From: Stefan Kaes <skaes@...>
Date: 2005-03-16T15:01:55+09:00
Subject: Re: eval/binding question

Yukihiro Matsumoto wrote:

>Hi,
>
>In message "Re: eval/binding question"
>    on Wed, 16 Mar 2005 02:45:41 +0900, Stefan Kaes <skaes@gmx.net> writes:
>
>|In the real environment, the names of the locally assigned variables can 
>|not be determined in advance, of course.
>
>I'm sorry to say you can't pre-compile eRB allowing local variable set
>not determined in advance.  I know allowing this will make your
>program 25% faster, but this also would make any other programs
>slower.
>  
>
I fail to see why it would make other code slower. I am convinced with a 
proper compiler implementation there would'nt be any speed difference 
for local variables introduced via explicit assignment. Access to 
predeclared variables would use an optimized  access method, whereas 
access to variable names whose declaration point cannot be determined by 
statical program analysis would use a less efficient access method.

>If you have limited set of local variables, you can do something like:
>
>  require 'erb'
>
>  class Test
>    def initialize(path, *lv)
>      @erb = ERB.new(File.read(path), nil, '%')
>      @locals = {}
>      evalstr = "def run_erb\n" +
>        lv.collect{|k| "#{k} = @locals[\"#{k}\"]\n"}.join +
>        "#{@erb.src}\n_erbout\nend\n"
>      print evalstr, "\n\n"
>      eval evalstr, nil, path, 0
>    end
>    def values(hash)
>      @locals.update(hash)
>      hash.each {|k,v|
>        self.instance_variable_set("@#{k}", v)
>      }
>    end
>  end
>
>  t = Test.new("/tmp/test.rhtml", 'mumu')
>  t.values("mumu" => "HELLO")
>  print t.run_erb
>
>							matz.
>  
>
That's simlar to the way I "solved" "my problem" already. Thanks.

-- stefan