From: Simon Strandgaard <neoneye@...>
Date: 2004-02-20T20:20:25+09:00
Subject: Re: proposal: let kind_of take more arguments

On Thu, 19 Feb 2004 15:43:05 +0100, Robert Klemme wrote:
> "Simon Strandgaard" <neoneye@adslhome.dk> schrieb im Newsbeitrag
>>
>> def push(choice)
>>   if choice.kind_of?(Zero) == false and choice.kind_of?(One) == false
> 
> Never compare boolean values to get boolean values.  This can lead to
> hideous bugs if the method at hand does not return "true" or "false" -
> especially with languages that have more than one value for either.

Thanks for the warning.  I have actually had a few problems with it
earlier, without realizing this.

 
>> def push(choice)
>>   unless choice.kind_of?(Zero, One)
>>     raise "got #{choice.class}"
> 
> ArgumentError is a good choice here. :-)

I don't have full overview over Ruby's exception hierarchy, but yes
I should use this one here (which I do now).  ;-)
 
>>   end
>>   @choices << choice
>> end
> 
> Why don't you just do
> 
> def push(choice)
>   case choice
>     when Zero, One
>       @choices << choice
>     else
>       raise ArgumentError, "got #{choice.class}"
>   end
> end

a switch statement.. easier to read. 
However I like to do bailout as soon as possible, 
raising ArgumentError this late may make confusion.


 
> or
> 
> def push(choice)
>   raise ArgumentError, "got #{choice.class}" unless [Zero,
> One].map{|cl|choice.kind_of? cl}.any?
>   @choices << choice
> end

Confusion :-)

 

 
> def Object#kind_of_any?( *classes )

Yes thought of this.. which maked me propose this idea.

--
Simon Strandgaard