From: "Dan Stevens (IAmAI)" <dan.stevens.iamai@...>
Date: 2008-09-03T22:43:35+09:00
Subject: Re: [QUIZ] Where the Required Things Are (#175)

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I've had a go at a solution, but I don't think what I did works properly.
Feel free to comment on what's wrong with it.


RUBYGEMS = 'rubygems.rb'

# Create a copy of the load path ($:)
@load_path = Array.new($:)

# Replace '.' in @load_path with full directory path
@load_path[@load_path.index('.')] = Dir.pwd

# Enforcing the require of rubygems before aliasing Kernel#require makes
things
# less troublesome.
begin
    # If rubygems has been loaded, append the its path(s)
    @load_path.concat(Gem.path) if require RUBYGEMS
rescue LoadError
    # A LoadError will occur if rubygems isn't installed, but it should be
safe
    # to ignore.
end

module Kernel
    alias :old_require :require

    # Make our own require method that uses '@load_path' variable to find
the path
    # of the file given by 'string'
    def require(string)
        old_require string

        # If 'string' doesn't have an extension
        if File.extname(string).empty?
            exts = ['.rb', '.so', '.o', '.dll']
            until exts.empty?
                fname = string + exts.shift
                path = @load_path.find { |i| File.exists? File.join(i,
fname) }
                return File.join(path, fname) unless path.nil?
            end
        else
            return @load_path.find { |i| File.exists? File.join(i, string) }
        end
        raise "If you can read this, Kernel#require was able to find a
library " +
                "named #{string} but #{__FILE__} was not able to. Either
there is" +
                "bug in #{__FILE__} and/or Kernel#require's search method is
" +
                "different to #{__FILE__}'s"
    end
end

if $0 == __FILE__
    ARGV.each { |a| puts require(a) }
end


2008/8/29 Matthew Moss <matthew.moss@gmail.com>

> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>
> The three rules of Ruby Quiz 2:
>
> 1.  Please do not post any solutions or spoiler discussion for this
> quiz until 48 hours have passed from the time on this message.
>
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> permanent, new website is in the works for Ruby Quiz 2. Until then,
> please visit the temporary website at
>
>     <http://splatbang.com/rubyquiz/>.
>
> 3.  Enjoy!
>
> Suggestion:  A [QUIZ] in the subject of emails about the problem
> helps everyone on Ruby Talk follow the discussion.  Please reply to
> the original quiz message, if you can.
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>
> ## Where the Required Things Are (#175)
>
> Occasionally, I've taken a look at the source for some Ruby module,
> often because there is no manual or man page, or what documentation is
> available is outdated or incomplete. Or sometimes I just want to see
> how some Ruby stuff is implemented.
>
> One such example was from the previous quiz: I want to learn more
> about the Sys::Uptime module. I have it installed, and the call to
> `require 'sys/uptime'` works, but I don't know how to use it. But,
> alas, I also don't know where the installed files are located. The
> shell command `which` doesn't help here, since the module is unlikely
> to be in the shell's executable path.
>
> What I would like is a script that works like `which` but for Ruby
> modules. Examples:
>
>    > ruby modwhich.rb "sys/uptime"
>    require 'sys/uptime' =>
> /opt/local/lib/ruby/vendor_ruby/1.8/i686-darwin8.11.1/sys/uptime.bundle
>
>    > ruby modwhich.rb date
>    require 'date' => /opt/local/lib/ruby/1.8/date.rb
>
> For extra credit, preserve this behavior when modwhich.rb is the main
> program, but slightly different behavior is modwhich.rb is required by
> another script:
>
>    > ruby -r modwhich upsince.rb
>
>    require 'sys/uptime' =>
> /opt/local/lib/ruby/vendor_ruby/1.8/i686-darwin8.11.1/sys/uptime.bundle
>    require 'date' => /opt/local/lib/ruby/1.8/date.rb
>    Last reboot: 2008 Aug 22 at 18:49
>
> Note that we allow upsince.rb to run as normal; the output of
> modwhich.rb is mixed into stdout.
>
>
> --
> Matthew Moss <matthew.moss@gmail.com>
>
>

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