From: Matt Rogers <mattrogers@...>
Date: 2013-08-03T04:43:58+09:00
Subject: Re: How to use not equal and or

On Fri, Aug 2, 2013 at 1:55 PM, Jesus Avila <lists@ruby-forum.com> wrote:
> ingresa = gets.chomp
>                ingresa = ingresa.downcase
>    if ingresa !="sum"||ingresa !="sub"||ingresa !="mul"||ingresa !="div"
>           puts"You didn't type [Sum,Sub,Mul,Div]"
>           puts"Try again."
>    end
>
> Hi to everyone, I'm a newbie with ruby and I don't know what I doing
> wrong with my code, i want to make a simple calculator just for training
> so what I want to do is to make sure that the user receives a message
> that he didn't type sum, sub, mul or div to start the calculator, the
> other part is finished and working but I don't know how to solve this,
> could you help me with this issue and explain me a little my mistake.
> thank you!
>

I believe your logic is wrong here. You want to check if one of "sum",
"sub", "mul", or "div" is your input, which would indicate that your
logic should be:

if ingresa != "sum" && ingresa != "sub" && ingresa != "mul" && ingresa != "div"
  puts "You didn't type [Sum,Sub,Mul,Div]"
  puts "Try again."
end

You could also take advantage of the #include? method on the Array class:

unless ["sum", "sub", "mul", "div"].include?(ingresa)
  puts "You didn't type [Sum,Sub,Mul,Div]"
  puts "Try again."
end


Hope this helps
--
Matt