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I am trying to understand string concatenation.

Why doesn't the fourth line give the same result as the second one?

counter = 0
"#{counter+1}. test" gives "1. test"
counter = 0
"#{++counter}. test" gives "0. test"
the Tin Man
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ssinganamalla
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    same result or different results, moreover ruby does not support the `++` operator – bjhaid Feb 28 '14 at 03:18
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    See this answer as well: http://stackoverflow.com/questions/5680587/whats-the-point-of-unary-plus-operator-in-ruby – Zach Kemp Feb 28 '14 at 03:20
  • Just asked a question going into a little more detail on this that I'm curious about: http://stackoverflow.com/questions/22085607/ruby-unary-operator-behavior It also illustrates how you can redefine the unary `+` operator which might shed a little light on why it exists. – JKillian Feb 28 '14 at 03:30

6 Answers6

3

++ just looks like the increment operator. It's actually two unary + operators, so it's just the same as plain old counter

JKillian
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Because, ++ is not an operator for Ruby like C or Java.

the Tin Man
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Masudul
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There is no ++ operator in Ruby. What ++counter says is "give me the positive result of the positive result of 0" which is 0.

Zach Kemp
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++ is not an operator in Ruby. If you want to use a pre-increment operator then use:

counter += 1
the Tin Man
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Ganesh Kunwar
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In Ruby, ++x or --x will do nothing! In fact, they behave as multiple unary prefix operators: -x == ---x == -----x == ...... or +x == +++x == +++++x == ......

To increment a number, simply write x += 1.

To decrement a number, simply write x -= 1.

Proof :

x = 1
+x == ++++++x # => true
-x == -----x # => true
x # => 1 # value of x doesn't change.
Arup Rakshit
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In C 

++counter //Pre Increment 
counter++// Post Incremet

But In Ruby ++ has no existence ,

So if you want to increment a variable then you have to simply write

counter = counter + 1

In your case you have to write just

 "#{counter = counter + 1}. test" gives "1. test"

And will increment the value counter by 1

Arjun
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