Returns the object in enum that gives the maximum value from the given block.
If no block is given, an enumerator is returned instead.
a = %w(albatross dog horse) a.max_by { |x| x.length } #=> "albatross"
If the n
argument is given, maximum n
elements are returned as an array. These n
elements are sorted by the value from the given block, in descending order.
a = %w[albatross dog horse] a.max_by(2) {|x| x.length } #=> ["albatross", "horse"]
enum.max_by(n) can be used to implement weighted random sampling. Following example implements and use Enumerable#wsample.
module Enumerable # weighted random sampling. # # Pavlos S. Efraimidis, Paul G. Spirakis # Weighted random sampling with a reservoir # Information Processing Letters # Volume 97, Issue 5 (16 March 2006) def wsample(n) self.max_by(n) {|v| rand ** (1.0/yield(v)) } end end e = (-20..20).to_a*10000 a = e.wsample(20000) {|x| Math.exp(-(x/5.0)**2) # normal distribution } # a is 20000 samples from e. p a.length #=> 20000 h = a.group_by {|x| x } -10.upto(10) {|x| puts "*" * (h[x].length/30.0).to_i if h[x] } #=> * # *** # ****** # *********** # ****************** # ***************************** # ***************************************** # **************************************************** # *************************************************************** # ******************************************************************** # *********************************************************************** # *********************************************************************** # ************************************************************** # **************************************************** # *************************************** # *************************** # ****************** # *********** # ******* # *** # *
Adds aProc as a finalizer, to be called after obj was destroyed. The object ID of the obj will be passed as an argument to aProc. If aProc is a lambda or method, make sure it can be called with a single argument.
Removes all finalizers for obj.
Adds a post-installs hook that will be passed a Gem::DependencyInstaller
and a list of installed specifications when Gem::DependencyInstaller#install
is complete
Is this handler a streaming handler?
Sends a EXAMINE command to select a mailbox
so that messages in the mailbox
can be accessed. Behaves the same as select()
, except that the selected mailbox
is identified as read-only.
A Net::IMAP::NoResponseError
is raised if the mailbox does not exist or is for some reason non-examinable.
Returns true
if the given instance variable is defined in obj. String
arguments are converted to symbols.
class Fred def initialize(p1, p2) @a, @b = p1, p2 end end fred = Fred.new('cat', 99) fred.instance_variable_defined?(:@a) #=> true fred.instance_variable_defined?("@b") #=> true fred.instance_variable_defined?("@c") #=> false
Defines a singleton method in the receiver. The method parameter can be a Proc
, a Method
or an UnboundMethod
object. If a block is specified, it is used as the method body. If a block or a method has parameters, they’re used as method parameters.
class A class << self def class_name to_s end end end A.define_singleton_method(:who_am_i) do "I am: #{class_name}" end A.who_am_i # ==> "I am: A" guy = "Bob" guy.define_singleton_method(:hello) { "#{self}: Hello there!" } guy.hello #=> "Bob: Hello there!" chris = "Chris" chris.define_singleton_method(:greet) {|greeting| "#{greeting}, I'm Chris!" } chris.greet("Hi") #=> "Hi, I'm Chris!"
DO NOT USE THIS DIRECTLY.
Hook method to return whether the obj can respond to id method or not.
When the method name parameter is given as a string, the string is converted to a symbol.
See respond_to?
, and the example of BasicObject
.
Invoked as a callback whenever a singleton method is added to the receiver.
module Chatty def Chatty.singleton_method_added(id) puts "Adding #{id.id2name}" end def self.one() end def two() end def Chatty.three() end end
produces:
Adding singleton_method_added Adding one Adding three
Checks for a method provided by this the delegate object by forwarding the call through _getobj_.
Specifies Emacs editing mode. The default is this mode. See the manual of GNU Readline
for details of Emacs editing mode.
Raises NotImplementedError
if the using readline library does not support.
Returns true if emacs mode is active. Returns false if not.
Raises NotImplementedError
if the using readline library does not support.