Most objects have more than one possible textual representation. For example, the positive integer with a magnitude of twenty-seven can be textually expressed in any of these ways:
27 27. #o33 #x1B #b11011 #.(* 3 3 3) 81/3
A list containing the two symbols A and B can also be textually
expressed in a variety of ways:
(A B) (a b) ( a b ) (\A |B|)
(|\A|
B
)
In general, from the point of view of the Lisp reader, wherever whitespace is permissible in a textual representation, any number of spaces and newlines can appear in standard syntax.
When a function such as print produces a printed representation, it must choose from among many possible textual representations. In most cases, it chooses a program readable representation, but in certain cases it might use a more compact notation that is not program-readable.
A number of option variables, called printer control variables , are provided to permit control of individual aspects of the printed representation of objects. Figure 22–1 shows the standardized printer control variables; there might also be implementation-defined printer control variables.
In addition to the printer control variables, the following additional defined names relate to or affect the behavior of the Lisp printer:
| *package* | *read-eval* | readtable-case |
| *read-default-float-format* | *readtable* |