From: Robert Klemme <shortcutter@...>
Date: 2008-04-19T21:45:08+09:00
Subject: Re: why doesn't ruby have generics?

On 19.04.2008 14:04, Florian Gilcher wrote:
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> On Apr 19, 2008, at 1:45 PM, Robert Klemme wrote:
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>> On 19.04.2008 12:06, Florian Gilcher wrote:
>>> On Apr 19, 2008, at 11:58 AM, thufir wrote:
>>>> Is it because Ruby is dynamic, or something else?
>>> Why would you bind to a type in a language that doesn't really
>>> care about types? Otherwise, it is easy to implement such
>>> functionality - just build a new kind of array that has to be
>>> constructed with a class. Check for this class on insertion.
>>> I don't see the use, though.
>> That would be a type restricted Array but not a generic Array.  You  
>> cannot have generics in a language whose variables are typeless as  
>> Arlen pointed out.
> 
> Yeah, thats why I was talking about "such functionality". It would  
> serve the same purpose. I was not clear enough about that.

For practical purposes you are probably right.  But strictly speaking 
there is a difference: Java Generics basically are a mechanism for 
automated casting.  This is something else than restricting the type of 
items you put into a collection.  (You can sneak an Integer into a 
List<String> in Java.)

C++ templates are a completely different story - although they "look" 
pretty similar to Java's Generics.  C++ templates allow for generic 
programming which is something different altogether.

In Ruby you can do neither: you cannot cast because variables are 
typeless.  And you cannot have generic algorithms for the same reason.

Kind regards

	robert