mirror/emacs
1
0
Fork 0
mirror of https://git.savannah.gnu.org/git/emacs.git synced 2025-01-03 11:33:37 +00:00
Code Issues Releases Activity

(Numeric Conversions): Not just floor', but also truncate',

Browse Source 
`ceiling' and `round' accept optional argument DIVISOR.
This commit is contained in:
Luc Teirlinck 2003-11-12 21:30:14 +00:00
parent c5e2fb05c1
commit fa091c040c
1 changed files with 17 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
lispref/numbers.texi
View File

@ -168,8 +168,8 @@ to write negative floating point numbers, as in @samp{-1.0}.
@cindex negative infinity
@cindex infinity
@cindex NaN
Most modern computers support the @acronym{IEEE} floating point standard, which
provides for positive infinity and negative infinity as floating point
Most modern computers support the @acronym{IEEE} floating point standard,
which provides for positive infinity and negative infinity as floating point
values. It also provides for a class of values called NaN or
``not-a-number''; numerical functions return such values in cases where
there is no correct answer. For example, @code{(sqrt -1.0)} returns a
@ -189,8 +189,8 @@ these special floating point values:
@end table
In addition, the value @code{-0.0} is distinguishable from ordinary
zero in @acronym{IEEE} floating point (although @code{equal} and @code{=} consider
them equal values).
zero in @acronym{IEEE} floating point (although @code{equal} and
@code{=} consider them equal values).
You can use @code{logb} to extract the binary exponent of a floating
point number (or estimate the logarithm of an integer):
@ -379,10 +379,16 @@ it unchanged.
@end defun
There are four functions to convert floating point numbers to integers;
they differ in how they round. These functions accept integer arguments
also, and return such arguments unchanged.
they differ in how they round. All accept an argument @var{number}
and an optional argument @var{divisor}. Both arguments may be
integers or floating point numbers. @var{divisor} may also be
@code{nil}. If @var{divisor} is @code{nil} or omitted, these
functions convert @var{number} to an integer, or return it unchanged
if it already is an integer. If @var{divisor} is non-@code{nil}, they
divide @var{number} by @var{divisor} and convert the result to an
integer. An @code{arith-error} results if @var{divisor} is 0.
@defun truncate number
@defun truncate number &optional divisor
This returns @var{number}, converted to an integer by rounding towards
zero.
@ -402,10 +408,8 @@ zero.
This returns @var{number}, converted to an integer by rounding downward
(towards negative infinity).
If @var{divisor} is specified, @code{floor} divides @var{number} by
@var{divisor} and then converts to an integer; this uses the kind of
division operation that corresponds to @code{mod}, rounding downward.
An @code{arith-error} results if @var{divisor} is 0.
If @var{divisor} is specified, this uses the kind of division
operation that corresponds to @code{mod}, rounding downward.
@example
(floor 1.2)
@ -421,7 +425,7 @@ An @code{arith-error} results if @var{divisor} is 0.
@end example
@end defun
@defun ceiling number
@defun ceiling number &optional divisor
This returns @var{number}, converted to an integer by rounding upward
(towards positive infinity).
@ -437,7 +441,7 @@ This returns @var{number}, converted to an integer by rounding upward
@end example
@end defun
@defun round number
@defun round number &optional divisor
This returns @var{number}, converted to an integer by rounding towards the
nearest integer. Rounding a value equidistant between two integers
may choose the integer closer to zero, or it may prefer an even integer,