Simple way to test if multiple variables have same value, ruby

Question

Is there a simple way of testing that several variables have the same value in ruby?

Something linke this:

if a == b == c == d #does not work
   #Do something because a, b, c and d have the same value
end

Of course it is possible to check each variable against a master to see if they are all true, but that is a bit more syntax and is not as clear.

if a == b && a == c && a == d #does work
    #we have now tested the same thing, but with more syntax.
end

Another reason why you would need something like this is if you actually do work on each variable before you test.

if array1.sort == array2.sort == array3.sort == array4.sort #does not work
    #This is very clear and does not introduce unnecessary variables
end
#VS
tempClutter = array1.sort
if tempClutter == array2.sort && tempClutter == array3.sort && tempClutter == array4.sort #works
   #this works, but introduces temporary variables that makes the code more unclear
end

Shawn Balestracci · Accepted Answer · 2013-05-15 06:50:12Z

24

Throw them all into an array and see if there is only one unique item.

if [a,b,c,d].uniq.length == 1
  #I solve almost every problem by putting things into arrays
end

As sawa points out in the comments .one? fails if they are all false or nil.

edited May 15, 2013 at 6:50

answered May 15, 2013 at 5:55

Shawn Balestracci

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2 Comments

Automatico Over a year ago

Nice. That would definitely be a better way than with the temp variables!

sawa Over a year ago

Note that you cannot use one? if they are to be nil or false.

Community · Accepted Answer · 2017-05-23 10:28:30Z

5

tokland suggested a very nice approach in his comment to a similar question:

module Enumerable
  def all_equal?
    each_cons(2).all? { |x, y| x == y }
  end
end

It's the cleanest way to express this I've seen so far.

edited May 23, 2017 at 10:28

CommunityBot

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answered May 15, 2013 at 6:42

Stefan

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1 Comment

Automatico Over a year ago

I like this solution as well, but without the module extension it is a bit more verbose than Shawn's answer.

pguardiario · Accepted Answer · 2013-05-15 07:05:43Z

3

How about:

[a,b,c,d] == [b,c,d,a]

Really just:

[a,b,c] == [b,c,d]

will do

answered May 15, 2013 at 7:05

pguardiario

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Comments

Arup Rakshit · Accepted Answer · 2013-05-15 08:20:00Z

2

a = [1,1,1]
(a & a).size == 1 #=> true

a = [1,1,2]
(a & a).size == 1 #=> false

edited May 15, 2013 at 8:20

answered May 15, 2013 at 6:55

Arup Rakshit

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3 Comments

Shawn Balestracci Over a year ago

shuffle is not valid, it could end up being in the same order.

Stefan Over a year ago

@Pitri You know that [1,1,2].shuffle returns [1,1,2] sometimes, don't you? ;-)

Arup Rakshit Over a year ago

Yes, you are right partially; so deleted. But shuffle does always,but when duplicate items will be present ,it would fail. :)

Victor Moroz · Accepted Answer · 2013-05-15 19:00:45Z

2

[b, c, d].all?(&a.method(:==))

answered May 15, 2013 at 19:00

Victor Moroz

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