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ANSI Common Lisp  5 Data and Control Flow 5.3 Dictionary of Data and Control Flow
- Syntax:
-
eq
x y
 generalized-boolean
- Arguments and Values:
-
x - an object.
y - an object.
generalized-boolean - a generalized boolean.
- Description:
-
Returns true if its arguments are the same, identical object;
otherwise, returns false.
- Examples:
-
(eq 'a 'b) false
(eq 'a 'a) true
(eq 3 3)
true
ORfalse
(eq 3 3.0) false
(eq 3.0 3.0)
true
ORfalse
(eq #c(3 -4) #c(3 -4))
true
ORfalse
(eq #c(3 -4.0) #c(3 -4)) false
(eq (cons 'a 'b) (cons 'a 'c)) false
(eq (cons 'a 'b) (cons 'a 'b)) false
(eq '(a . b) '(a . b))
true
ORfalse
(progn (setq x (cons 'a 'b)) (eq x x)) true
(progn (setq x '(a . b)) (eq x x)) true
(eq #\A #\A)
true
ORfalse
(let ((x "Foo")) (eq x x)) true
(eq "Foo" "Foo")
true
ORfalse
(eq "Foo" (copy-seq "Foo")) false
(eq "FOO" "foo") false
(eq "string-seq" (copy-seq "string-seq")) false
(let ((x 5)) (eq x x))
true
ORfalse
- See Also:
-
eql,
equal,
equalp,
=,
Section 3.2 Compilation
- Notes:
-
Objects that appear the same when printed are not necessarily
eq to each other. Symbols that print the same
usually are eq to each other because of the use of the
intern function. However, numbers with the
same value need not be eq, and two similar
lists are usually not identical.
An implementation is permitted to make "copies" of
characters and numbers at any time.
The effect is that Common Lisp makes no guarantee that eq
is true even when both its arguments are "the same thing" if
that thing is a character or number.
Most Common Lisp operators use eql rather than
eq to compare objects, or else they default to eql
and only use eq if specifically requested to do so.
However, the following operators are defined to use eq
rather than eql in a way that cannot be overridden by the
code which employs them:
Operators that always prefer EQ over EQL
| catch |
getf |
throw |
| get |
remf |
|
| get-properties |
remprop |
- Allegro CL Implementation Details:
-
None.
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