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