| cons | System Class |
A cons is a compound object having two components, called the car and cdr. These form a dotted pair. Each component can be any object.
Specializing.
| (cons [car-typespec [cdr-typespec]]) |
car-typespec — a type specifier, or the symbol *. The default is the symbol *.
cdr-typespec — a type specifier, or the symbol *. The default is the symbol *.
This denotes the set of conses whose car is constrained to be of type car-typespec and whose cdr is constrained to be of type cdr-typespec. (If either car-typespec or cdr-typespec is *, it is as if the type t had been denoted.)
Section 2.4.1 (Left-Parenthesis), Section 22.1.3.5 (Printing Lists and Conses)