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ANSI Common Lisp  5 Data and Control Flow 5.3 Dictionary of Data and Control Flow
- Syntax:
-
eql
x y
 generalized-boolean
- Arguments and Values:
-
x - an object.
y - an object.
generalized-boolean - a generalized boolean.
- Description:
-
The value of eql is true of two objects, x and
y, in the following cases:
- 1. If x and y are eq.
- 2. If x and y are both numbers
of the same type and the same value.
- 3. If they are both characters that represent the
same character.
Otherwise the value of eql is false.
If an implementation supports positive and negative zeros as distinct values,
then (eql 0.0 -0.0) returns false.
Otherwise, when the syntax -0.0 is read it is interpreted as the value 0.0,
and so (eql 0.0 -0.0) returns true.
- Examples:
-
(eql 'a 'b) false
(eql 'a 'a) true
(eql 3 3) true
(eql 3 3.0) false
(eql 3.0 3.0) true
(eql #c(3 -4) #c(3 -4)) true
(eql #c(3 -4.0) #c(3 -4)) false
(eql (cons 'a 'b) (cons 'a 'c)) false
(eql (cons 'a 'b) (cons 'a 'b)) false
(eql '(a . b) '(a . b))
true
ORfalse
(progn (setq x (cons 'a 'b)) (eql x x)) true
(progn (setq x '(a . b)) (eql x x)) true
(eql #\A #\A) true
(eql "Foo" "Foo")
true
ORfalse
(eql "Foo" (copy-seq "Foo")) false
(eql "FOO" "foo") false
Normally (eql 1.0s0 1.0d0) is false, under the assumption
that 1.0s0 and 1.0d0 are of distinct data types.
However, implementations that do not provide four distinct floating-point
formats are permitted to "collapse" the four formats into some
smaller number of them; in such an implementation (eql 1.0s0 1.0d0)
might be true.
- See Also:
-
eq,
equal,
equalp,
=,
char=
- Notes:
-
eql is the same as eq, except that if the
arguments are characters or numbers
of the same type then their
values are compared. Thus eql tells whether two objects
are conceptually the same, whereas eq tells whether two
objects are implementationally identical. It is for this reason
that eql, not eq, is the default comparison predicate
for operators that take sequences
as arguments.
eql may not be true of two floats
even when they represent the same
value. = is used to compare
mathematical values.
Two complex numbers are considered to be eql
if their real parts are eql
and their imaginary parts are eql.
For example, (eql #C(4 5) #C(4 5)) is true and
(eql #C(4 5) #C(4.0 5.0)) is false.
Note that while (eql #C(5.0 0.0) 5.0) is false,
(eql #C(5 0) 5) is true.
In the case of (eql #C(5.0 0.0) 5.0) the
two arguments are of different types,
and so cannot satisfy eql.
In the case of (eql #C(5 0) 5),
#C(5 0) is not a complex number, but
is automatically reduced
to the integer 5.
- Allegro CL Implementation Details:
-
None.
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