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enum = Enumerator.new do |yielder| | |
yielder << "a" | |
yielder << "b" | |
yielder << "c" | |
end | |
enum.next # "a" | |
enum.next # "b" | |
enum.next # "c" | |
enum.next # StopIteration: iteration reached an end |
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enum = Enumerator.new do |yielder| | |
yielder << 1 | |
yielder << 2 | |
end | |
loop do | |
puts enum.next | |
end | |
puts 'this will be printed out' |
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array = [1, 2, 3] | |
enum = array.to_enum | |
enum.each {|n| n * 2} # 2 4 6 |
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array = [1, 2, 3] | |
enum = array.to_enum :map | |
enum.each {|n| n * 2} # [2, 4, 6] | |
enum.with_index {|n, index| [index, n ** 2]} # [[0, 1], [1, 4], [2, 9], [3, 16]] |
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array = [1, 2, 3, 4] | |
enum = array.select | |
enum.each {|n| n % 2 == 0} # [2, 4] | |
hash = { one: 1, two: 2 } | |
enum = hash.map | |
enum.each {|_, value| value * 10} # [10, 20] | |
range = 1..10 | |
enum = range.drop_while | |
enum.each {|n| n < 7} # [7, 8, 9, 10] | |
file = File.new 'Rakefile' | |
enum = file.reject | |
enum.each {|line| line.length < 10} # ["#!/usr/bin/env rake\n", | |
"# Add your own tasks in files placed in lib/tasks ending in .rake,\n", | |
...] | |
Struct.new 'Foo', :name, :age | |
foo = Struct::Foo.new 'foo', 42 | |
enum = foo.cycle | |
enum.take 5 # ["foo", 42, "foo", 42, "foo"] |
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enum = 5.times | |
enum.map { [] } # [[], [], [], [], []] | |
enum = 1.upto 10 | |
enum.inject(:+) # 55 | |
enum = 5.downto 0 | |
enum.map {|n| n * 2} # [10, 8, 6, 4, 2, 0] |
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enum = "hello".each_char | |
enum.map &:upcase # ["H", "E", "L", "L", "O"] | |
enum = "abc".each_byte | |
enum.map {|n| n} # [97, 98, 99] | |
enum = "one\ntwo\nthree".each_line | |
enum.map {|line| line.chomp.reverse} # ["eno", "owt", "eerht"] | |
enum = 'a'.upto 'e' | |
enum.grep /[aeiou]/ # ["a", "e"] | |
enum = "one two three".gsub /\b\w+\b/ | |
enum.next # "one" | |
enum.next # "two" | |
enum.next # "three" |
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enum = Enumerator.new do |yielder| | |
n = 0 | |
loop do | |
yielder << n | |
n += 1 | |
end | |
end | |
enum.first 10 # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] |
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enum.select {|n| n % 20 == 0}.first 5 # never returns |
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class Enumerator | |
def lazy_select(&blk) | |
self.class.new do |yielder| | |
each do |n| | |
yielder << n if blk[n] | |
end | |
end | |
end | |
end | |
enum.lazy_select {|n| n % 20 == 0}.first 5 # [0, 20, 40, 60, 80] |
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