer interface. A variable reference is also useful to low-level extensions; see Inside: PLT Scheme C API.