From: Sam Duncan <sduncan@...>
Date: 2010-12-14T11:03:58+09:00
Subject: Re: String or string

ruby-1.9.2-p0 > u2 = "foo"
  => "foo"
ruby-1.9.2-p0 > puts "blah" unless ["force", "spells"].include?(u2)
blah
  => nil
ruby-1.9.2-p0 > u2 = "force"
  => "force"
ruby-1.9.2-p0 > puts "blah" unless ["force", "spells"].include?(u2)
  => nil
ruby-1.9.2-p0 > u2 = "spells"
  => "spells"
ruby-1.9.2-p0 > puts "blah" unless ["force", "spells"].include?(u2)
  => nil


On 14/12/10 14:58, Garrison Taylor wrote:
> I want it to puts blah if u2 isn't force or spells.
>
> Scratch.mit.edu. Go there!
>
> -gbear605
>
> On Dec 13, 2010, at 7:57 PM, Ross Harvey<chaos@ross.aero>  wrote:
>
>    
>> Same problem, though. That's the same thing as
>>
>>     if (u2 != "...") || true
>>
>> Which, of course, is the same thing as "if true".
>>
>> Did you mean:
>>
>>    if u2 != "force"&&  u2 != "spells"
>>
>> ...perhaps?
>>
>> On Mon, Dec 13, 2010 at 3:27 PM, Garrison Taylor
>> <garrisontaylor@gmail.com>  wrote:
>>      
>>> When I typed it I wasn't looking at it, it was actually
>>>
>>> u2 = gets.chomp
>>>   If u2 != "force" || "spells"
>>>   Puts "blah"
>>>
>>> Scratch.mit.edu. Go there!
>>>
>>> -gbear605
>>>
>>> On Dec 13, 2010, at 6:09 PM, Josh Cheek<josh.cheek@gmail.com>  wrote:
>>>
>>>        
>>>> On Mon, Dec 13, 2010 at 4:53 PM, Garrison Taylor
>>>> <garrisontaylor@gmail.com>wrote:
>>>>
>>>>          
>>>>> I am doing something where I do
>>>>> If "force" || "spells"
>>>>> Puts "blah"
>>>>>
>>>>>
>>>>>
>>>>> When I use it it gives a warning about comparing strings, what's happening
>>>>> and how do I fix it?
>>>>>
>>>>> Scratch.mit.edu. Go there!
>>>>>
>>>>> -gbear605
>>>>>
>>>>>            
>>>> || is a boolean method meaning "or". It is concerned with the truthiness and
>>>> falsiness of its parameters. The set of falsy objects is { false , nil },
>>>> everything else is truthy. That means that strings are truthy, so when you
>>>> say "force" || "spells" it looks at "force", sees it isn't false and it
>>>> isn't nil, and so is considered true. Every time.
>>>>
>>>> So "force" || "spells" will always return "force", a truthy value, to the if
>>>> statement. Thus the if statement will always execute.
>>>>
>>>> if "force" || "spells"
>>>>   puts "blah"
>>>> end
>>>>
>>>> is the same as
>>>>
>>>> if "force"
>>>>   puts "blah"
>>>> end
>>>>
>>>> is the same as
>>>>
>>>> if true
>>>>   puts "blah"
>>>> end
>>>>
>>>> is the same as
>>>>
>>>> puts "blah"
>>>>
>>>>
>>>>
>>>> That is probably not what you wanted, so it warns you of the issue.
>>>>          
>>>
>>>        
>>      
>