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|
unless Enumerable.method_defined? :exactly?
module Enumerable
# Checks if exactly n elements meet a certain predicate.
#
# @param n [Fixnum] the number of matches required
# @return [Boolean] true if we get exactly n matches, false otherwise
#
# @example
# [1, 2, 3, 4].exactly?(1) { |n| n > 3 } #=> true
# [1, 2, 3, 4].exactly?(2, &:even?) #=> true
# [1, 1, 3, 3].exactly?(2, &:even?) #=> false
#
# Without a block uses the identify of the elements as default predicate.
# This means that nil and false elements will be ignored.
#
# @example
# [1, false, nil].exactly?(3) #=> false
# [1, false, nil].exactly?(1) #=> true
# [false, nil].exactly?(0) #=> true
# [1, 2, 3].exactly?(3) #=>true
def exactly?(n)
found_count = 0
if block_given?
each do |*o|
if yield(*o)
found_count += 1
return false if found_count > n
end
end
else
each do |o|
if o
found_count += 1
return false if found_count > n
end
end
end
n == found_count
end
end
end
|
