Втора лекция от курса във ФМИ.

1. speaker { [“Stefan”, “Kanev”].join(“ “) }
speaker { “Nikolay” + “ “ + “Bachiyski” }
on_date { @lecture_date || “13‐10‐2008” }
2. Функционални
закачки

2. speaker { [“Stefan”, “Kanev”].join(“ “) }
speaker { “Nikolay” + “ “ + “Bachiyski” }
on_date { @lecture_date || “13‐10‐2008” }
2. Функционални
закачки

4. Хиперкуб

5. 3. 1415926535 8979323846 2643383279 5028841971 6939937510
5820974944 5923078164 0628620899 8628034825 3421170679
8214808651 3282306647 0938446095 5058223172 5359408128
4811174502 8410270193 8521105559 6446229489 5493038196
4428810975 6659334461 2847564823 3786783165 2712019091
4564856692 3460348610 4543266482 1339360726 0249141273
7245870066 0631558817 4881520920 9628292540 9171536436
7892590360 0113305305 4882046652 1384146951 9415116094
3305727036 5759591953 0921861173 8193261179 3105118548
0744623799 6274956735 1885752724 8912279381 8301194912
9833673362 4406566430 8602139494 6395224737 1907021798
6094370277 0539217176 2931767523 8467481846 7669405132
0005681271 4526356082 7785771342 7577896091 7363717872
1468440901 2249534301 4654958537 1050792279 6892589235
4201995611 2129021960 8640344181 5981362977 4771309960
5187072113 4999999837 2978049951 0597317328 1609631859
5024459455 3469083026 4252230825 3344685035 2619311881

9. Domain
Specific
Language

10. mind.refresh

11. 3.14
1_729
quot;Who is John Galt?quot;
[18, :f, quot;Sofiaquot;]
{:jazz => [quot;Thelonious Monkquot;, quot;Bill Evansquot;],
:baroque => [quot;J.S. Bachquot;, quot;Henry Purcellquot;],
:classical => [quot;L.V. Beethovenquot;, quot;W.A. Mozartquot;] }

12. if hungry?
eat
else
sleep until hungry?
end
work until job.done?
write_code(:ruby) while me.unhappy?
eat(food) if hungry?
write_code unless tired?

13. функции

14. функционално
програмиране

18. приема неща
връща неща

19. приема неща
връща неща
Обекти

21. order, change = use_machine(number, money)

22. Неща
order, change = use_machine(number, money)
coffee, change = use_machine(42, 1.50)

24. cup, cash = order(quot;Cappuccinoquot;, 3) do |pref|
pref.make_short
pref.add_sugar 2
pref.add_extra :cream
end

25. приема неща
връща неща

26. приема неща
приема инструкции
връща неща

27. приема неща
приема инструкции
връща неща
Код

28. cup, cash = order(quot;Cappuccinoquot;, 3) do |pref|
pref.make_short
pref.add_sugar 2
pref.add_extra :cream
end

29. >> numbers = [2, 3, 5, 7]
>> numbers.map { |x| x ** 2 }
[4, 9, 25, 49]
>> numbers.select { |x| x > 4 }
[5, 7]

30. извикване do |аргументи|
код
end
извикване { |аргументи| код }

31. File.open(quot;spendingsquot;).each_line do |line|
next unless well_formed?(line)
date, category, amount = line.split
category_sum[category] += amount.to_i
end
points.all? { |x,y| saved.include? [y,x] }

32. Щипки
Улей
points.all? { |x,y| saved.include? [y,x] }
Итератор Блок / Корутина

35. Пич, извикай
корутината

36. def twice
yield
yield
end
twice { puts “Ruby rocks!” }

37. accumulate

38. def accum(start, items)
result, items = start, items.dup
yield(result, items.pop) until items.empty?
result
end
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
puts accum(0, numbers) { |a, b| a + b }
puts accum(1, numbers) { |a, b| a * b }

39. def with_primes(max)
2.upto(max) do |n|
yield n unless (2...n).any? { |c| n % c == 0 }
end
end
with_primes(10) { |x| puts x }

40. 2.upto(10) do |n|

41. (2..10)
(2…10)

42. any?
all?

43. students.any? { |s| s.cheated? }
numbers.all? { |x| x % 2 == 0 }

44. def with_primes(max)
2.upto(max) do |n|
yield n unless (2...n).any? { |c| n % c == 0 }
end
end
with_primes(10) { |x| puts x }

45. return

46. def magic_roots(numbers)
numbers.map do |number|
return number ** 0.5 if number < 0
(‐number) ** 0.5
end
end
magic_roots([100, ‐25, ‐9, 16])

47. def
return
end

48. next
break

49. n, found = 1, 0
while true
n += 1
next unless (2...n).any? { |a| n % a == 0 }
found += 1
puts quot;#{n} squared is #{n * n}quot;
break if found >= 50
end

50. lucky = []
users.each do |user|
next unless user.submitted_homework?
lucky << user
break if lucky.size >= 5
end

51. next(arg)
break(arg)

52. item = items.first_item
found = until item.nil?
break item if item.nice? and item.shiny?
item = item.successor
end

53. def magic_roots(numbers)
numbers.map do |number|
next number ** 0.5 if number < 0
(‐number) ** 0.5
end
end
magic_roots([100, ‐25, ‐9, 16])

54. Щипки
Улей
points.all? { |x,y| saved.include? [y,x] }
Итератор Блок / Корутина

55. next
излез от блока в итератора
break
излез от итератора

56. lucky = []
users.each do |user|
next unless user.submitted_homework?
lucky << user
break if lucky.size >= 5
end

57. Enumerable
Array
Hash

58. collect
select
inject

59. 001:0> numbers = [1, 2, 3, 4, 5, 6, 7]
=> [1, 2, 3, 4, 5, 6, 7]
002:0> numbers.collect { |n| n ** 2 }
=> [1, 4, 9, 16, 25, 36, 49]
003:0> numbers.select { |n| n % 2 == 0 }
=> [2, 4, 6]
004:0> numbers.inject { |a, b| a + b }
=> 28

60. emails = []
users.each do |user|
emails << user.email if user.active?
end
return emails
users.select { |u| u.active? }.map { |u| u.email }

61. alias :collect, :map
alias :select, :find_all

62. 001:0> people = [quot;Coltranequot;, quot;Monkquot;, quot;Davisquot;, quot;Evansquot;]
002:0> people.all? { |x| x =~ /^[A‐Z][a‐z]+$/ }
=> true
003:0> people.any? { |name| name.include? 'trane' }
=> true
004:0> people.sort
=> [quot;Coltranequot;, quot;Davisquot;, quot;Evansquot;, quot;Monkquot;]
005:0> people.sort { |a, b| a.size <=> b.size }
=> [quot;Monkquot;, quot;Evansquot;, quot;Davisquot;, quot;Coltranequot;]
006:0> people.sort_by { |name| name.size }
=> [quot;Monkquot;, quot;Evansquot;, quot;Davisquot;, quot;Coltranequot;]
007:0> people.each_with_index { |n, i| puts quot;#{i}. #{n}quot; }
0. Coltrane
1. Monk
2. Davis
3. Evans
008:0> people.detect { |name| name.include? quot;squot; }
=> quot;Davis“
009:0> people.zip([quot;Johnquot;, quot;Theloniousquot;, quot;Milesquot;, quot;Billquot;])
=> [[quot;Coltranequot;, quot;Johnquot;], [quot;Monkquot;, quot;Theloniousquot;], [quot;Davisquot;,
quot;Milesquot;], [quot;Evansquot;, quot;Billquot;]]

63. collect!
select!

65. :symbol

66. symbol != char

67. Symbol.similar_to String

68. {
:host => quot;fmi.rails‐bg.netquot;,
:port => 3306,
:username => quot;websitequot;,
:password => quot;gouldquot;,
:database => quot;websitequot;,
}

69. wazup?!!!?!??1:!!??
def wazup?(a)
puts quot;#{a} dat!quot;
end

70. def greet(name = quot;Unknownquot;)
puts quot;Greetings, #{name}quot;
end
greet
greet quot;Rubyquot;

71. connect :db, :host => quot;172.0.0.1quot;, :port => 3306
connect(:db, {:host => quot;172.0.0.1quot;, :port => 3306})
def connect(what, options = {})

72. form_for(url, html_options)
form_for {:action => quot;showquot;, :id => 1}, :class => quot;horizontalquot;
form_for do
:action => quot;showquot;, :id => 1
end, :class => quot;horizontalquot;

73. 001:0> hash, string = {quot;Johnquot; => quot;Coltranequot;,
quot;Eddiequot; => quot;Vedderquot;}, quot;larnodiquot;
002:0> puts hash.to_s
JohnColtraneEddieVedder
003:0> puts hash.inspect
{quot;Johnquot;=>quot;Coltranequot;, quot;Eddiequot;=>quot;Vedderquot;}
004:0> puts string.to_s
lar
odi
005:0> puts string.inspect
quot;larodiquot;

74. to_s
inspect

75. p foo
quot;It is: %pquot; % foo

82. lambda

83. square = lambda { |x| x ** 2 }
puts square(7) # Не работи
puts square.call(7)
puts square[7]

84. seek = lambda do |needle, haystack|
haystack.each do |item|
return true if item.equal?(needle)
end
false
end

85. square = ‐> (x) { x ** 2 }
1.9

86. Proc.new

87. root = Proc.new { |x| x ** 0.5 }
positivep = Proc.new { |x| x > 0 }
puts root[x] if positivep[x]

88. def my_map(list, operation)
result = []
list.each do |item|
result << operation[item]
end
result
end
p my_map([2, 3, 5, 7], Proc.new { |x| x ** 2})

89. def my_map(list, operation)
result = []
list.each do |item|
result << yield(item)
end
result
end
p my_map([2, 3, 5, 7]) { |x| x ** 2}

90. def my_map(list, operation)
result = []
list.each do |item|
result << yield(item)
end
result
end
operation = Proc.new { |x| x ** 2 }
p my_map([2, 3, 5, 7]) ... ???

91. proc → block

92. def my_map(list, operation)
result = []
list.each do |item|
result << yield(item)
end
result
end
operation = Proc.new { |x| x ** 2 }
p my_map([2, 3, 5, 7], &operation)

93. block → proc

94. def my_map(list, &operation)
result = []
list.each do |item|
result << operation[item]
end
result
end
p my_map([2, 3, 5, 7]) { |x| x ** 2 }

95. block_given?

96. def can_has_block?
return block_given?
end
puts can_has_block? # false
puts can_has_block? { “plz } # true

97. def my_proc(&block)
block
end
square = my_proc { |x| x ** 2 }
puts square.call(7)
puts square[42]

98. (‐>_{_%_})[quot;(‐>_{_%%_})[%p]quot;]

99. def raise_to_power(numbers, power)
numbers.map { |x| x ** power }
end
p raise_to_power([2, 3, 5, 7], 3)

100. def raise_to_power(numbers, power)
numbers.map { |x| x ** power }
end
p raise_to_power([2, 3, 5, 7], 3)

101. def make_stamp(owner)
time = Time.now
lambda do |thing|
quot;#{time}: #{thing} is owned by #{owner}quot;
end
end
sony = make_stamp(quot;Sonyquot;)
puts sony[quot;Playstationquot;]
sleep 1
microsoft = make_stamp(quot;Microsoftquot;)
puts microsoft[quot;X‐boxquot;]
puts sony[quot;Playstationquot;]

102. Mon Oct 13 16:37:22 +0300 2008: Playstation
is owned by Sony
Mon Oct 13 16:37:23 +0300 2008: X‐box is
owned by Microsoft
Mon Oct 13 16:37:22 +0300 2008: Playstation
is owned by Sony

103. def cuckoo
n = 0
tick = lambda { n += 1 }
tack = lambda { puts n }
return tick, tack
end
one, two = cuckoo
two[] # 0
one[]
two[] # 1
one[]
three, four = cuckoo
four[] # 0
two[] # 2

104. can_haz_keushunz?