Ruby syntax "OR" operator

Question

I have a Rails project and one of my classes has:

def include_stuff?(str)
  str.include? '.' || str.include? '-'
end

Which just give me:

syntax error, unexpected tSTRING_BEG, expecting keyword_end (SyntaxError)
cpf.include? '.' || cpf.include? '-'
                                  ^

I changed the code to:

def include_stuff?(str)
  str.include? '.' or str.include? '-'
end

And no error was thrown.

I tried this too, with success:

def include_stuff?(str)
  str.include?('.') || str.include?('-')
end

Why can't Ruby understand the statement with double pipe, but can understand the statement with the or operator.

I'm using Ruby 2.2.2

Precedence rules, friend. Precedence rules. – Marcelo Camargo Jul 31 '15 at 01:23 — Marcelo Camargo, Jul 31 '15 at 01:23

score 3 · Answer 1 · edited May 23 '17 at 11:51

3

|| and or are not the same in Ruby (see Difference between "or" and || in Ruby?) because of precedence.

So your statement:

str.include? '.' or str.include? '-'

is actually equivalent to:

str.include?('.' || str.include?('-'))

edited May 23 '17 at 11:51

Community

1
1

answered Jul 31 '15 at 01:24

eirikir

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Just continuing the logic. The last statement will become ' str.include?('.') ' right? And thanks for the fast answer, as a newbie in SO, the velocity here are awesome. – Victor Santos Jul 31 '15 at 01:44
@VictorSilvadosSantos Yes, that's correct. As in most languages, if the first argument of a logical disjunction (whether `||` or `or`) is truthy, the second argument isn't even evaluated. – eirikir Jul 31 '15 at 02:04

score 2 · Answer 2 · edited Jun 20 '20 at 09:12

It's to do with operator precedence. or is much lower than ||.

It's trying to parse cpf.include? '.' || cpf.include? '-' as cpf.include?('.' || cpf.include? '-' ) and gets confused as the second include? doesn't have brackets.

http://www.techotopia.com/index.php/Ruby_Operator_Precedence

Note or and || are not the same thing.

see http://devblog.avdi.org/2010/08/02/using-and-and-or-in-ruby/

Conclusion

and and or, despite an apparent similarity to && and ||, have very different roles. and and or are control-flow modifiers like if and unless. When used in this capacity their low precedence is a virtue rather than an annoyance.

As (the invalid) `cpf.include?(('.' || cpf.include?) '-')` then? — user2864740, Jul 31 '15 at 01:24

Ruby syntax "OR" operator

2 Answers2