Returns the first element, or the first n elements, of the array. If the array is empty, the first form returns nil, and the second form returns an empty array. See also Array#last for the opposite effect.
a = [ "q", "r", "s", "t" ] a.first #=> "q" a.first(2) #=> ["q", "r"]
Returns the last element(s) of self. If the array is empty, the first form returns nil.
See also Array#first for the opposite effect.
a = [ "w", "x", "y", "z" ] a.last #=> "z" a.last(2) #=> ["y", "z"]
Inserts the given values before the element with the given index.
Negative indices count backwards from the end of the array, where -1 is the last element. If a negative index is used, the given values will be inserted after that element, so using an index of -1 will insert the values at the end of the array.
a = %w{ a b c d } a.insert(2, 99) #=> ["a", "b", 99, "c", "d"] a.insert(-2, 1, 2, 3) #=> ["a", "b", 99, "c", 1, 2, 3, "d"]
Returns the number of elements in self. May be zero.
[ 1, 2, 3, 4, 5 ].length #=> 5 [].length #=> 0
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
Returns a string created by converting each element of the array to a string, separated by the given separator. If the separator is nil, it uses current $,. If both the separator and $, are nil, it uses an empty string.
[ "a", "b", "c" ].join #=> "abc" [ "a", "b", "c" ].join("-") #=> "a-b-c"
For nested arrays, join is applied recursively:
[ "a", [1, 2, [:x, :y]], "b" ].join("-") #=> "a-1-2-x-y-b"
Assumes that self is an array of arrays and transposes the rows and columns.
a = [[1,2], [3,4], [5,6]] a.transpose #=> [[1, 3, 5], [2, 4, 6]]
If the length of the subarrays don’t match, an IndexError is raised.
Returns true if the given object is present in self (that is, if any element == object), otherwise returns false.
a = [ "a", "b", "c" ] a.include?("b") #=> true a.include?("z") #=> false
Returns the object in ary with the minimum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.
ary = %w(albatross dog horse) ary.min #=> "albatross" ary.min {|a, b| a.length <=> b.length} #=> "dog"
If the n argument is given, minimum n elements are returned as an array.
ary = %w[albatross dog horse] ary.min(2) #=> ["albatross", "dog"] ary.min(2) {|a, b| a.length <=> b.length } #=> ["dog", "horse"]
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
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 Hash containing implementation-dependent counters inside the VM.
This hash includes information about method/constant cache serials:
{
:global_method_state=>251,
:global_constant_state=>481,
:class_serial=>9029
}
The contents of the hash are implementation specific and may be changed in the future.
This method is only expected to work on C Ruby.
Returns a Digest subclass by name in a thread-safe manner even when on-demand loading is involved.
require 'digest' Digest("MD5") # => Digest::MD5 Digest(:SHA256) # => Digest::SHA256 Digest(:Foo) # => LoadError: library not found for class Digest::Foo -- digest/foo
Mark the object as tainted.
Objects that are marked as tainted will be restricted from various built-in methods. This is to prevent insecure data, such as command-line arguments or strings read from Kernel#gets, from inadvertently compromising the user’s system.
To check whether an object is tainted, use tainted?.
You should only untaint a tainted object if your code has inspected it and determined that it is safe. To do so use untaint.
Returns a string containing a human-readable representation of obj. The default inspect shows the object’s class name, an encoding of the object id, and a list of the instance variables and their values (by calling inspect on each of them). User defined classes should override this method to provide a better representation of obj. When overriding this method, it should return a string whose encoding is compatible with the default external encoding.
[ 1, 2, 3..4, 'five' ].inspect #=> "[1, 2, 3..4, \"five\"]" Time.new.inspect #=> "2008-03-08 19:43:39 +0900" class Foo end Foo.new.inspect #=> "#<Foo:0x0300c868>" class Bar def initialize @bar = 1 end end Bar.new.inspect #=> "#<Bar:0x0300c868 @bar=1>"
Returns true if self is a prime number, else returns false.
Since int is already an Integer, this always returns true.
Returns int truncated (toward zero) to a precision of ndigits decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs trailing zeros.
Returns self when ndigits is zero or positive.
1.truncate #=> 1 1.truncate(2) #=> 1 18.truncate(-1) #=> 10 (-18).truncate(-1) #=> -10
Returns the remainder after dividing int by numeric.
x.remainder(y) means x-y*(x/y).truncate.
5.remainder(3) #=> 2 -5.remainder(3) #=> -2 5.remainder(-3) #=> 2 -5.remainder(-3) #=> -2 5.remainder(1.5) #=> 0.5
See Numeric#divmod.
Returns a string containing the place-value representation of int with radix base (between 2 and 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"
Returns 1.
Returns a complex object which denotes the given rectangular form.
Complex.rectangular(1, 2) #=> (1+2i)
Returns the imaginary part.
Complex(7).imaginary #=> 0 Complex(9, -4).imaginary #=> -4