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

Returns the float truncated to an Integer.

Synonyms are to_i, to_int, and truncate.

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

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.

Copyright

Author: Keiju ISHITSUKA (SHL Japan Inc.)

Only the object nil responds true to nil?.

Object.new.nil?   #=> false
nil.nil?          #=> true

Removes the tainted mark from the object.

See taint for more information.

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.

Synonyms are to_int, floor, ceil, truncate.

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