Rounds float
to a given precision in decimal digits (default 0 digits).
Precision may be negative. Returns a floating point number when ndigits
is more than zero.
1.4.round #=> 1 1.5.round #=> 2 1.6.round #=> 2 (-1.5).round #=> -2 1.234567.round(2) #=> 1.23 1.234567.round(3) #=> 1.235 1.234567.round(4) #=> 1.2346 1.234567.round(5) #=> 1.23457 34567.89.round(-5) #=> 0 34567.89.round(-4) #=> 30000 34567.89.round(-3) #=> 35000 34567.89.round(-2) #=> 34600 34567.89.round(-1) #=> 34570 34567.89.round(0) #=> 34568 34567.89.round(1) #=> 34567.9 34567.89.round(2) #=> 34567.89 34567.89.round(3) #=> 34567.89
Return values corresponding to the value of float
:
finite
nil
-Infinity
-1
+Infinity
1
For example:
(0.0).infinite? #=> nil (-1.0/0.0).infinite? #=> -1 (+1.0/0.0).infinite? #=> 1
Returns true
if float
is a valid IEEE floating point number (it is not infinite, and Float#nan?
is false
).
Deletes the named directory. Raises a subclass of SystemCallError
if the directory isn’t empty.
Deletes the named files, returning the number of names passed as arguments. Raises an exception on any error. See also Dir::rmdir
.
Truncates the file file_name to be at most integer bytes long. Not available on all platforms.
f = File.new("out", "w") f.write("1234567890") #=> 10 f.close #=> nil File.truncate("out", 5) #=> 0 File.size("out") #=> 5
Truncates file to at most integer bytes. The file must be opened for writing. Not available on all platforms.
f = File.new("out", "w") f.syswrite("1234567890") #=> 10 f.truncate(5) #=> 0 f.close() #=> nil File.size("out") #=> 5
mathn serves to make mathematical operations more precise in Ruby and to integrate other mathematical standard libraries.
Without mathn:
3 / 2 => 1 # Integer
With mathn:
3 / 2 => 3/2 # Rational
mathn keeps value in exact terms.
Without mathn:
20 / 9 * 3 * 14 / 7 * 3 / 2 # => 18
With mathn:
20 / 9 * 3 * 14 / 7 * 3 / 2 # => 20
When you require ‘mathn’, the libraries for Prime
, CMath
, Matrix
and Vector
are also loaded.
Author: Keiju ISHITSUKA (SHL Japan Inc.)
Deprecated method that is equivalent to taint
.
Deprecated method that is equivalent to tainted?
.
Round to the nearest integer (by default), returning the result as a BigDecimal
.
BigDecimal('3.14159').round #=> 3 BigDecimal('8.7').round #=> 9 BigDecimal('-9.9').round #=> -10
If n is specified and positive, the fractional part of the result has no more than that many digits.
If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.
BigDecimal('3.14159').round(3) #=> 3.142 BigDecimal('13345.234').round(-2) #=> 13300.0
The value of the optional mode argument can be used to determine how rounding is performed; see BigDecimal.mode
.
Returns nil, -1, or +1 depending on whether the value is finite, -Infinity, or +Infinity.
Returns True if the value is finite (not NaN or infinite).
Truncate to the nearest integer (by default), returning the result as a BigDecimal
.
BigDecimal('3.14159').truncate #=> 3 BigDecimal('8.7').truncate #=> 8 BigDecimal('-9.9').truncate #=> -9
If n is specified and positive, the fractional part of the result has no more than that many digits.
If n is specified and negative, at least that many digits to the left of the decimal point will be 0 in the result.
BigDecimal('3.14159').truncate(3) #=> 3.141 BigDecimal('13345.234').truncate(-2) #=> 13300.0
As int
is already an Integer
, all these methods simply return the receiver.
Rounds int
to a given precision in decimal digits (default 0 digits).
Precision may be negative. Returns a floating point number when ndigits
is positive, self
for zero, and round down for negative.
1.round #=> 1 1.round(2) #=> 1.0 15.round(-1) #=> 20
Returns the truncated value (toward zero).
Rational(3).truncate #=> 3 Rational(2, 3).truncate #=> 0 Rational(-3, 2).truncate #=> -1 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 '%f' % Rational('-123.456').truncate(+1) #=> "-123.400000" '%f' % Rational('-123.456').truncate(-1) #=> "-120.000000"
Returns the truncated value (toward the nearest integer; 0.5 => 1; -0.5 => -1).
Rational(3).round #=> 3 Rational(2, 3).round #=> 1 Rational(-3, 2).round #=> -2 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 '%f' % Rational('-123.456').round(+1) #=> "-123.500000" '%f' % Rational('-123.456').round(-1) #=> "-120.000000"
Returns true if the date is Sunday.
Rounds sub seconds to a given precision in decimal digits (0 digits by default). It returns a new Time
object. ndigits
should be zero or positive integer.
require 'time' t = Time.utc(2010,3,30, 5,43,"25.123456789".to_r) p t.iso8601(10) #=> "2010-03-30T05:43:25.1234567890Z" p t.round.iso8601(10) #=> "2010-03-30T05:43:25.0000000000Z" p t.round(0).iso8601(10) #=> "2010-03-30T05:43:25.0000000000Z" p t.round(1).iso8601(10) #=> "2010-03-30T05:43:25.1000000000Z" p t.round(2).iso8601(10) #=> "2010-03-30T05:43:25.1200000000Z" p t.round(3).iso8601(10) #=> "2010-03-30T05:43:25.1230000000Z" p t.round(4).iso8601(10) #=> "2010-03-30T05:43:25.1235000000Z" p t.round(5).iso8601(10) #=> "2010-03-30T05:43:25.1234600000Z" p t.round(6).iso8601(10) #=> "2010-03-30T05:43:25.1234570000Z" p t.round(7).iso8601(10) #=> "2010-03-30T05:43:25.1234568000Z" p t.round(8).iso8601(10) #=> "2010-03-30T05:43:25.1234567900Z" p t.round(9).iso8601(10) #=> "2010-03-30T05:43:25.1234567890Z" p t.round(10).iso8601(10) #=> "2010-03-30T05:43:25.1234567890Z" t = Time.utc(1999,12,31, 23,59,59) p((t + 0.4).round.iso8601(3)) #=> "1999-12-31T23:59:59.000Z" p((t + 0.49).round.iso8601(3)) #=> "1999-12-31T23:59:59.000Z" p((t + 0.5).round.iso8601(3)) #=> "2000-01-01T00:00:00.000Z" p((t + 1.4).round.iso8601(3)) #=> "2000-01-01T00:00:00.000Z" p((t + 1.49).round.iso8601(3)) #=> "2000-01-01T00:00:00.000Z" p((t + 1.5).round.iso8601(3)) #=> "2000-01-01T00:00:01.000Z" t = Time.utc(1999,12,31, 23,59,59) p (t + 0.123456789).round(4).iso8601(6) #=> "1999-12-31T23:59:59.123500Z"
Returns true
if time represents Sunday.
t = Time.local(1990, 4, 1) #=> 1990-04-01 00:00:00 -0600 t.sunday? #=> true
Pushes back bytes (passed as a parameter) onto ios, such that a subsequent buffered read will return it. Only one byte may be pushed back before a subsequent read operation (that is, you will be able to read only the last of several bytes that have been pushed back). Has no effect with unbuffered reads (such as IO#sysread
).
f = File.new("testfile") #=> #<File:testfile> b = f.getbyte #=> 0x38 f.ungetbyte(b) #=> nil f.getbyte #=> 0x38