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Ruby On Rails in UA/Code Review, Вопросы по теории программирования/Введение хеши

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2008-06-07 13:43:56	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Введение хеши
	Ниже представлены примеры инициализации хешей empty = Hash.new # => {} empty = {} # => {} numbers = { 'two' => 2, 'eight' => 8} # => {"two"=>2, "eight"=>8} #--- numbers["two"] # => 2 numbers["ten"] = 10 # => 10 numbers # => {"two"=>2, "eight"=>8, "ten"=>10} #--- numbers.keys # => ["two", "eight", "ten"] numbers.values # => [2, 8, 10] numbers.to_a # => [["two", 2], ["eight", 8], ["ten", 10]] #--- motto = "Don't tread on me" flag = { :motto => motto, :picture => "rattlesnake.png"} motto.upcase! flag[:motto] # => "DON'T TREAD ON ME" #--- a = ["Maury", "Momento", "123 Elm St.", "West Covina", "CA"] h = { :first_name => "Maury", :last_name => "Momento", :address => "123 Elm St." :city => "West Covina", :state => "CA" } #--- a = [1, 4, 9, 16] h = { :one_squared => 1, two_squared => 4, three_squared => 9, :four_squared => 16 } #--- class BadIdea def hash 100 end end #--- class StringHolder attr_reader :string def initialize(s) @string = s end def ==(other) @string == other.string end def hash @string.hash end end a = StringHolder.new("The same string.") b = StringHolder.new("The same string.") a == b # => true a.hash # => -1007666862 b.hash # => -1007666862 ```#---
	hash, hash.keys, Hash.new, hash.values, to_a

2008-06-09 17:49:30	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Использование символов как ключей хеша
	people = Hash.new people[:nickname] = 'Matz' people[:language] = 'Japanese' people['last name'.intern] = 'Matsumoto' people[:nickname] # => "Matz" people['nickname'.intern] # => "Matz" #--- 'name'.object_id # => -605973716 'name'.object_id # => -605976356 'name'.object_id # => -605978996 #--- :name.object_id # => 878862 :name.object_id # => 878862 'name'.intern.object_id # => 878862 'name'.intern.object_id # => 878862 #---
	Hash.new

2008-06-02 21:20:03	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Инициализация хешей со значениями по умолчанию
	h = Hash.new h[1] # => nil h['do you have this string?'] # => nil #--- h = Hash.new("nope") h[1] # => "nope" h['do you have this string?'] # => "nope" #--- h = Hash.new { \|hash, key\| (key.respond_to? :to_str) ? "nope" : nil } h[1] # => nil h['do you have this string'] # => "nope" #--- text = 'The rain in Spain falls mainly in the plain.' word_count_hash = Hash.new 0 # => {} text.split(/\W+/).each { \|word\| word_count_hash[word.downcase] += 1 } word_count_hash # => {"rain"=>1, "plain"=>1, "in"=>2, "mainly"=>1, "falls"=>1, # "the"=>2, "spain"=>1} #--- first_letter_hash = Hash.new [] text.split(/\W+/).each { \|word\| first_letter_hash[word[0,1].downcase] << word } first_letter_hash # => {} first_letter_hash["m"] # => ["The", "rain", "in", "Spain", "falls", "mainly", "in", "the", "plain"] #--- first_letter_hash = Hash.new { \|hash, key\| hash[key] = [] } text.split(/\W+/).each { \|word\| first_letter_hash[word[0,1].downcase] << word } first_letter_hash # => {"m"=>["mainly"], "p"=>["plain"], "f"=>["falls"], "r"=>["rain"], # "s"=>["Spain"], "i"=>["in", "in"], "t"=>["The", "the"]} first_letter_hash["m"] # => ["mainly"] #---

2008-06-09 16:31:21	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Удаление элементов из хеша
	h = {} h[1] = 10 h # => {1=>10} h.delete(1) h # => {} #--- h = {} h[5] # => nil h[5] = 10 h[5] # => 10 h[5] = nil h[5] # => nil h.keys # => [5] h.delete(5) h.keys # => [] #--- class Hash def delete_value(value) delete_if { \|k,v\| v == value } end end h = {'apple' => 'green', 'potato' => 'red', 'sun' => 'yellow', 'katydid' => 'green' } h.delete_value('green') h # => {"sun"=>"yellow", "potato"=>"red"} #--- class Hash def remove_hash(other_hash) delete_if { \|k,v\| other_hash[k] == v } end end squares = { 1 => 1, 2 => 4, 3 => 9 } doubles = { 1 => 2, 2 => 4, 3 => 6 } squares.remove_hash(doubles) squares # => {1=>1, 3=>9} #--- h = {} 1.upto(1000) { \|x\| h[x] = x } h.keys.size # => 1000 h.clear h # => {} #---
	delete(1), h.delete(5), h.keys, h.keys.size

2008-06-07 15:40:05	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Печать содержимого хеша
	h = {} h[:name] = "Robert" h[:nickname] = "Bob" h[:age] = 43 h[:email_addresses] = {:home => "bob@example.com", :work => "robert@example.com"} h # => {:email_addresses=>["bob@example.com", "robert@example.com"], # :nickname=>"Bob", :name=>"Robert", :age=>43} puts h # nicknameBobage43nameRobertemail_addresseshomebob@example.comworkrobert@example.com puts h[:email_addresses] # homebob@example.comworkrobert@example.com #--- p h[:email_addresses] # {:home=>"bob@example.com", :work=>"robert@example.com"} #--- p h # {:nickname=>"Bob", :age=>43, :name=>"Robert", :email_addresses=>{:home=>"bob@example.com", :work=>"robert@example.com"}} #--- require 'pp' pp h[:email_addresses] # {:home=>"bob@example.com", :work=>"robert@example.com"} pp h # {:email_addresses=>{:home=>"bob@example.com", :work=>"robert@example.com"}, # :nickname=>"Bob", # :name=>"Robert", # :age=>43} #--- PP::pp(h, $stderr, 50) # {:nickname=>"Bob", # :phone_numbers=> # {:cell=>"(555) 555-5557", # :home=>"(555) 555-5555", # :fax=>"(555) 555-1234", # :work=>"(555) 555-5556"}, # :email_addresses=> # {:home=>"bob@example.com", # :work=>"robert@example.com"}, # :age=>43, # :name=>"Robert"} # => #<IO:0x2c8cc> #--- require 'yaml' puts h.to_yaml # --- # :nickname: Bob # :age: 43 # :name: Robert # :email_addresses: # :home: bob@example.com # :work: robert@example.com #--- h[:email_addresses].each do \|key, val\| puts "#{key} => #{val}" end # home => bob@example.com # work => robert@example.com #---
	hash, pp, to_yaml

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