From: Jim Weirich <jweirich@...>
Date: 2003-03-15T19:39:25+09:00
Subject: Re: The onion truck strikes again ... Announcing rake

On Sat, 2003-03-15 at 04:09, Seth Kurtzberg wrote:
> > I see this functionality as an add-in library.  I already have a stand
> > alone program (called jdepend.rb) which determines the dependencies in a
> > Java project.  I can see reworking the jdepend code so that it can be
> > used as a library and then in your Rakefile have ...
> >
> >     require 'jdepend'
> >     JDepend.generate_java_dependencies
> >
> > or something like that.  Since a Rakefile is really Ruby code, its
> > trivial to extend it in ways that are difficult in a Makefile.
> 
> True, but there are also disadvantages to that approach.  Specifically, either 
> you are using code in the makefile to generate itself (as in appending 
> additional dependency rules), or you use a second file to hold additional 
> dependencies.  Both are undesirable.

I've done both with Makefiles, but that's not what I am suggesting. 
Consider the following code (which could be placed directly in a
Rakefile)...

    Dir['src/**/*.java'].each do |srcfile|
      classfile = srcfile.sub(/^src/, 'classes').sub(/\.java$/, 'class')
      file srcfile
      file classfile => [srcfile] + dependencies_for(classfile) do |t|
        sys %{javac -classpath classes -sourcepath src #{t.name}}
      end
    end

That code directly recreates the dependencies without generating the
text of the Rakefile.  It would be run afresh every time a Rakefile is
loaded.  Of course, calculating dependencies could be a time consuming
operations, so perhaps you wouldn't want to do it this way ... but you
could (very easily).

I think there are some very interesting possibilities here.

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)