@cindex hex numbers
@cindex octal numbers
@cindex reading numbers in hex, octal, and binary
- In addition, the Lisp reader recognizes a syntax for integers in
-bases other than 10: @samp{#B@var{integer}} reads @var{integer} in
-binary (radix 2), @samp{#O@var{integer}} reads @var{integer} in octal
-(radix 8), @samp{#X@var{integer}} reads @var{integer} in hexadecimal
-(radix 16), and @samp{#@var{radix}r@var{integer}} reads @var{integer}
-in radix @var{radix} (where @var{radix} is between 2 and 36,
-inclusively). Case is not significant for the letter after @samp{#}
-(@samp{B}, @samp{O}, etc.) that denotes the radix.
+ The syntax for integers in bases other than 10 uses @samp{#}
+followed by a letter that specifies the radix: @samp{b} for binary,
+@samp{o} for octal, @samp{x} for hex, or @samp{@var{radix}r} to
+specify radix @var{radix}. Case is not significant for the letter
+that specifies the radix. Thus, @samp{#b@var{integer}} reads
+@var{integer} in binary, and @samp{#@var{radix}r@var{integer}} reads
+@var{integer} in radix @var{radix}. Allowed values of @var{radix} run
+from 2 to 36. For example:
+
+@example
+#b101100 @result{} 44
+#o54 @result{} 44
+#x2c @result{} 44
+#24r1k @result{} 44
+@end example
To understand how various functions work on integers, especially the
bitwise operators (@pxref{Bitwise Operations}), it is often helpful to
@node Predicates on Numbers
@section Type Predicates for Numbers
- The functions in this section test whether the argument is a number or
-whether it is a certain sort of number. The functions @code{integerp}
-and @code{floatp} can take any type of Lisp object as argument (the
-predicates would not be of much use otherwise); but the @code{zerop}
-predicate requires a number as its argument. See also
-@code{integer-or-marker-p} and @code{number-or-marker-p}, in
-@ref{Predicates on Markers}.
+ The functions in this section test for numbers, or for a specific
+type of number. The functions @code{integerp} and @code{floatp} can
+take any type of Lisp object as argument (they would not be of much
+use otherwise), but the @code{zerop} predicate requires a number as
+its argument. See also @code{integer-or-marker-p} and
+@code{number-or-marker-p}, in @ref{Predicates on Markers}.
@defun floatp object
This predicate tests whether its argument is a floating point
This predicate tests whether its argument is zero, and returns @code{t}
if so, @code{nil} otherwise. The argument must be a number.
-These two forms are equivalent: @code{(zerop x)} @equiv{} @code{(= x 0)}.
+@code{(zerop x)} is equivalent to @code{(= x 0)}.
@end defun
@node Comparison of Numbers
can, even for comparing integers, just in case we change the
representation of integers in a future Emacs version.
- Sometimes it is useful to compare numbers with @code{equal}; it treats
-two numbers as equal if they have the same data type (both integers, or
-both floating point) and the same value. By contrast, @code{=} can
-treat an integer and a floating point number as equal.
+ Sometimes it is useful to compare numbers with @code{equal}; it
+treats two numbers as equal if they have the same data type (both
+integers, or both floating point) and the same value. By contrast,
+@code{=} can treat an integer and a floating point number as equal.
+@xref{Equality Predicates}.
There is another wrinkle: because floating point arithmetic is not
exact, it is often a bad idea to check for equality of two floating
returns @code{t} if so, @code{nil} otherwise.
@end defun
+@defun eql value1 value2
+This function acts like @code{eq} except when both arguments are
+numbers. It compares numbers by type and numberic value, so that
+@code{(eql 1.0 1)} returns @code{nil}, but @code{(eql 1.0 1.0)} and
+@code{(eql 1 1)} both return @code{t}.
+@end defun
+
@defun /= number-or-marker1 number-or-marker2
This function tests whether its arguments are numerically equal, and
returns @code{t} if they are not, and @code{nil} if they are.
@defun max number-or-marker &rest numbers-or-markers
This function returns the largest of its arguments.
-If any of the argument is floating-point, the value is returned
+If any of the arguments is floating-point, the value is returned
as floating point, even if it was given as an integer.
@example
@defun min number-or-marker &rest numbers-or-markers
This function returns the smallest of its arguments.
-If any of the argument is floating-point, the value is returned
+If any of the arguments is floating-point, the value is returned
as floating point, even if it was given as an integer.
@example
@defun expt x y
This function returns @var{x} raised to power @var{y}. If both
arguments are integers and @var{y} is positive, the result is an
-integer; in this case, it is truncated to fit the range of possible
-integer values.
+integer; in this case, overflow causes truncation, so watch out.
@end defun
@defun sqrt arg