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104 lines
2.6 KiB
104 lines
2.6 KiB
require File.expand_path(File.dirname(__FILE__) + '/edgecase')
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class AboutIteration < EdgeCase::Koan
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def test_each_is_a_method_on_arrays
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[].methods.include?("each")
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end
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def test_iterating_with_each
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array = [1, 2, 3]
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sum = 0
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array.each do |item|
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sum += item
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end
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assert_equal __, sum
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end
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def test_each_can_use_curly_brace_blocks_too
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array = [1, 2, 3]
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sum = 0
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array.each { |item|
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sum += item
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}
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assert_equal __, sum
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end
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def test_break_works_with_each_style_iterations
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array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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sum = 0
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array.each { |item|
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break if item > 3
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sum += item
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}
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assert_equal __, sum
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end
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def test_collect_transforms_elements_of_an_array
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array = [1, 2, 3]
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new_array = array.collect { |item| item + 10 }
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assert_equal __, new_array
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# NOTE: 'map' is another name for the 'collect' operation
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another_array = array.map { |item| item + 10 }
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assert_equal __, another_array
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end
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def test_select_selects_certain_items_from_an_array
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array = [1, 2, 3, 4, 5, 6]
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even_numbers = array.select { |item| (item % 2) == 0 }
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assert_equal __, even_numbers
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# NOTE: 'find_all' is another name for the 'select' operation
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more_even_numbers = array.find_all { |item| (item % 2) == 0 }
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assert_equal __, more_even_numbers
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end
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def test_find_locates_the_first_element_matching_a_criteria
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array = ["Jim", "Bill", "Clarence", "Doug", "Eli"]
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assert_equal __, array.find { |item| item.size > 4 }
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end
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def test_inject_will_blow_your_mind
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result = [2, 3, 4].inject(0) { |sum, item| sum + item }
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assert_equal __, result
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result2 = [2, 3, 4].inject(1) { |sum, item| sum * item }
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assert_equal __, result2
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# Extra Credit:
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# Describe in your own words what inject does.
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end
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def test_all_iteration_methods_work_on_any_collection_not_just_arrays
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# Ranges act like a collection
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result = (1..3).map { |item| item + 10 }
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assert_equal __, result
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# Files act like a collection of lines
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File.open("example_file.txt") do |file|
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upcase_lines = file.map { |line| line.strip.upcase }
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assert_equal __, upcase_lines
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end
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# NOTE: You can create your own collections that work with each,
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# map, select, etc.
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end
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# Bonus Question: In the previous koan, we saw the construct:
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#
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# File.open(filename) do |file|
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# # code to read 'file'
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# end
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#
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# Why did we do it that way instead of the following?
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#
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# file = File.open(filename)
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# # code to read 'file'
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#
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# When you get to the "AboutSandwichCode" koan, recheck your answer.
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end
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