From: Yukihiro Matsumoto <matz@...>
Date: 2006-10-16T10:51:20+09:00
Subject: Re: Symbol < String in Ruby > 1.8

Hi

In message "Re: Symbol < String in Ruby > 1.8"
    on Sun, 15 Oct 2006 22:26:11 +0900, dblack@wobblini.net writes:

|I'm wondering if someone could summarize for me the rationale for
|making Symbol a subclass of String in 1.9.  I understand that symbols
|and strings both represent text, and have certain characteristics in
|common, but I always thought of symbols as an internally used data
|type that Ruby exposes, essentially unchanged, for our use.  It's hard
|to adjust to thinking of them as string descendants.

  * in preparation M17N enhancement, a symbol should contain encoding
    information as well as strings.  it was most natural to inherit
    String class to accomplish this.

  * methods like instance_variables, methods etc. should return
    Symbols, not mere Strings, because they are exposed internal
    names.  For better migration path, Symbols should act more like
    strings.

  * so, Symbols are now immutable, interned strings, with some
    performance enhancement.

  * Symbol being a subclass of String follows Smalltalk design.

  * as a side effect, option hash tables (like the ones in Rails) work
    better with strings, without making any hacked hash table.

							matz.