Returns the result of interpreting ary as an array of [key, value]
pairs.
[[:foo, :bar], [1, 2]].to_h # => {:foo => :bar, 1 => 2}
If a block is given, the results of the block on each element of the array will be used as pairs.
["foo", "bar"].to_h {|s| [s.ord, s]} # => {102=>"foo", 98=>"bar"}
Same as Array#each
, but passes the index
of the element instead of the element itself.
An Enumerator
is returned if no block is given.
a = [ "a", "b", "c" ] a.each_index {|x| print x, " -- " }
produces:
0 -- 1 -- 2 --
Same as Array#each
, but traverses self
in reverse order.
a = [ "a", "b", "c" ] a.reverse_each {|x| print x, " " }
produces:
c b a
Returns the index of the first object in ary
such that the object is ==
to obj
.
If a block is given instead of an argument, returns the index of the first object for which the block returns true
. Returns nil
if no match is found.
See also Array#rindex
.
An Enumerator
is returned if neither a block nor argument is given.
a = [ "a", "b", "c" ] a.index("b") #=> 1 a.index("z") #=> nil a.index {|x| x == "b"} #=> 1
Sorts self
in place using a set of keys generated by mapping the values in self
through the given block.
The result is not guaranteed to be stable. When two keys are equal, the order of the corresponding elements is unpredictable.
If no block is given, an Enumerator
is returned instead.
See also Enumerable#sort_by
.
Deletes every element of self
for which the given block evaluates to false
, and returns self
.
If no block is given, an Enumerator
is returned instead.
a = %w[ a b c d e f ] a.keep_if {|v| v =~ /[aeiou]/ } #=> ["a", "e"] a #=> ["a", "e"]
See also Array#select!
.
Returns an array containing the elements in self
corresponding to the given selector
(s).
The selectors may be either integer indices or ranges.
See also Array#select
.
a = %w{ a b c d e f } a.values_at(1, 3, 5) # => ["b", "d", "f"] a.values_at(1, 3, 5, 7) # => ["b", "d", "f", nil] a.values_at(-1, -2, -2, -7) # => ["f", "e", "e", nil] a.values_at(4..6, 3...6) # => ["e", "f", nil, "d", "e", "f"]
Deletes the element at the specified index
, returning that element, or nil
if the index
is out of range.
See also Array#slice!
a = ["ant", "bat", "cat", "dog"] a.delete_at(2) #=> "cat" a #=> ["ant", "bat", "dog"] a.delete_at(99) #=> nil
Deletes every element of self
for which block evaluates to true
.
The array is changed instantly every time the block is called, not after the iteration is over.
See also Array#reject!
If no block is given, an Enumerator
is returned instead.
scores = [ 97, 42, 75 ] scores.delete_if {|score| score < 80 } #=> [97]
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
Passes elements to the block until the block returns nil
or false
, then stops iterating and returns an array of all prior elements.
If no block is given, an Enumerator
is returned instead.
See also Array#drop_while
a = [1, 2, 3, 4, 5, 0] a.take_while {|i| i < 3} #=> [1, 2]
Drops elements up to, but not including, the first element for which the block returns nil
or false
and returns an array containing the remaining elements.
If no block is given, an Enumerator
is returned instead.
See also Array#take_while
a = [1, 2, 3, 4, 5, 0] a.drop_while {|i| i < 3 } #=> [3, 4, 5, 0]
Creates a string representation of self
.
[ "a", "b", "c" ].to_s #=> "[\"a\", \"b\", \"c\"]"
Return the list of all array-oriented instance variables.
Returns a new string object containing a copy of str.
The optional encoding keyword argument specifies the encoding of the new string. If not specified, the encoding of str is used (or ASCII-8BIT, if str is not specified).
The optional capacity keyword argument specifies the size of the internal buffer. This may improve performance, when the string will be concatenated many times (causing many realloc calls).
Returns a new directory object for the named directory.
The optional encoding keyword argument specifies the encoding of the directory. If not specified, the filesystem encoding is used.
Opens the file named by filename
according to the given mode
and returns a new File
object.
See IO.new
for a description of mode
and opt
.
If a file is being created, permission bits may be given in perm
. These mode and permission bits are platform dependent; on Unix systems, see open(2) and chmod(2) man pages for details.
The new File
object is buffered mode (or non-sync mode), unless filename
is a tty. See IO#flush
, IO#fsync
, IO#fdatasync
, and IO#sync=
about sync mode.
f = File.new("testfile", "r") f = File.new("newfile", "w+") f = File.new("newfile", File::CREAT|File::TRUNC|File::RDWR, 0644)
Creates a new Enumerator
object, which can be used as an Enumerable
.
In the first form, iteration is defined by the given block, in which a “yielder” object, given as block parameter, can be used to yield a value by calling the yield
method (aliased as +<<+):
fib = Enumerator.new do |y| a = b = 1 loop do y << a a, b = b, a + b end end p fib.take(10) # => [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
The optional parameter can be used to specify how to calculate the size in a lazy fashion (see Enumerator#size
). It can either be a value or a callable object.
In the second, deprecated, form, a generated Enumerator
iterates over the given object using the given method with the given arguments passed.
Use of this form is discouraged. Use Kernel#enum_for or Kernel#to_enum instead.
e = Enumerator.new(ObjectSpace, :each_object) #-> ObjectSpace.enum_for(:each_object) e.select { |obj| obj.is_a?(Class) } #=> array of all classes
Construct a new Exception
object, optionally passing in a message.
Create a new SystemExit
exception with the given status and message. Status is true, false, or an integer. If status is not given, true is used.