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Ruby On Rails in UA/Code Review, Вопросы по теории программирования/Инициализация масивов

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2008-06-09 12:28:05	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Инициализация масивов
	Инициализация масива a1 = [] # => [] a2 = [1, 2, 3] # => [1, 2, 3] a3 = [1, 2, 3, 'a', 'b', 'c', nil] # => [1, 2, 3, "a", "b", "c", nil] n1 = 4 n2 = 6 sum_and_difference = [n1, n2, n1+n2, n1-n2] # => [4, 6, 10, -2] #--- %w{1 2 3} # => ["1", "2", "3"] %w{The rat sat on the mat} # => ["The", "rat", "sat", "on", "the", "mat"] #--- увеличиваем размер масива a = [1, 2, 3] # => [1, 2, 3] a << 4.0 # => [1, 2, 3, 4.0] a << 'five' # => [1, 2, 3, 4.0, "five"] #--- a = [1,2,3] # => [1, 2, 3] a << [4, 5, 6] # => [1, 2, 3, [4, 5, 6]] a << a # => [1, 2, 3, [4, 5, 6], [...]] #---вложеные масивы a = [1, 2, 3, [4, 5, 6]] a.size # => 4 a << a # => [1, 2, 3, [4, 5, 6], [...]] a.size # => 5 a[0] # => 1 a[3] # => [4, 5, 6] a[3][0] # => 4 a[3].size # => 3 a[-2] # => [4, 5, 6] a[-1] # => [1, 2, 3, [4, 5, 6], [...]] a[a.size-1] # => [1, 2, 3, [4, 5, 6], [...]] a[-1][-1] # => [1, 2, 3, [4, 5, 6], [...]] a[-1][-1][-1] # => [1, 2, 3, [4, 5, 6], [...]] #---
	array, array cook book

2008-06-10 12:12:51	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Работа с масивами
	[1, 2, 3, 4].each { \|x\| puts x } # 1 # 2 # 3 # 4 #--- [1, 2, 3, 4].collect { \|x\| x ** 2 } # => [1, 4, 9, 16] #--- ['a', 'b', 'c'].each_with_index do \|item, index\| puts "At position #{index}: #{item}" end # At position 0: a # At position 1: b # At position 2: c #--- [1, 2, 3, 4].reverse_each { \|x\| puts x } # 4 # 3 # 2 # 1 #--- array = ['a', 'b', 'c'] array.collect! { \|x\| x.upcase } array # => ["A", "B", "C"] array.map! { \|x\| x.downcase } array # => ["a", "b", "c"] #--- array = ['junk', 'junk', 'junk', 'val1', 'val2'] 3.upto(array.length-1) { \|i\| puts "Value #{array[i]}" } # Value val1 # Value val2 array = ['1', 'a', '2', 'b', '3', 'c'] (0..array.length-1).step(2) do \|i\| puts "Letter #{array[i]} is #{array[i+1]}" end # Letter 1 is a # Letter 2 is b # Letter 3 is c #--- for element in ['a', 'b', 'c'] puts element end # a # b # c for element in (1..3) puts element end # 1 # 2 # 3 #--- array = ['cherry', 'strawberry', 'orange'] for index in (0...array.length) puts "At position #{index}: #{array[index]}" end index = 0 while index < array.length puts "At position #{index}: #{array[index]}" index += 1 end index = 0 until index == array.length puts "At position #{index}: #{array[index]}" index += 1 end # At position 0: cherry # At position 1: strawberry # At position 2: orange #--- array = [1,2,3,4,5] new_array = [] front_index = 0 back_index = array.length-1 while front_index <= back_index new_array << array[front_index] front_index += 1 if front_index <= back_index new_array << array[back_index] back_index -= 1 end end new_array # => [1, 5, 2, 4, 3] #--- class Array def each_from_both_sides front_index = 0 back_index = self.length-1 while front_index <= back_index yield self[front_index] front_index += 1 if front_index <= back_index yield self[back_index] back_index -= 1 end end end end new_array = [] [1,2,3,4,5].each_from_both_sides { \|x\| new_array << x } new_array # => [1, 5, 2, 4, 3] #--- class Array def collect_from_both_sides new_array = [] each_from_both_sides { \|x\| new_array << yield(x) } return new_array end end ["ham", "eggs", "and"].collect_from_both_sides { \|x\| x.capitalize } # => ["Ham", "And", "Eggs"] #---
	collect, collect!, each, map!, reverce_each, Работа с масивами

2008-06-09 16:42:41	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Извлечение значений из масивов, запись временных переменных
	a = 1 b = 2 a, b = b, a a # => 2 b # => 1 #--- a, b, c = :red, :green, :blue c, a, b = a, b, c a # => :green b # => :blue c # => :red #--- array = [:red, :green, :blue] c, a, b = array a # => :green b # => :blue c # => :red #--- a, b, *c = [12, 14, 178, 89, 90] a # => 12 b # => 14 c # => [178, 89, 90] #--- a, b = 1, 2 x = a a = b b = x #--- a, b = 5, 10 a, b = b/a, a-1 # => [2, 4] a, b, c = 'A', 'B', 'C' a, b, c = [a, b], { b => c }, a a # => ["A", "B"] b # => {"B"=>"C"} c # => "A" #--- a, b = 1, 2 a, b = b a # => 2 b # => nil #--- a, b = rand(1000), rand(1000) # => [595, 742] a = a ^ b # => 181 b = b ^ a # => 595 a = a ^ b # => 742 [a, b] # => [742, 595] #---
	array

2008-06-07 23:43:54	Ответить
Ruslan Voloshin Адрес: odessa Сообщений: 1199 Регистр: 2007-03-13 его блог 40 сообщ.	Удаление дубликатов из масивов
	survey_results = [1, 2, 7, 1, 1, 5, 2, 5, 1] distinct_answers = survey_results.uniq # => [1, 2, 7, 5] survey_results.uniq! survey_results # => [1, 2, 7, 5] #--- require 'set' survey_results = [1, 2, 7, 1, 1, 5, 2, 5, 1] distinct_answers = survey_results.to_set # => #<Set: {5, 1, 7, 2}> games = [["Alice", "Bob"], ["Carol", "Ted"], ["Alice", "Mallory"], ["Ted", "Bob"]] players = games.inject(Set.new) { \|set, game\| game.each { \|p\| set << p }; set } # => #<Set: {"Alice", "Mallory", "Ted", "Carol", "Bob"}> players << "Ted" # => #<Set: {"Alice", "Mallory", "Ted", "Carol", "Bob"}> #--- class OrderedSet < Set def initialize @hash \|\|= OrderedHash.new end end #--- a = [1, 2, nil, 3, 3, nil, nil, nil, 5] a.compact # => [1, 2, 3, 3, 5] a.delete(3) a # => [1, 2, nil, nil, nil, nil, 5] ```#---
	array.compact, attay.inject, удаление дубликатов

2008-07-18 14:49:42	Ответить
Galeta Pavel Адрес: Kiev Сообщений: 3 Регистр: 2007-07-19 его блог 0 сообщ.	RE: Инициализация масивов
	Только не забываем что capitalize, downcase и upcase НЕ РАБОТАЮТ с кириллицей!
	capitalize, downcase, upcase, кириллица

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