From: Eli Bendersky <eliben@...>
Date: 2006-05-13T00:09:59+09:00
Subject: Making sense of the various Ruby "eval"s

Hi all,

Unlike other dynamic languages I'm familiar with (Perl, Lisp), Ruby has 
more than one form of 'eval', which is quite confusing for Ruby nubies 
like myself. I'm trying to make some sense of all the possibilities:

- Kernel#eval -

This one I (almost) understand. It behaves like Perl's eval, with the 
difference that it can take a 'binding' which is another Object, or 
Proc. In case of the Object I understand that the code 'eval'ed can 
access the Object's instance vars. But how does that work with a Proc as 
a binding ?

- Object#instance_eval -

Is obj.instance_eval("blah") exactly the same as eval("blah", obj) ? If 
the answer to this question is positive, then the string version of 
instance_eval is clear. But what about its block version ? How does that 
work ? Are the contents of the block just treated as a string ?

- Module#class_eval -

With its synonym module_eval: very similar to Object#instance_eval, just 
that all methods are added to a class and not to an object, right ?

Thanks in advance

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