From: Pierre-Charles David <pcdavid@...>
Date: 2006-03-30T00:02:16+09:00
Subject: Re: strange order of execution

On 3/29/06, James Edward Gray II <james@grayproductions.net> wrote:
> On Mar 29, 2006, at 2:53 AM, vsv wrote:
>
> > I belive Ruby will get implemented in bytecode eventually, at that
> > time
> > 'compile' time evaluation feature will be required; and then, I hope,
> > we'll get 'read' time evaluation too (just dreaming :)
>
> We have it today:
>
>  >> ruby_code = "2 + 2"
> => "2 + 2"
>  >> "2 + 2 = #{eval(ruby_code)}"
> => "2 + 2 = 4"

This is "read-time" evaluation only because currently read-time ==
evaluation time. If Ruby had a compilation phase, string interpolation
would need to be done at execution time. Otherwise a simple program
such as puts "Hello, #{gets}" would require user input during the
compilation phase...

Common Lisp for example has both compile-time evaluation (macros,
(eval-when (:compile) ...)) and read-time evaluation (#., #+ and #-,
the last two being used a little like #ifdef/#ifndef).