

 
Round(3) 
User Contributed Perl Documentation 
Round(3) 
Math::Round  Perl extension for rounding numbers
use Math::Round qw(...those desired... or :all);
$rounded = round($scalar);
@rounded = round(LIST...);
$rounded = nearest($target, $scalar);
@rounded = nearest($target, LIST...);
# and other functions as described below
Math::Round supplies functions that will round numbers in different ways.
The functions round and nearest are exported by default; others
are available as described below. "use ... qw(:all)" exports all
functions.
 round LIST
 Rounds the number(s) to the nearest integer. In scalar context, returns a
single value; in list context, returns a list of values. Numbers that are
halfway between two integers are rounded "to infinity"; i.e.,
positive values are rounded up (e.g., 2.5 becomes 3) and negative values
down (e.g., 2.5 becomes 3).
Starting in Perl 5.22, the POSIX module by default exports all functions,
including one named "round". If you use both POSIX and this
module, exercise due caution.
 round_even LIST
 Rounds the number(s) to the nearest integer. In scalar context, returns a
single value; in list context, returns a list of values. Numbers that are
halfway between two integers are rounded to the nearest even number; e.g.,
2.5 becomes 2, 3.5 becomes 4, and 2.5 becomes 2.
 round_odd LIST
 Rounds the number(s) to the nearest integer. In scalar context, returns a
single value; in list context, returns a list of values. Numbers that are
halfway between two integers are rounded to the nearest odd number; e.g.,
3.5 becomes 3, 4.5 becomes 5, and 3.5 becomes 3.
 round_rand LIST
 Rounds the number(s) to the nearest integer. In scalar context, returns a
single value; in list context, returns a list of values. Numbers that are
halfway between two integers are rounded up or down in a random fashion.
For example, in a large number of trials, 2.5 will become 2 half the time
and 3 half the time.
 nearest TARGET, LIST
 Rounds the number(s) to the nearest multiple of the target value. TARGET
must be positive. In scalar context, returns a single value; in list
context, returns a list of values. Numbers that are halfway between two
multiples of the target will be rounded to infinity. For example:
nearest(10, 44) yields 40
nearest(10, 46) 50
nearest(10, 45) 50
nearest(25, 328) 325
nearest(.1, 4.567) 4.6
nearest(10, 45) 50
 nearest_ceil TARGET, LIST
 Rounds the number(s) to the nearest multiple of the target value. TARGET
must be positive. In scalar context, returns a single value; in list
context, returns a list of values. Numbers that are halfway between two
multiples of the target will be rounded to the ceiling, i.e. the next
algebraically higher multiple. For example:
nearest_ceil(10, 44) yields 40
nearest_ceil(10, 45) 50
nearest_ceil(10, 45) 40
 nearest_floor TARGET, LIST
 Rounds the number(s) to the nearest multiple of the target value. TARGET
must be positive. In scalar context, returns a single value; in list
context, returns a list of values. Numbers that are halfway between two
multiples of the target will be rounded to the floor, i.e. the next
algebraically lower multiple. For example:
nearest_floor(10, 44) yields 40
nearest_floor(10, 45) 40
nearest_floor(10, 45) 50
 nearest_rand TARGET, LIST
 Rounds the number(s) to the nearest multiple of the target value. TARGET
must be positive. In scalar context, returns a single value; in list
context, returns a list of values. Numbers that are halfway between two
multiples of the target will be rounded up or down in a random fashion.
For example, in a large number of trials, "nearest(10, 45)" will
yield 40 half the time and 50 half the time.
 nlowmult TARGET, LIST
 Returns the next lower multiple of the number(s) in LIST. TARGET must be
positive. In scalar context, returns a single value; in list context,
returns a list of values. Numbers that are between two multiples of the
target will be adjusted to the nearest multiples of LIST that are
algebraically lower. For example:
nlowmult(10, 44) yields 40
nlowmult(10, 46) 40
nlowmult(25, 328) 325
nlowmult(.1, 4.567) 4.5
nlowmult(10, 41) 50
 nhimult TARGET, LIST
 Returns the next higher multiple of the number(s) in LIST. TARGET must be
positive. In scalar context, returns a single value; in list context,
returns a list of values. Numbers that are between two multiples of the
target will be adjusted to the nearest multiples of LIST that are
algebraically higher. For example:
nhimult(10, 44) yields 50
nhimult(10, 46) 50
nhimult(25, 328) 350
nhimult(.1, 4.512) 4.6
nhimult(10, 49) 40
The variable $Math::Round::half is used by most routines in
this module. Its value is very slightly larger than 0.5, for reasons explained
below. If you find that your application does not deliver the expected
results, you may reset this variable at will.
Floatingpoint numbers are, of course, a rational subset of the real numbers, so
calculations with them are not always exact. Numbers that are supposed to be
halfway between two others may surprise you; for instance, 0.85 may not be
exactly halfway between 0.8 and 0.9, and (0.75  0.7) may not be the same as
(0.85  0.8).
In order to give more predictable results, these routines use a value for
onehalf that is slightly larger than 0.5. Nevertheless, if the numbers to be
rounded are stored as floatingpoint, they will be subject as usual to the
mercies of your hardware, your C compiler, etc.
Math::Round was written by Geoffrey Rommel <GROMMEL@cpan.org> in October
2000.
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