From: Mark Sparshatt <msparshatt@...>
Date: 2004-06-26T02:57:00+09:00
Subject: Re: I am confused with Value Type Objects

Sam Sungshik Kong wrote:

>Hello!
>
>In ruby, every object is reference type except for FixNum, NilClass,
>TrueClass, FalseClass.
>Let's consider FixNum only.
>
>According to http://www.rubygarden.org/ruby?GCAndMemoryManagement, FixNum
>takes only 4 bytes (on 32-bit machines).
>Is it true?
>If so, doesn't it have any other information except for the value itself?
>How does ruby know that a FixNum is actually a FixNum instead of a reference
>to an object when it doesn't have any information about the type?
>
>I'm from C# background.
>In C# (actually dotnet framework), values types are structures not just a
>simple value.
>
>Could somebody resolve my confusion?
>
>  
>
Ruby checks the least significant bit of the value. If this is set then 
the value is a direct value such as a fixnum, otherwise it's a reference 
to an object.

When Ruby is constructing a fixnum it left shifts the number one place 
then sets the LSB.

HTH

--
Mark Sparshatt