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Ruby Ruby Operators and Control Structures Logical Operators The Or (||) Operator

Jason Chow
Jason Chow
4,428 Points
Posted by Jason Chow
Jason Chow
4,428 Points

Ruby Operators and Control Structures (valid_command?)

def valid_command?(command) if (command = gets.chomp.downcase) && (command = gets.chomp.upcase) return true end end

please help.

ruby.rb 
def valid_command?(command)
  if (command = gets.chomp.downcase) && (command = gets.chomp.upcase)
    return true
  end
end

2 Answers

Galen Cook
Galen Cook
2,463 Points
Galen Cook
Galen Cook
2,463 Points

You didn't really ask a question, but I believe your problem is that you are using the single equals sign (which sets a variable's value) rather than the double equals sign (which compares two values).

Replace your = with ==

david carter
david carter
9,677 Points
david carter
david carter
9,677 Points

yeah, without a question it's not that clear what you need. here are some things i see about the code:

  • right now, it will always return true, no matter what you supply as an argument. The reason is that both statements
command = gets.chomp.downcase

and

command = gets.chomp.upcase

are going to be coerced into truthy statements. and truthy && truthy is true in ruby. even if you don't provide any input and just hit Enter when prompted for input (once for each gets.chomp call), the statement:

"" && ""

evaluates to

""

which is truthy so it will return true. You're basically just reassigning the variable command twice to whatever comes in through std.in..

  • It's not clear what a valid command is. even if you replace the single equals with double equals, I can only see the statement evaluating to true if there are no letters involved.. just numbers or punctuation.. how could any string downcased be equivalent to the same string upcased? are commands only valid if they are non-alphabetic?

  • Lastly, you should have either an else return false or put a false statement at the end of the method so that the method always will, as the question mark implies, evaluate to a boolean value.

Hope that helps

  • If i knew what you were trying to accomplish with this code, I might be able to provide more constructive feedback. IF valid commands are only those that return true when the command.upcase is equal to the command.downcase, the following code will work:
def valid_command?
  cmd = gets.chomp
  cmd.downcase == cmd.upcase
end