From: Robert Klemme <shortcutter@...>
Date: 2010-11-02T16:22:02+09:00
Subject: Re: Implicitly convert Symbols to Strings?

On Tue, Nov 2, 2010 at 3:36 AM, John Mair <jrmair@gmail.com> wrote:
> Is there a good reason why Symbols are not implictly converted to
> Strings ?
>
> The following does not work for example:
>
>    eval(:self) #=> Error: can't convert Symbol to String

But you can do eval(x.to_s) for any type of x - including Symbols.

> But if we do the following:
>
>    class Symbol
>      def to_str
>        to_s
>      end
>    end
>
> Then it works:
>
>    eval(:self) #=> main
>
> In my opinion this implicit conversion should happen and would be
> useful in some circumstances. Why isn't this supported out of the box?

Because Symbols are not Strings.  For example, assume you use a Symbol
in a place where a String is expected.  The String is manipulated but
the changes go away because the modification was on an automatically
created temporary String and is lost without you noticing.  Method
#to_str is really reserved only for classes that are String compatible
- and immutable Symbols aren't.

irb(main):001:0> ObjectSpace.each_object(Module){|m| p m if
m.instance_methods.include?(:to_str)}
NameError::message
String
=> 398

Take another example:

irb(main):002:0> ObjectSpace.each_object(Module){|m| p m if
m.instance_methods.include?(:to_int)}
Complex
Rational
Bignum
Float
Fixnum
Integer
Numeric
=> 398
irb(main):003:0> ObjectSpace.each_object(Module){|m| p m if
m.instance_methods.include?(:to_i)}
Complex
Rational
Process::Status
Time
File
ARGF.class
IO
Bignum
Float
Fixnum
Integer
String
NilClass
=> 398

Kind regards

robert

-- 
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