When invoked with a block, yield all repeated permutations of length n of the elements of the array, then return the array itself.
The implementation makes no guarantees about the order in which the repeated permutations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2] a.repeated_permutation(1).to_a #=> [[1], [2]] a.repeated_permutation(2).to_a #=> [[1,1],[1,2],[2,1],[2,2]] a.repeated_permutation(3).to_a #=> [[1,1,1],[1,1,2],[1,2,1],[1,2,2], # [2,1,1],[2,1,2],[2,2,1],[2,2,2]] a.repeated_permutation(0).to_a #=> [[]] # one permutation of length 0
When invoked with a block, yields all repeated combinations of length n of elements from the array and then returns the array itself.
The implementation makes no guarantees about the order in which the repeated combinations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2, 3] a.repeated_combination(1).to_a #=> [[1], [2], [3]] a.repeated_combination(2).to_a #=> [[1,1],[1,2],[1,3],[2,2],[2,3],[3,3]] a.repeated_combination(3).to_a #=> [[1,1,1],[1,1,2],[1,1,3],[1,2,2],[1,2,3], # [1,3,3],[2,2,2],[2,2,3],[2,3,3],[3,3,3]] a.repeated_combination(4).to_a #=> [[1,1,1,1],[1,1,1,2],[1,1,1,3],[1,1,2,2],[1,1,2,3], # [1,1,3,3],[1,2,2,2],[1,2,2,3],[1,2,3,3],[1,3,3,3], # [2,2,2,2],[2,2,2,3],[2,2,3,3],[2,3,3,3],[3,3,3,3]] a.repeated_combination(0).to_a #=> [[]] # one combination of length 0
Creates a new Enumerator which will enumerate by calling method on obj, passing args if any. What was yielded by method becomes values of enumerator.
If a block is given, it will be used to calculate the size of the enumerator without the need to iterate it (see Enumerator#size).
str = "xyz" enum = str.enum_for(:each_byte) enum.each { |b| puts b } # => 120 # => 121 # => 122 # protect an array from being modified by some_method a = [1, 2, 3] some_method(a.to_enum) # String#split in block form is more memory-effective: very_large_string.split("|") { |chunk| return chunk if chunk.include?('DATE') } # This could be rewritten more idiomatically with to_enum: very_large_string.to_enum(:split, "|").lazy.grep(/DATE/).first
It is typical to call to_enum when defining methods for a generic Enumerable, in case no block is passed.
Here is such an example, with parameter passing and a sizing block:
module Enumerable # a generic method to repeat the values of any enumerable def repeat(n) raise ArgumentError, "#{n} is negative!" if n < 0 unless block_given? return to_enum(__method__, n) do # __method__ is :repeat here sz = size # Call size and multiply by n... sz * n if sz # but return nil if size itself is nil end end each do |*val| n.times { yield *val } end end end %i[hello world].repeat(2) { |w| puts w } # => Prints 'hello', 'hello', 'world', 'world' enum = (1..14).repeat(3) # => returns an Enumerator when called without a block enum.first(4) # => [1, 1, 1, 2] enum.size # => 42
Creates a new Enumerator which will enumerate by calling method on obj, passing args if any. What was yielded by method becomes values of enumerator.
If a block is given, it will be used to calculate the size of the enumerator without the need to iterate it (see Enumerator#size).
str = "xyz" enum = str.enum_for(:each_byte) enum.each { |b| puts b } # => 120 # => 121 # => 122 # protect an array from being modified by some_method a = [1, 2, 3] some_method(a.to_enum) # String#split in block form is more memory-effective: very_large_string.split("|") { |chunk| return chunk if chunk.include?('DATE') } # This could be rewritten more idiomatically with to_enum: very_large_string.to_enum(:split, "|").lazy.grep(/DATE/).first
It is typical to call to_enum when defining methods for a generic Enumerable, in case no block is passed.
Here is such an example, with parameter passing and a sizing block:
module Enumerable # a generic method to repeat the values of any enumerable def repeat(n) raise ArgumentError, "#{n} is negative!" if n < 0 unless block_given? return to_enum(__method__, n) do # __method__ is :repeat here sz = size # Call size and multiply by n... sz * n if sz # but return nil if size itself is nil end end each do |*val| n.times { yield *val } end end end %i[hello world].repeat(2) { |w| puts w } # => Prints 'hello', 'hello', 'world', 'world' enum = (1..14).repeat(3) # => returns an Enumerator when called without a block enum.first(4) # => [1, 1, 1, 2] enum.size # => 42
Convert an object to YAML. See Psych.dump for more information on the available options.
Returns the singleton class of obj. This method creates a new singleton class if obj does not have one.
If obj is nil, true, or false, it returns NilClass, TrueClass, or FalseClass, respectively. If obj is an Integer, a Float or a Symbol, it raises a TypeError.
Object.new.singleton_class #=> #<Class:#<Object:0xb7ce1e24>> String.singleton_class #=> #<Class:String> nil.singleton_class #=> NilClass
Returns an array of the names of singleton methods for obj. If the optional all parameter is true, the list will include methods in modules included in obj. Only public and protected singleton methods are returned.
module Other def three() end end class Single def Single.four() end end a = Single.new def a.one() end class << a include Other def two() end end Single.singleton_methods #=> [:four] a.singleton_methods(false) #=> [:two, :one] a.singleton_methods #=> [:two, :one, :three]
Returns an array of instance variable names for the receiver. Note that simply defining an accessor does not create the corresponding instance variable.
class Fred attr_accessor :a1 def initialize @iv = 3 end end Fred.new.instance_variables #=> [:@iv]
Returns true if obj is an instance of the given class. See also Object#kind_of?.
class A; end class B < A; end class C < B; end b = B.new b.instance_of? A #=> false b.instance_of? B #=> true b.instance_of? C #=> false
Similar to method, searches singleton method only.
class Demo def initialize(n) @iv = n end def hello() "Hello, @iv = #{@iv}" end end k = Demo.new(99) def k.hi "Hi, @iv = #{@iv}" end m = k.singleton_method(:hi) m.call #=> "Hi, @iv = 99" m = k.singleton_method(:hello) #=> NameError
Invokes the child class’s to_i method to convert num to an integer.
1.0.class #=> Float 1.0.to_int.class #=> Integer 1.0.to_i.class #=> Integer
Returns an array of grapheme clusters in str. This is a shorthand for str.each_grapheme_cluster.to_a.
If a block is given, which is a deprecated form, works the same as each_grapheme_cluster.
Returns the Symbol corresponding to str, creating the symbol if it did not previously exist. See Symbol#id2name.
"Koala".intern #=> :Koala s = 'cat'.to_sym #=> :cat s == :cat #=> true s = '@cat'.to_sym #=> :@cat s == :@cat #=> true
This can also be used to create symbols that cannot be represented using the :xxx notation.
'cat and dog'.to_sym #=> :"cat and dog"
Returns true if str starts with one of the prefixes given. Each of the prefixes should be a String or a Regexp.
"hello".start_with?("hell") #=> true "hello".start_with?(/H/i) #=> true # returns true if one of the prefixes matches. "hello".start_with?("heaven", "hell") #=> true "hello".start_with?("heaven", "paradise") #=> false
Returns a copy of str with leading prefix deleted.
"hello".delete_prefix("hel") #=> "lo" "hello".delete_prefix("llo") #=> "hello"
Deletes leading prefix from str, returning nil if no change was made.
"hello".delete_prefix!("hel") #=> "lo" "hello".delete_prefix!("llo") #=> nil
Changes the encoding to encoding and returns self.
Unicode Normalization—Returns a normalized form of str, using Unicode normalizations NFC, NFD, NFKC, or NFKD. The normalization form used is determined by form, which can be any of the four values :nfc, :nfd, :nfkc, or :nfkd. The default is :nfc.
If the string is not in a Unicode Encoding, then an Exception is raised. In this context, ‘Unicode Encoding’ means any of UTF-8, UTF-16BE/LE, and UTF-32BE/LE, as well as GB18030, UCS_2BE, and UCS_4BE. Anything other than UTF-8 is implemented by converting to UTF-8, which makes it slower than UTF-8.
"a\u0300".unicode_normalize #=> "\u00E0" "a\u0300".unicode_normalize(:nfc) #=> "\u00E0" "\u00E0".unicode_normalize(:nfd) #=> "a\u0300" "\xE0".force_encoding('ISO-8859-1').unicode_normalize(:nfd) #=> Encoding::CompatibilityError raised
Destructive version of String#unicode_normalize, doing Unicode normalization in place.
Checks whether str is in Unicode normalization form form, which can be any of the four values :nfc, :nfd, :nfkc, or :nfkd. The default is :nfc.
If the string is not in a Unicode Encoding, then an Exception is raised. For details, see String#unicode_normalize.
"a\u0300".unicode_normalized? #=> false "a\u0300".unicode_normalized?(:nfd) #=> true "\u00E0".unicode_normalized? #=> true "\u00E0".unicode_normalized?(:nfd) #=> false "\xE0".force_encoding('ISO-8859-1').unicode_normalized? #=> Encoding::CompatibilityError raised
Returns the float truncated to an Integer.
1.2.to_i #=> 1 (-1.2).to_i #=> -1
Note that the limited precision of floating point arithmetic might lead to surprising results:
(0.3 / 0.1).to_i #=> 2 (!)