class Range # Open an existing class for additions
def by(step) # Define an iterator named by
x = self.begin # Start at one endpoint of the range
if exclude_end? # For ... ranges that exclude the end
while x < self.end # Test with the < operator
yield x
x += step
end
else # Otherwise, for .. ranges that include the end
while x <= self.end # Test with <= operator
yield x
x += step
end
end
end # End of method definition
end # End of class modification
(0..10).by(2) {|x| print x} # Prints "0246810"
(0...10).by(2) {|x| print x} # Prints "02468"
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