Why doesn't rescue catch Exception by default?

[seth]

From:
http://www.rubycentral.com/book/tut_exceptions.html

— BEGIN
When you need to raise an exception, you can use one of the built-in
Exception classes, or you can create one of your own. If you create your
own, you might want to make it a subclass of StandardError or one of its
children. If you don’t, your exception won’t be caught by default.
— END

My question is why doesn’t it handle the most generalized class,
Exception, by default? What’s the logic behind this?

[seth]

On Jun 21, 2007, at 21:04, Seth wrote:

— END

My question is why doesn’t it handle the most generalized class,
Exception, by default? What’s the logic behind this?

From http://www.zenspider.com/Languages/Ruby/QuickRef.html#34:

Exception
NoMemoryError
ScriptError
LoadError
NotImplementedError
SyntaxError
SignalException
Interrupt
StandardError (default for rescue)
[…]
SystemExit
fatal

You don’t want to rescue any of these other exceptions (besides
StandardError and friends) unless you really know what you’re doing.

Don’t create your own exception classes by subclassing Exception
directly, subclass the closest matching exception class, or subclass
RuntimeError or StandardError.