Returns the index of the last element for which object == element.
With argument object given, returns the index of the last such element found:
a = [:foo, 'bar', 2, 'bar'] a.rindex('bar') # => 3
Returns nil if no such object found.
With a block given, calls the block with each successive element; returns the index of the last element for which the block returns a truthy value:
a = [:foo, 'bar', 2, 'bar'] a.rindex {|element| element == 'bar' } # => 3
Returns nil if the block never returns a truthy value.
When neither an argument nor a block is given, returns a new Enumerator.
Related: see Methods for Querying.
Returns the new string formed by joining the converted elements of self; for each element element:
Converts recursively using element.join(separator) if element is a kind_of?(Array).
Otherwise, converts using element.to_s.
With no argument given, joins using the output field separator, $,:
a = [:foo, 'bar', 2] $, # => nil a.join # => "foobar2"
With string argument separator given, joins using that separator:
a = [:foo, 'bar', 2] a.join("\n") # => "foo\nbar\n2"
Joins recursively for nested arrays:
a = [:foo, [:bar, [:baz, :bat]]] a.join # => "foobarbazbat"
Related: see Methods for Converting.
With a block given, calls the block with each element of self; returns a new array whose elements are the return values from the block:
a = [:foo, 'bar', 2] a1 = a.map {|element| element.class } a1 # => [Symbol, String, Integer]
With no block given, returns a new Enumerator.
Related: collect!; see also Methods for Converting.
With a block given, calls the block with each element of self and replaces the element with the block’s return value; returns self:
a = [:foo, 'bar', 2] a.map! { |element| element.class } # => [Symbol, String, Integer]
With no block given, returns a new Enumerator.
Related: collect; see also Methods for Converting.
Returns whether for some element element in self, object == element:
[0, 1, 2].include?(2) # => true [0, 1, 2].include?(2.0) # => true [0, 1, 2].include?(2.1) # => false
Related: see Methods for Querying.
When a block and a positive integer-convertible object argument count (0 < count <= self.size) are given, calls the block with each combination of self of size count; returns self:
a = %w[a b c] # => ["a", "b", "c"] a.combination(2) {|combination| p combination } # => ["a", "b", "c"]
Output:
["a", "b"] ["a", "c"] ["b", "c"]
The order of the yielded combinations is not guaranteed.
When count is zero, calls the block once with a new empty array:
a.combination(0) {|combination| p combination } [].combination(0) {|combination| p combination }
Output:
[] []
When count is negative or larger than self.size and self is non-empty, does not call the block:
a.combination(-1) {|combination| fail 'Cannot happen' } # => ["a", "b", "c"] a.combination(4) {|combination| fail 'Cannot happen' } # => ["a", "b", "c"]
With no block given, returns a new Enumerator.
Related: Array#permutation; see also Methods for Iterating.
Builds a command line string from an argument list array joining all elements escaped for the Bourne shell and separated by a space.
See Shellwords.shelljoin for details.
Returns a string containing the place-value representation of self in radix base (in 2..36).
12345.to_s # => "12345" 12345.to_s(2) # => "11000000111001" 12345.to_s(8) # => "30071" 12345.to_s(10) # => "12345" 12345.to_s(16) # => "3039" 12345.to_s(36) # => "9ix" 78546939656932.to_s(36) # => "rubyrules"
Raises an exception if base is out of range.
Since self is already an Integer, always returns true.
Returns the imaginary value for self:
Complex.rect(7).imag # => 0 Complex.rect(9, -4).imag # => -4
If self was created with polar coordinates, the returned value is computed, and may be inexact:
Complex.polar(1, Math::PI/4).imag # => 0.7071067811865476 # Square root of 2.
Returns the absolute value (magnitude) for self; see polar coordinates:
Complex.polar(-1, 0).abs # => 1.0
If self was created with rectangular coordinates, the returned value is computed, and may be inexact:
Complex.rectangular(1, 1).abs # => 1.4142135623730951 # The square root of 2.
Returns a string representation of self:
Complex.rect(2).inspect # => "(2+0i)" Complex.rect(-8, 6).inspect # => "(-8+6i)" Complex.rect(0, Rational(1, 2)).inspect # => "(0+(1/2)*i)" Complex.rect(0, Float::INFINITY).inspect # => "(0+Infinity*i)" Complex.rect(Float::NAN, Float::NAN).inspect # => "(NaN+NaN*i)"
Returns true if both self.real.finite? and self.imag.finite? are true, false otherwise:
Complex.rect(1, 1).finite? # => true Complex.rect(Float::INFINITY, 0).finite? # => false
Related: Numeric#finite?, Float#finite?.
Returns the absolute value of self.
12.abs #=> 12 (-34.56).abs #=> 34.56 -34.56.abs #=> 34.56
Returns true if self is a finite number, false otherwise.
Inserts the given other_string into self; returns self.
If the Integer index is positive, inserts other_string at offset index:
'foo'.insert(1, 'bar') # => "fbaroo"
If the Integer index is negative, counts backward from the end of self and inserts other_string at offset index+1 (that is, after self[index]):
'foo'.insert(-2, 'bar') # => "fobaro"
Returns a MatchData object (or nil) based on self and the given pattern.
Note: also updates Global Variables at Regexp.
Computes regexp by converting pattern (if not already a Regexp).
regexp = Regexp.new(pattern)
Computes matchdata, which will be either a MatchData object or nil (see Regexp#match):
matchdata = regexp.match(self)
With no block given, returns the computed matchdata:
'foo'.match('f') # => #<MatchData "f"> 'foo'.match('o') # => #<MatchData "o"> 'foo'.match('x') # => nil
If Integer argument offset is given, the search begins at index offset:
'foo'.match('f', 1) # => nil 'foo'.match('o', 1) # => #<MatchData "o">
With a block given, calls the block with the computed matchdata and returns the block’s return value:
'foo'.match(/o/) {|matchdata| matchdata } # => #<MatchData "o"> 'foo'.match(/x/) {|matchdata| matchdata } # => nil 'foo'.match(/f/, 1) {|matchdata| matchdata } # => nil
Returns true or false based on whether a match is found for self and pattern.
Note: does not update Global Variables at Regexp.
Computes regexp by converting pattern (if not already a Regexp).
regexp = Regexp.new(pattern)
Returns true if self+.match(regexp) returns a MatchData object, false otherwise:
'foo'.match?(/o/) # => true 'foo'.match?('o') # => true 'foo'.match?(/x/) # => false
If Integer argument offset is given, the search begins at index offset:
'foo'.match?('f', 1) # => false 'foo'.match?('o', 1) # => true
Returns the integer index of the first match for the given argument, or nil if none found; the search of self is forward, and begins at position offset (in characters).
With string argument substring, returns the index of the first matching substring in self:
'foo'.index('f') # => 0 'foo'.index('o') # => 1 'foo'.index('oo') # => 1 'foo'.index('ooo') # => nil 'тест'.index('с') # => 2 'こんにちは'.index('ち') # => 3
With Regexp argument regexp, returns the index of the first match in self:
'foo'.index(/o./) # => 1 'foo'.index(/.o/) # => 0
With positive integer offset, begins the search at position offset:
'foo'.index('o', 1) # => 1 'foo'.index('o', 2) # => 2 'foo'.index('o', 3) # => nil 'тест'.index('с', 1) # => 2 'こんにちは'.index('ち', 2) # => 3
With negative integer offset, selects the search position by counting backward from the end of self:
'foo'.index('o', -1) # => 2 'foo'.index('o', -2) # => 1 'foo'.index('o', -3) # => 1 'foo'.index('o', -4) # => nil 'foo'.index(/o./, -2) # => 1 'foo'.index(/.o/, -2) # => 1
Related: String#rindex.
Returns the 0-based integer index of a substring of self specified by object (a string or Regexp) and offset, or nil if there is no such substring; the returned index is the count of bytes (not characters).
When object is a string, returns the index of the first found substring equal to object:
s = 'foo' # => "foo" s.size # => 3 # Three 1-byte characters. s.bytesize # => 3 # Three bytes. s.byteindex('f') # => 0 s.byteindex('o') # => 1 s.byteindex('oo') # => 1 s.byteindex('ooo') # => nil
When object is a Regexp, returns the index of the first found substring matching object; updates Regexp-related global variables:
s = 'foo' s.byteindex(/f/) # => 0 $~ # => #<MatchData "f"> s.byteindex(/o/) # => 1 s.byteindex(/oo/) # => 1 s.byteindex(/ooo/) # => nil $~ # => nil
Integer argument offset, if given, specifies the 0-based index of the byte where searching is to begin.
When offset is non-negative, searching begins at byte position offset:
s = 'foo' s.byteindex('o', 1) # => 1 s.byteindex('o', 2) # => 2 s.byteindex('o', 3) # => nil
When offset is negative, counts backward from the end of self:
s = 'foo' s.byteindex('o', -1) # => 2 s.byteindex('o', -2) # => 1 s.byteindex('o', -3) # => 1 s.byteindex('o', -4) # => nil
Raises IndexError if the byte at offset is not the first byte of a character:
s = "\uFFFF\uFFFF" # => "\uFFFF\uFFFF" s.size # => 2 # Two 3-byte characters. s.bytesize # => 6 # Six bytes. s.byteindex("\uFFFF") # => 0 s.byteindex("\uFFFF", 1) # Raises IndexError s.byteindex("\uFFFF", 2) # Raises IndexError s.byteindex("\uFFFF", 3) # => 3 s.byteindex("\uFFFF", 4) # Raises IndexError s.byteindex("\uFFFF", 5) # Raises IndexError s.byteindex("\uFFFF", 6) # => nil
Related: see Querying.
Returns the Integer index of the last occurrence of the given substring, or nil if none found:
'foo'.rindex('f') # => 0 'foo'.rindex('o') # => 2 'foo'.rindex('oo') # => 1 'foo'.rindex('ooo') # => nil
Returns the Integer index of the last match for the given Regexp regexp, or nil if none found:
'foo'.rindex(/f/) # => 0 'foo'.rindex(/o/) # => 2 'foo'.rindex(/oo/) # => 1 'foo'.rindex(/ooo/) # => nil
The last match means starting at the possible last position, not the last of longest matches.
'foo'.rindex(/o+/) # => 2 $~ #=> #<MatchData "o">
To get the last longest match, needs to combine with negative lookbehind.
'foo'.rindex(/(?<!o)o+/) # => 1 $~ #=> #<MatchData "oo">
Or String#index with negative lookforward.
'foo'.index(/o+(?!.*o)/) # => 1 $~ #=> #<MatchData "oo">
Integer argument offset, if given and non-negative, specifies the maximum starting position in the string to end the search:
'foo'.rindex('o', 0) # => nil 'foo'.rindex('o', 1) # => 1 'foo'.rindex('o', 2) # => 2 'foo'.rindex('o', 3) # => 2
If offset is a negative Integer, the maximum starting position in the string to end the search is the sum of the string’s length and offset:
'foo'.rindex('o', -1) # => 2 'foo'.rindex('o', -2) # => 1 'foo'.rindex('o', -3) # => nil 'foo'.rindex('o', -4) # => nil
Related: String#index.