The final delimiter of an interactive stream:

This final delimiter is never actually seen by programs; no need to test for #\^D or #\^Z - use READ-CHAR-NO-HANG to check for end-of-stream.

A newline character can be entered by the user by pressing the Enter key.

See also Section 21.13, “Function CLEAR-INPUT”.

Safety settings are ignored by the interpreted code; therefore where the standard uses the phrase “should signal an error”, an ERROR is SIGNALed. See Section 3.3.5, “Declaration SAFETY” for the safety of compiled code.

All 978 symbols in the “COMMON-LISP” package specified by the [ANSI CL standard] are implemented.

The standard characters are #\Newline and the graphic characters with a CODE-CHAR between 32 and 126 (inclusive).

The requirement of step 4 that a “reader macro function may return zero values or one value” is enforced. You can use the function VALUES to control the number of values returned.

A reserved token , i.e., a token that has potential number syntax but cannot be interpreted as a NUMBER, is interpreted as SYMBOL when being read.

When a token with package markers is read, then no checking is done whether the SYMBOL-PACKAGE part and the SYMBOL-NAME part do not have number syntax. (What would the purpose of this check be?) So we consider tokens like USER:: or :1 or LISP::4711 or 21:3 as symbols.

The backquote read macro also works when nested. Example:

   (EVAL ``(,#'(LAMBDA () ',a) ,#'(LAMBDA () ',b)))
 ≡ (EVAL `(list #'(LAMBDA () ',a) #'(LAMBDA () ',b)))
 ≡ (EVAL (list 'list (list 'function (list 'lambda nil (list 'quote a)))
                     (list 'function (list 'lambda nil (list 'quote b)))))

Reader macros are also defined for the following:

The CLOS symbols are EXPORTed from the package “CLOS”. “COMMON-LISP” uses (as in USE-PACKAGE) “CLOS” and EXT:RE-EXPORTs the [ANSI CL standard] standard exported symbols (the CLISP extensions, e.g., those described in Chapter 29, Meta-Object Protocol, are not EXT:RE-EXPORTed). Since the default :USE argument to MAKE-PACKAGE is “COMMON-LISP”, the standard CLOS symbols are normally visible in all user-defined packages. If you do not want them (for example, if you want to use the PCL implementation of CLOS instead of the native one), do the following:

(DEFPACKAGE "CL-NO-CLOS" (:use "CL"))
(DO-EXTERNAL-SYMBOLS (symbol “COMMON-LISP”)
  (SHADOW symbol "CL-NO-CLOS"))
(DO-SYMBOLS (symbol "CL-NO-CLOS")
  (EXPORT symbol "CL-NO-CLOS"))
(IN-PACKAGE "CL-NO-CLOS")
(LOAD "pcl")	; or whatever
(DEFPACKAGE "MY-USER" (:use "CL-NO-CLOS"))
(IN-PACKAGE "MY-USER")
;; your code which uses PCL goes here

DEFCLASS supports the option :METACLASS STRUCTURE-CLASS. This option is necessary in order to define a subclass of a DEFSTRUCT-defined structure type using DEFCLASS instead of DEFSTRUCT.

When CALL-NEXT-METHOD is called with arguments, the rule that the ordered set of applicable methods must be the same as for the original arguments is enforced by the implementation only in interpreted code.

CLOS:GENERIC-FLET and CLOS:GENERIC-LABELS are implemented as macros, not as special operators (as permitted by [sec_3-1-2-1-2-2]). They are not imported into the packages “COMMON-LISP-USER” and “COMMON-LISP” because of the [ANSI CL standard] issue GENERIC-FLET-POORLY-DESIGNED:DELETE.

PRINT-OBJECT is only called on objects of type STANDARD-OBJECT and STRUCTURE-OBJECT. It is not called on other objects, like CONSes and NUMBERs, due to the performance concerns.

Among those classes listed in Figure 4-8, only the following are instances of BUILT-IN-CLASS:

DEFCLASS supports the :METACLASS option. Possible values are STANDARD-CLASS (the default), STRUCTURE-CLASS (which creates structure classes, like DEFSTRUCT does), and user-defined meta-classes (see Section 29.3.6.7, “Generic Function CLOS:VALIDATE-SUPERCLASS”).

It is not required that the superclasses of a class are defined before the DEFCLASS form for the class is evaluated. Use Meta-Object Protocol generic functions CLOS:CLASS-FINALIZED-P to check whether the class has been finalized and thus its instances can be created, and CLOS:FINALIZE-INHERITANCE to force class finalization.

See also Section 29.3.1, “Macro DEFCLASS”.

Trivial changes, e.g., those that can occur when doubly loading the same code, do not require updating the instances. These are the changes that do not modify the set of local slots accessible in instances, e.g., changes to slot options :INITFORM, :DOCUMENTATION, and changes to class options :DEFAULT-INITARGS, :DOCUMENTATION.

The instances are updated when they are first accessed, not at the time when the class is redefined or MAKE-INSTANCES-OBSOLETE is called. When the class has been redefined several times since the instance was last accessed, UPDATE-INSTANCE-FOR-REDEFINED-CLASS is still called just once.

&KEY markers in DEFSETF lambda lists are supported, but the corresponding keywords must appear literally in the program text.

An attempt to modify read-only data SIGNALs an ERROR. Program text and quoted constants loaded from files are considered read-only data. This check is only performed for strings, not for conses, other kinds of arrays, and user-defined data types.

See also Section 31.11.2, “Macros EXT:LETF & EXT:LETF*”.

(GET-SETF-EXPANSION form &OPTIONAL environment), (EXT:GET-SETF-METHOD form &OPTIONAL environment), and (EXT:GET-SETF-METHOD-MULTIPLE-VALUE form &OPTIONAL environment) receive as optional argument environment the environment necessary for macro expansions. In DEFINE-SETF-EXPANDER and EXT:DEFINE-SETF-METHOD lambda lists, one can specify &ENVIRONMENT and a variable, which will be bound to the environment. This environment should be passed to all calls of GET-SETF-EXPANSION, EXT:GET-SETF-METHOD and EXT:GET-SETF-METHOD-MULTIPLE-VALUE. If this is done, even local macros will be interpreted as places correctly.

Additional places:

The initial value is not evaluated at compile time, just like with DEFVAR and DEFPARAMETER. Use EVAL-WHEN if you need the value at compile time.

constant variables may not be bound dynamically or lexically.

See also Section 3.3.3, “Declaration EXT:CONSTANT-NOTINLINE”.

If you need to undo the effects of a DEFCONSTANT form, PROCLAIM the symbol SPECIAL (to turn the constant variable into a dynamic variable), and then PROCLAIM it EXT:NOTSPECIAL (to turn the dynamic variable into a lexical variable).

This macro allows specifying the test for CASE, e.g.,

(fcase string= (subseq foo 0 (position #\Space foo))
  ("first" 1)
  (("second" "two") 2)
  (("true" "yes") t)
  (otherwise nil))

is the same as

(let ((var (subseq foo 0 (position #\Space foo))))
  (cond ((string= var "first") 1)
        ((or (string= var "second") (string= var "two")) 2)
        ((or (string= var "true") (string= var "yes")) t)
        (t nil)))

If you use a built-in HASH-TABLE test (see Section 18.4, “Function HASH-TABLE-TEST”) as the test (e.g., EQUAL instead of STRING= above, but not a test defined using EXT:DEFINE-HASH-TABLE-TEST), the compiler will be able to optimize the EXT:FCASE form better than the corresponding COND form.

This function checks that exactly one of its arguments is non-NIL and, if this is the case, returns its value and index in the argument list as multiple values, otherwise returns NIL.

EQ compares CHARACTERs and FIXNUMs as EQL does. No unnecessary copies are made of CHARACTERs and NUMBERs. Nevertheless, one should use EQL as it is more portable across Common Lisp implementations.

(LET ((x y)) (EQ x x)) always returns T for any Lisp object y. See also Equality of foreign values.

(FUNCTION symbol) returns the local function definition established by FLET or LABELS, if it exists, otherwise the global function definition.

(SPECIAL-OPERATOR-P symbol) returns NIL or T. If it returns T, then (SYMBOL-FUNCTION symbol) returns the (useless) special operator handler.

The macros DOLIST and DOTIMES establish a single binding for the iteration variable and assign it on each iteration.

Generic function CLOS:NO-PRIMARY-METHOD (similar to NO-APPLICABLE-METHOD) is called when there is an applicable method but no applicable primary method.

The default methods for CLOS:NO-PRIMARY-METHOD, NO-APPLICABLE-METHOD and NO-NEXT-METHOD SIGNAL an ERROR of type CLOS:METHOD-CALL-ERROR . You can find out more information about the error using functions CLOS:METHOD-CALL-ERROR-GENERIC-FUNCTION, CLOS:METHOD-CALL-ERROR-ARGUMENT-LIST, and (only for NO-NEXT-METHOD) CLOS:METHOD-CALL-ERROR-METHOD. Moreover, when the generic function has only one dispatching argument, (i.e., such an argument that not all the corresponding parameter specializers are T), an ERROR of type CLOS:METHOD-CALL-TYPE-ERROR is SIGNALed, additionally making TYPE-ERROR-DATUM and TYPE-ERROR-EXPECTED-TYPE available.

The following functions accept a structure name as the only argument. If DEFSTRUCT was given the :TYPE option (i.e., DEFSTRUCT did not define a new type), then (FIND-CLASS name) fails (and the regular CLOS Meta-Object Protocol is not applicable), but these functions still work.

The error message prefix for the first line is “*** - ”. All subsequent lines are indented by 6 characters. Long lines are broken on whitespace (see Section 30.8, “Class EXT:FILL-STREAM”).

Contrary to the recommendation of the standard, CLISP usually does print the name of the containing function to simplify debugging in batch mode, see EXT:EXIT-ON-ERROR.

Macro RESTART-CASE. In (RESTART-CASE form {restart-clause}*), the argument list can also be specified after the keyword/value pairs instead of before them, i.e., each restart-clause can be either (restart-name EXT:*ARGS* {keyword-value-pair}* {form}*) or (restart-name {keyword-value-pair}* EXT:*ARGS* {form}*).

Macro EXT:WITH-RESTARTS. The macro EXT:WITH-RESTARTS is like RESTART-CASE, except that the forms are specified after the restart clauses instead of before them, and the restarts created are not implicitly associated with any CONDITION. (EXT:WITH-RESTARTS ({restart-clause}*) {form}*) is therefore equivalent to (RESTART-CASE (PROGN {form}*) {restart-clause}*).

Function COMPUTE-RESTARTS. COMPUTE-RESTARTS and FIND-RESTART behave as specified in [ANSI CL standard]: If the optional condition argument is non-NIL, only RESTARTs associated with that CONDITION and RESTARTs associated with no CONDITION at all are considered. Therefore the effect of associating a restart to a condition is not to activate it, but to hide it from other conditions. This makes the syntax-dependent implicit association performed by RESTART-CASE nearly obsolete.

Macro EXT:MUFFLE-CERRORS. The macro (EXT:MUFFLE-CERRORS {form}*) executes the forms; when a continuable ERROR occurs whose CONTINUE RESTART can be invoked non-interactively (this includes all continuable ERRORs signaled by the function CERROR), no message is printed, instead, the CONTINUE RESTART is invoked.

Macro EXT:APPEASE-CERRORS. The macro (EXT:APPEASE-CERRORS {form}*) executes the forms; when a continuable ERROR occurs whose CONTINUE RESTART can be invoked non-interactively (this includes all continuable ERRORs SIGNALed by the function CERROR), it is reported as a WARNING, and the CONTINUE RESTART is invoked.

Macro EXT:ABORT-ON-ERROR. The macro (EXT:ABORT-ON-ERROR {form}*) executes the forms; when an ERROR occurs, or when a Control+C interrupt occurs, the error message is printed and the ABORT RESTART is invoked.