From: Dan Zwell <dzwell@...>
Date: 2007-05-21T04:57:39+09:00
Subject: Re: Emergency help is needed

anoosh wrote:
> Hi all
> I have 2 questions?
> 1)What are the meaning of  symbols(:var) and Instance variables(@x)
> Ruby?(I know Java and C.If it is possible for you  tell me the
> synonyms in these languages,please)
> 
> 2)How can I define my own exception handling in Ruby?
> 
> 

Symbols tend to be used like constants sometimes are in other languages. 
Take this line of java:

jSplitPane.setOrientation(JSplitPane.VERTICAL_SPLIT);

If ruby had this class with these methods, it would probably use symbols 
instead of constants:

jSplitPane.setOrientation(:vertical_split)

Symbols don't have scope--they are not variables. Symbols are unique, 
and they do not contain a value the same way that variables do. I have 
seen them compared to numbers--'4' is unique and its value cannot be 
changed. Also like numbers, you do not need to create them--you can just 
start referencing them.

In C, symbols can be used like (instead of) enums--for constants whose 
value does not actually matter.

Dan