Weird behaviour of sum in ruby on rails console

Question

Have anyone noticed something like this? Why is it happening?

ruby-1.9.2-p290 :006 > User.count
   (0.4ms)  SELECT COUNT(*) FROM "users" 
 => 102 
ruby-1.9.2-p290 :007 > User.count + 1
   (0.4ms)  SELECT COUNT(*) FROM "users" 
 => 103 
ruby-1.9.2-p290 :008 > User.count+ 1
   (0.4ms)  SELECT COUNT(*) FROM "users" 
 => 103 
ruby-1.9.2-p290 :009 > User.count+1
   (0.4ms)  SELECT COUNT(*) FROM "users" 
 => 103 
ruby-1.9.2-p290 :010 > User.count +1
   (0.5ms)  SELECT COUNT(1) FROM "users" 
 => 102 

Using ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-linux] && Rails 3.1.3

Extra stuff:

ruby-1.9.2-p290 :007 > "ayay".length + 1
 => 5 
ruby-1.9.2-p290 :008 > "ayay".length +1
ArgumentError: wrong number of arguments(1 for 0)
    from (irb):8:in `length'
    ...

Answer 1

This depends on the fact that in Ruby white spaces can be significant. You see different results because Ruby interprets your example in different ways. So

The first:

"ayay".length + 1

is like

"ayay".length.+(1)

And the second:

"ayay".length +1

is like

 "ayay".length(+1)

In this way you can see why Ruby gives an error in the second case.

Regarding the count problem: Ruby interprets the code as:

User.count(+1)

And, as you can see from the generated SQL, there is a difference because +1 is considered the column_name parameter.