Returns a new array that is a one-dimensional flattening of self (recursively).
That is, for every element that is an array, extract its elements into the new array.
The optional level argument determines the level of recursion to flatten.
s = [ 1, 2, 3 ] #=> [1, 2, 3] t = [ 4, 5, 6, [7, 8] ] #=> [4, 5, 6, [7, 8]] a = [ s, t, 9, 10 ] #=> [[1, 2, 3], [4, 5, 6, [7, 8]], 9, 10] a.flatten #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] a = [ 1, 2, [3, [4, 5] ] ] a.flatten(1) #=> [1, 2, 3, [4, 5]]
Flattens self in place.
Returns nil if no modifications were made (i.e., the array contains no subarrays.)
The optional level argument determines the level of recursion to flatten.
a = [ 1, 2, [3, [4, 5] ] ] a.flatten! #=> [1, 2, 3, 4, 5] a.flatten! #=> nil a #=> [1, 2, 3, 4, 5] a = [ 1, 2, [3, [4, 5] ] ] a.flatten!(1) #=> [1, 2, 3, [4, 5]]
Returns the number of elements.
If an argument is given, counts the number of elements which equal obj using ==.
If a block is given, counts the number of elements for which the block returns a true value.
ary = [1, 2, 4, 2] ary.count #=> 4 ary.count(2) #=> 2 ary.count {|x| x%2 == 0} #=> 3
Shuffles elements in self in place.
a = [ 1, 2, 3 ] #=> [1, 2, 3] a.shuffle! #=> [2, 3, 1] a #=> [2, 3, 1]
The optional rng argument will be used as the random number generator.
a.shuffle!(random: Random.new(1)) #=> [1, 3, 2]
Returns a new array with elements of self shuffled.
a = [ 1, 2, 3 ] #=> [1, 2, 3] a.shuffle #=> [2, 3, 1] a #=> [1, 2, 3]
The optional rng argument will be used as the random number generator.
a.shuffle(random: Random.new(1)) #=> [1, 3, 2]
Choose a random element or n random elements from the array.
The elements are chosen by using random and unique indices into the array in order to ensure that an element doesn’t repeat itself unless the array already contained duplicate elements.
If the array is empty the first form returns nil and the second form returns an empty array.
a = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] a.sample #=> 7 a.sample(4) #=> [6, 4, 2, 5]
The optional rng argument will be used as the random number generator.
a.sample(random: Random.new(1)) #=> 6 a.sample(4, random: Random.new(1)) #=> [6, 10, 9, 2]
Calls the given block for each element n times or forever if nil is given.
Does nothing if a non-positive number is given or the array is empty.
Returns nil if the loop has finished without getting interrupted.
If no block is given, an Enumerator is returned instead.
a = ["a", "b", "c"] a.cycle {|x| puts x} # print, a, b, c, a, b, c,.. forever. a.cycle(2) {|x| puts x} # print, a, b, c, a, b, c.
When invoked with a block, yield all permutations of length n of the elements of the array, then return the array itself.
If n is not specified, yield all permutations of all elements.
The implementation makes no guarantees about the order in which the permutations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2, 3] a.permutation.to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] a.permutation(1).to_a #=> [[1],[2],[3]] a.permutation(2).to_a #=> [[1,2],[1,3],[2,1],[2,3],[3,1],[3,2]] a.permutation(3).to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]] a.permutation(0).to_a #=> [[]] # one permutation of length 0 a.permutation(4).to_a #=> [] # no permutations of length 4
When invoked with a block, yields all 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 combinations are yielded.
If no block is given, an Enumerator is returned instead.
Examples:
a = [1, 2, 3, 4] a.combination(1).to_a #=> [[1],[2],[3],[4]] a.combination(2).to_a #=> [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]] a.combination(3).to_a #=> [[1,2,3],[1,2,4],[1,3,4],[2,3,4]] a.combination(4).to_a #=> [[1,2,3,4]] a.combination(0).to_a #=> [[]] # one combination of length 0 a.combination(5).to_a #=> [] # no combinations of length 5
Returns an array of all combinations of elements from all arrays.
The length of the returned array is the product of the length of self and the argument arrays.
If given a block, product will yield all combinations and return self instead.
[1,2,3].product([4,5]) #=> [[1,4],[1,5],[2,4],[2,5],[3,4],[3,5]] [1,2].product([1,2]) #=> [[1,1],[1,2],[2,1],[2,2]] [1,2].product([3,4],[5,6]) #=> [[1,3,5],[1,3,6],[1,4,5],[1,4,6], # [2,3,5],[2,3,6],[2,4,5],[2,4,6]] [1,2].product() #=> [[1],[2]] [1,2].product([]) #=> []
Returns first n elements from the array.
If a negative number is given, raises an ArgumentError.
See also Array#drop
a = [1, 2, 3, 4, 5, 0] a.take(3) #=> [1, 2, 3]
Drops first n elements from ary and returns the rest of the elements in an array.
If a negative number is given, raises an ArgumentError.
See also Array#take
a = [1, 2, 3, 4, 5, 0] a.drop(3) #=> [4, 5, 0]
See also Enumerable#any?
See also Enumerable#all?
See also Enumerable#none?
See also Enumerable#one?
Extracts the nested value specified by the sequence of idx objects by calling dig at each step, returning nil if any intermediate step is nil.
a = [[1, [2, 3]]] a.dig(0, 1, 1) #=> 3 a.dig(1, 2, 3) #=> nil a.dig(0, 0, 0) #=> TypeError: Integer does not have #dig method [42, {foo: :bar}].dig(1, :foo) #=> :bar
Returns the sum of elements. For example, [e1, e2, e3].sum returns init + e1 + e2 + e3.
If a block is given, the block is applied to each element before addition.
If ary is empty, it returns init.
[].sum #=> 0 [].sum(0.0) #=> 0.0 [1, 2, 3].sum #=> 6 [3, 5.5].sum #=> 8.5 [2.5, 3.0].sum(0.0) {|e| e * e } #=> 15.25 [Object.new].sum #=> TypeError
The (arithmetic) mean value of an array can be obtained as follows.
mean = ary.sum(0.0) / ary.length
This method can be used for non-numeric objects by explicit init argument.
["a", "b", "c"].sum("") #=> "abc" [[1], [[2]], [3]].sum([]) #=> [1, [2], 3]
However, Array#join and Array#flatten is faster than Array#sum for array of strings and array of arrays.
["a", "b", "c"].join #=> "abc" [[1], [[2]], [3]].flatten(1) #=> [1, [2], 3]
Array#sum method may not respect method redefinition of “+” methods such as Integer#+.
Append — Pushes the given object(s) on to the end of this array. This expression returns the array itself, so several appends may be chained together. See also Array#pop for the opposite effect.
a = [ "a", "b", "c" ] a.push("d", "e", "f") #=> ["a", "b", "c", "d", "e", "f"] [1, 2, 3].push(4).push(5) #=> [1, 2, 3, 4, 5]
Prepends objects to the front of self, moving other elements upwards. See also Array#shift for the opposite effect.
a = [ "b", "c", "d" ] a.unshift("a") #=> ["a", "b", "c", "d"] a.unshift(1, 2) #=> [ 1, 2, "a", "b", "c", "d"]
Returns the number of elements in self. May be zero.
[ 1, 2, 3, 4, 5 ].length #=> 5 [].length #=> 0
Calculates the set of unambiguous abbreviations for the strings in self.
require 'abbrev' %w{ car cone }.abbrev #=> {"car"=>"car", "ca"=>"car", "cone"=>"cone", "con"=>"cone", "co"=>"cone"}
The optional pattern parameter is a pattern or a string. Only input strings that match the pattern or start with the string are included in the output hash.
%w{ fast boat day }.abbrev(/^.a/) #=> {"fast"=>"fast", "fas"=>"fast", "fa"=>"fast", "day"=>"day", "da"=>"day"} Abbrev.abbrev(%w{car box cone}, "ca") #=> {"car"=>"car", "ca"=>"car"}
See also Abbrev.abbrev
provides a unified clone operation, for REXML::XPathParser to use across multiple Object+ types
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.