From: Alex Young <alex@...>
Date: 2007-04-08T18:04:06+09:00
Subject: Re: can erb produce erb?

Ken Bloom wrote:
> On Sat, 07 Apr 2007 04:07:16 +0900, Tim Pease wrote:
> 
>> On 4/6/07, talkin ruby <rubytalk.heidmotron@gmail.com> wrote:
>>> just wondering if you could do something like this...
>>>
>>> ERB.new( some_erb_string ).result  #  '<%= result %>'  another erb
>>> template
>>>
>>> so that way the result could be processed by another ERB.new
>>>
>>>
>> You are an evil and twisted individual!  ;)
>>
>> To answer your question, though, sure!  ERb can do that.
>>
>> require 'erb'
>>
>> @blah = '<%= @not_blah %>'
>> ERB.new( "blah <%= @blah %>" ).result    #=>  "blah <%= @not_blah %>"
> 
> If you really want to be evil and twisted, what's the smallest self-
> reproducing erb program you can write that doesn't read its own file.
> 
> The following solution is illegal:
> <%= open(__FILE__){|f| f.read} %>

Drat.  This nearly works:

<%=s=";\"<%=s=\#{s.inspect}\#{s}\"%\>";"<%=s=#{s.inspect}#{s}"%>

The only reason it doesn't is that ERB barfs on '%>' in a string inside 
a <%= %> block, while String#inspect ignores it.  This requires... trickery.

Luckily, we have trickery on hand.  When in doubt, reverse the data:

<%=s=">%\"}esrever.s{#}tcepsni.s{#=s=%<\";";"<%=s=#{s.inspect}#{s.reverse}"%>

That's 77 characters by my count.  77 characters of pure, twisted, evil :-)

-- 
Alex