Integer Range in Ruby

Question

I'm a newbie to Ruby, I have a problem following the Poignant Guide to Ruby:

Does this expression return true?

2005..2009 === 2007

But I don't know why I got this warning message from the following code

wishTraditional.rb:4: warning: integer literal in conditional range

code:

def makTimeLine(year)
if 1984 === year
        "Born."
elsif 2005..2009 === year
        "Sias."
else
        "Sleeping"
end
end
puts makTimeLine(2007)

and the it return Sleeping, which is wrong and should be the Sias

BTW what does the two dots mean? How can I find more information about it?

John Gallagher · Accepted Answer · 2019-01-26 18:39:58Z

11

I think you better use something like that :

elsif (2005..2009).include?(year)

Here is the documentation about Ruby ranges

Update: if you insist on using ===, you should enclose the range in parentheses:

elseif (2005..2009) === year

edited Jan 26, 2019 at 18:39

John Gallagher

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answered Nov 17, 2010 at 11:23

Baramin

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2 Comments

mko Over a year ago

Thanks Baramin, I just figure it out by myself, this is covered in the previous chapter which I skipped. I wouldn't skip chapter again!

Ross R Over a year ago

It is because of operator precedence: === binds before .... stackoverflow.com/a/14258487/1400991

Tim James · Accepted Answer · 2011-04-24 17:34:21Z

3

For independent expressions, yes, you'll need to put range literals in parentheses. But your if/elsif chain would be cleaner as a case statement, which uses === for comparison:

def makTimeLine(year)
  case year
  when 1984
    "Born."
  when 2005..2009
    "Sias."
  else
    "Sleeping"
  end
end

edited Apr 24, 2011 at 17:34

answered Apr 20, 2011 at 18:35

Tim James

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