Paper folding machines are commonly used by all types of organizations. You might a paper folder in a corporate mail room, a government office, a school, a church or a print shop. All of these organizations process large numbers of documents and can greatly benefit from the assistance of a folding machine. However, each of these types of organizations has a special set of needs that need to be considered when choosing a paper folding machine. This article is designed to provide a list of five things that Churches need to consider when choosing a paper folding machine.

1. What types of folds do you need to produce? This is the first and most important question that you need to consider when choosing a paper folding machine. In general, most churches will need to fold their church bulletin and letters to congregation members. Generally, this means that they need to choose a paper folder that can do a z fold and half fold. However, some churches fold large format documents, legal sized church bulletins, tri-fold brochures or other materials. It is important that before you go shopping for a folding machine that you know what types of folds that you will need it to do.

2. How much folding are you going to need to do? This is an important question to ask when choosing a paper folder. More than likely the paper folder will be used to fold Church bulletins more than any other type of document. Ask yourself, “how many bulletins do we print each week?” If you are going to need to fold hundreds of bulletins every week you are going to want to make sure that you buy a paper folder that will hold up over time.

3. How often are you going to need to change folds? I know a lot of churches that very rarely ever change the settings on their folding machine. They use the folder for their weekly bulletins and nothing else. For these churches, a heavy duty paper folder with folding plates that are adjusted manually is ideal. However, other churches are constantly changing the settings on their folder to produce different types of documents (think to question one). If you plan on folding lots of different types of documents or are going to need to change the fold settings more than once a week it would be a really good idea to get a folder that has either easy to adjust fold plates or is completely digital.

4. What

Presenting for Presenters
<p style="padding-left:3em;"><em>If you are speaking at RubyConf this year, we have a special opportunity for you.</em></p> <h2>Are You Speaking at RubyConf 2008?</h2> <p>If so, congratuations! And have we got a deal for you &#8230;</p> <p>Wednesday evening, Nov 5, at 6:00 pm, (that&#8217;s the night before the conference) we are inviting all speakers to a special training session. I&#8217;m going to be sharing some ideas for putting together and delivering a good presentation.</p> <p>After my talk, Patrick Ewing and Adam Keys are geared up to do some Powerpoint Karaoke with everyone there. I&#8217;m not even sure what Powerpoint Karaoke is, but it sounds like fun.</p> <p>I hope to see everyone there.</p> <h2>Update (4/Nov/08)</h2> <p>I&#8217;ve talked to Adam today. He says that Patrick isn&#8217;t going to able to make RubyConf this year, but we will be ready to roll with Powerpoint Karaoke anyways.</p> <h2>Update (5/Nov/08)</h2> <p>It looks like the speakers training will be in the Olympic Room tonight. The Olympic Room is on the same floor as the registration desk. Go to the left past the elevators and turn right down that hall (or ask someone who looks like they know what they are doing).</p>
Articles are Back!
<p style="padding-left:3em;"><em>I&#8217;ve received a lot of requests for my old articles &#8230;</em></p> <h2>The Article Section has been Restored</h2> <p>When I changed to my new hosting machine, I moved all my blog posts but didn&#8217;t move any of the articles. Of course I <em>intended</em> to move them eventually but never got around to it.</p> <p>A lot of people have been asking for this article or that presentation, or pointing out that a number of old bookmarked links are no longer any good. So due to popular demand the <b>Articles and Presentations</b> section of onestepback.org is now restored.</p> <p>Enjoy</p>
Comments Are Now Enabled
<p style="padding-left:3em;"><em>I&#8217;ve gone without comments on this blog for a long time &#8230;</em></p> <h2>Comments via Disqus</h2> <p>I&#8217;ve gone through several commenting systems for this blog over time. First was the really cool <a href="http://onestepback.org/index.cgi/Tech/Web/MoreWebApps.rdoc">TagSurf</a> application that allowed commenting on about any web page on the internet arbitrary tags. Unfortunately, TagSurf died a (in the words of its creator) &#8220;well deserved&#8221; death.</p> <p>Then I tried a wiki for comments. That worked pretty good (aside from spam issues), but setting up a new page for comments for each new post was just too much hassle.</p> <p>Now I&#8217;m trying <a href="http://disqus.com/docs/about/">Disqus</a> for comments. It only took an hour or so to integrate Disqus with my ancient blogging engine (anyone else still using Rublog?).</p> <p>Kick the tires and see how it works. If you have feedback &#8230; well, just leave a comment.</p> <p>I guess this means I&#8217;ll have to start writing some <em>real</em> content here so there will be something worth commenting on &#8230; let&#8217;s see if there is anything I feel like ranting about &#8230;</p> <p>(Oh, and a hat tip to <a href="http://brionesandco.com/ryanbriones/">Ryan Briones</a> for pointing out Disqus when I was ready to go out and implement something from scratch.)</p>
RedMine For Rake
<p style="padding-left:3em;"><em>The is now a RedMine setup for Rake, FlexMock and Builder.</em></p> <h2>RedMine</h2> <p>As part of an effort to get better control of changes to the my open source projects, I&#8217;ve setup a RedMine issue tracking site for Rake, FlexMock and Builder. You can find it at <a href="http://onestepback.org/redmine">http://onestepback.org/redmine</a>.</p>
Moving Blog Host
<p style="padding-left:3em;"><em>I am changing host for the One Step Back blog.</em></p> <h2>It&#8217;s Time to Move</h2> <p>This is just a quick little post to let you know that the One Step Back blog is moving. In fact, it has already moved. But don&#8217;t worry, we aren&#8217;t going far.</p> <p>Originally this blog was hosted on a shared co-op system run by <a href="http://www.n2net.net/">N2Net</a>. It was dirt cheap and easy to maintain. The down side was that support was sporadic. As the hardware has aged, the Co-op has decided to let the current system run until the hardware dies, and then disolve the co-op.</p> <p>Today there are tons more hosting opportunities available than there were when the co-op was first formed. I&#8217;m now leasing a Linode <a href="http://www.linode.com/">node</a> and running the blog and other associated software from there. Its almost as inexpensive and the co-op and uptime <em>should</em> be better.</p> <p>Write now the blog has been moved. As time passes I&#8217;ll move the article archive as well. Let me know if anything looks amiss.</p> <p>&#8212;Jim Weirich</p>
How did you get started in software development.
<h2>Tagged</h2> <p>Looks like <a href="http://objo.com/2008/6/7/how-did-you-get-started-in-programming">Joe O&#8217;Brien</a> tagged me for answers to the following questions. He, in turn, was tagged by <a href="http://joshholmes.com/">Josh Owens</a>, who in turn was tagged by <a href="http://www.jeffblankenburg.com/index.html">Jeff Blankenburg</a>. It looks like <a href="http://www.codinggeekette.com">Sarah Dutkiewicz</a> and <a href="http://michaeleatonconsulting.com/blog/archive/2008/06/04/how-did-you-get-started-in-software-development.aspx">Micheal Eaton</a> started this.</p> <p>OK, sounds like fun. Here goes.</p> <h2>How old were you when you started programming?</h2> <p>I was introduced to programming in high school by reading a book on the topic. The book taught me how to write machine code for a strange decimal-based machine. Unfortunately, there was no actual computer involved in the process. Shoot, who had computers back then? Certainly not our high school (the personal computers? not invented yet!)</p> <p>In college, I learned a smattering of <span class="caps">FORTRAN</span>. Just enough to drive a Calcomp plotter to plot data from my undergraduate physics courses. But didn&#8217;t really get into programming until my junior year in college. (Story continued in next question)</p> <h2>How did you get started in programming?</h2> <p>So, I was planning out the courses for my junior year in college and I had a hole in my math courses. The math class I needed was not offered that semester, so my adviser suggested taking a computer programming course. He said it would be useful and, who knows, I might enjoy it.</p> <p>So I signed up for an introduction to <span class="caps">FORTRAN</span> course, figuring it would be easy because I already knew a little bit of <span class="caps">FORTRAN</span>. I show up on the first day of class and after a few preliminaries the instructor jumps right into some code, that looked like this:</p> <pre> (de member (pip deck) (cond ((null deck) nil) ((eq pip (car deck)) t) (t (member pip (cdr deck))))) </pre> <p>I remember scratching my head and thinking this was the strangest <span class="caps">FORTRAN I</span> had ever seen. I was totally confused for about three days, then something clicked on the third day of class. I suddenly &#8220;<em>got</em>&#8221; what the instructor was trying to get across and it all made perfect sense.</p> <p>If you haven&#8217;t figured it out yet, the instructor taught us Lisp as part of an introduction to <span class="caps">FORTRAN</span>. The instructor turned out to be Daniel Friedman, the author of <a href="http://www.amazon.com/Little-LISPer-Third-Daniel-Friedman/dp/0023397632"><em>The Little Lisper</em></a>, and was well known in the Lisp community. That small exposure to Lisp hooked me on programming from that point on. I took as many CompSci courses as I could in my remaining year and a half in college. I eventually graudated with a BS in Physics, but had a strong background in Computer Science as well.</p> <h2>What was your first language?</h2> <p>Technically, <span class="caps">FORTRAN</span> was my first language. But Lisp is the language I fell in love with and is what got me hooked on programming.</p> <h2>What was the first real program you wrote?</h2> <p>I have a very clear memory of the very first program I wrote professionally. The reason it is so clear is that this was the first program I wrote that was intended for actual use by someone who wanted it. Everything else up to that time was done for my own personal enjoyment or to satisfy some course requirement.</p> <p>The program calculated the &#8220;critical angles&#8221; of &#8220;pieces&#8221;. I was given the requirements by Anne Exline, a senior programmer, and proceeded to write the program to spec. It took a few days, but when I was done I showed the result to Anne and she was pleased with the result.</p> <p>The funny thing is that I had no idea what a &#8220;piece&#8221; was nor what was so critical about the angles I was calculating. I was so excited about writing an actual program that I did not ask until the software was done. When asked, Anne just looked at me funny and said &#8220;Rocket Pieces&#8221;. When Cape Canaveral lauches a rocket, they track it very carefully to make sure it stays on course. If it strays, the range safety officer is required to activate the self destruct. The critical angles are those angles that would cause the &#8220;rocket pieces&#8221; to land outside the safety area of the flight path.</p> <p>So, my very first professional program was not only useful, it might actually save lives.</p> <h2>What languages have you used since you started programming?</h2> <p>Languages I have used as part of my professional career (in roughly chronological order) include <span class="caps">FORTRAN</span>, various assembly languages, <span class="caps">FORTH</span>, C, PL/M, C++, Java, Ruby.</p> <p>Languages I have used in addition to those mentioned above: Pascal, Perl, Eiffel, and Lisp/Scheme.</p> <p>Languages I can read, but never wrote anything significant in them: Ada, Python, Erlang, Smalltalk, <span class="caps">SNOBOL</span>, Algol, Pascal.</p> <h2>What was your first professional programming gig?</h2> <p>I was hired by the <span class="caps">RCA</span> Missile Test project in Cape Canaveral, Florida as a Near Real Time Analyst. Duties included programming various launch related software (e.g. the critical angle program mentioned above) and working launch support.</p> <p>The launch support was the &#8220;Near Real Time&#8221; part of the job description. From the moment a rocket is launched until it reaches orbital velocity, any malfunction could cause it to fall back to earth. During this initial portion of the launch, the launch is monitored in &#8220;real-time&#8221; so that we know exactly where it would land if the engines were to cut off <span class="caps">NOW</span>. Trajectory calculations had to be done in fractions of a second and updated constantly in real time.</p> <p>After the rocket reaches oribital velocity (usually somewhere between 8 and 14 minutes into its flight), it won&#8217;t fall back to earth. At this point the real time trajectory program is shut down and the near real time program is started. The near real time program can take a few minutes to calculate a more exact orbital prediction and then send that prediction to downrange radars (e.g. the the <a href="http://en.wikipedia.org/wiki/Ascension_Island">Ascension Island</a> station) that won&#8217;t see the rocket until about 20 minutes after launch. It was the job of the Near Real Time analyst to run that program and provide oribital predictions for downrange station.</p> <h2>If there is one thing you learned along the way that you would tell new developers, what would it be?</h2> <p>Find something that you enjoy and do that. Life is too short to work in a job that you dislike.</p> <h2>What?s the most fun you?ve ever had ? programming?</h2> <p>Oh, the fun I have had. This story still makes me smile.</p> <p>My first computer was a single board <span class="caps">Z80</span> microcomputer with 4 KB of memory. I wrote a small <span class="caps">FORTH</span>-like interpreter for it and hacked a version of the animal game in <span class="caps">FORTH</span>. The animal game is a program that plays 20 questions to figure out what animal you are thinking of. It constructs a binary tree where each node is a question and the subtrees are the yes and no answers to the question. To play the game, all the program does is walk the tree, ask the question at the current node and follow either the <span class="caps">YES</span> branch or the NO branch as appropriate.</p> <p>If the program guesses wrong, it will ask you for your animal and a question that will distinguish your animal from the one it guessed. It then adds your question to the tree. By this extremely simple mechanism, it is able to expand its knowledge base. (see <a href="http://www.rubyquiz.com/quiz15.html">Ruby Quiz #15</a> for more details).</p> <p>I had just finished the program and had seeded it with a single animal, a mouse. I turned to my wife and asked her to play the game. She thinks of an animal and starts the program, which immediately asked her &#8220;Is it a mouse?&#8221;. She turned to me with surprise and said &#8220;How did it know?&#8221;. Of course, the animal she picked was a mouse.</p> <p>I don&#8217;t think I have ever impressed anyone with my programming skills as much as she was impressed with that game.</p> <h2>Who&#8217;s up next?</h2> <p>I&#8217;m tagging the following people. Remember, this is entirely voluntary so don&#8217;t feel obligated to answer. But I&#8217;m betting the answers are interesting:</p> <ul> <li><a href="http://mysterycoder.blogspot.com/">Chris Nelson</a></li> <li><a href="http://clarkware.com/cgi/blosxom">Mike Clark</a></li> <li><a href="http://gilesbowkett.blogspot.com/">Giles Bowkett</a></li> <li><a href="http://railsstudio.com/">Mark Windholtz</a></li> <li><a href="http://www.vanderburg.org/Blog">Glenn Vanderburg</a></li> </ul>
Rails Conf 2008 Summary
<h2>Conference Summary Video</h2> <p>Wow, what a great conference! There was a lot of energy flowing at RailsConf this year. Overall I&#8217;d rate this year as head and shoulders above last year. I&#8217;m not going cover much here, but will direct you attention to a <a href="http://www.railsenvy.com/2008/6/2/Railsconf-videos">Rails Envy VideoCase</a> that Greg Pollack put together. The video is a series of very short interviews with a number of presenters giving summaries of their own talks. The only downside with the video is that I wish it was available <em>before</em> the conference. I see there were a number of interesting talks that I missed.</p> <h2>Followup on the &#8220;Modelling Dialogue&#8221;</h2> <p>Joe O&#8217;Brien, Chris Nelson and myself did a dialogue style presentation on the difference between object modelling and data modelling. The most common question I got after the talk was requests for book titles to learn more about object oriented modelling. Here are the books that Joe, Chris and I have recommended:</p> <ul> <li><em><a href="http://www.amazon.com/Domain-Driven-Design-Tackling-Complexity-Software/dp/0321125215/ref=pd_bbs_sr_1?ie=UTF8&#38;s=books&#38;qid=1212463473&#38;sr=1-1">Domain Driven Design</a></em>&#8212;Eric Evans</li> <li><em><a href="http://www.amazon.com/Software-Development-Principles-Patterns-Practices/dp/0135974445/ref=sr_1_1?ie=UTF8&#38;s=books&#38;qid=1212502027&#38;sr=1-1">AgileSoftware Development, Principles, Patterns, and Practices</a></em>&#8212;Bob Martin</li> <li><em><a href="http://www.amazon.com/Refactoring-Improving-Existing-Addison-Wesley-Technology/dp/0201485672/ref=pd_bbs_sr_1?ie=UTF8&#38;s=books&#38;qid=1212465268&#38;sr=1-1">Refactoring: Improving the Design of Existing Code</a></em>&#8212;Martin Fowler</li> </ul>
Artichoke Music Rocks
<p style="float: right; padding: 0.5em;"><a href="http://www.artichokemusic.com/index2.htm"><img border="0" src="http://www.artichokemusic.com/LogocommUnity-sm.jpg"/></a></p> <p>The Musician&#8217;s Birds of a Feather gathering at RailsConf was great. We had a room full people, two guitars, a ukulele, a flute, several harmonicas and an improvised drum set. Unfortunately, one of the guitars was an electric travel guitar which had a dead battery, therefore no way to really hear it.</p> <p>However, the other guitar was a nice Epiphone accoustic which was passed from player to player. It became the quickly became the basis for most of the music performed that night.</p> <p>I want to thank <a href="http://www.artichokemusic.com/index2.htm">Artichoke Community Music</a> for supplying the guitar. Travelling with a guitar by plane is a big pain, so I arrived with nothing to bring to the music <span class="caps">BOF</span>. I called several local music stores looking for a guitar that I could rent for an evening. Artichoke music said they had a &#8220;not-for-profit&#8221; guitar that they would let me borrow for a day. Not many stores would do that for an out-of-town stranger.</p> <p>So, if you&#8217;re in Portland looking for a good guitar store, check out the great people at <a href="http://www.artichokemusic.com/index2.htm">Artichoke Community Music</a>.</p>
Test Driven Studio in June 2008
<p><em>Joe O&#8217;Brien and I will be leading another Test Driven Studio in Denver, June 9-11.</em></p> <p style="float: right; padding: 0.5em;"><a href="http://pragmaticstudio.com/images/studio/tdd-with-rails-icon.jpg"><img border="0" src="http://onestepback.org/images/pragstudio/studio-medium.gif"/></a></p> <h2>Testing, Colorado, June &#8230; What&#8217;s not to like?</h2> <p>About 8 years ago I come upon a technique that radically changed the way I developed code. I was reading Martin Fowler&#8217;s &#8220;Refactoring&#8221; book and came across this paragraph:</p> <p style="padding-left:3em;"><em>&#8220;Whenever I do refactoring, the first step is always the same. I need to build a solid set of tests for that section of code. The test are essential because even though I follow refactorings structured to avoid most of the opportunities for introducing bugs, I&#8217;m still human and still make mistakes. Thus I need solid tests.&#8221; </em>&#8212;Martin Fowler</p> <p>Chapter 4 of &#8220;Refactoring&#8221; was my first introduction to JUnit and got me interested in &#8220;Test First Design&#8221; (what we now tend to call &#8220;Test Driven Development&#8221;). Although I wrote <em>good</em> code before, the confidence I had in my code took a dramatic leap forward after I started adopting <span class="caps">TDD</span> practices.</p> <p>On June 9 through 11, <a href="http://objo.com">Joe O&#8217;Brien</a> and I will have the pleasure of leading the next Pragmatic Programmer&#8217;s <a href="http://pragmaticstudio.com/testing-rails">Test-Driven Development with Rails Studio.</a> in Denver. We will have an opportunity to share with you some of our experiences in using <span class="caps">TDD</span> with Ruby and Rails.</p> <p>There are still seats available, so its not too late to sign up. More information is available <a href="http://pragmaticstudio.com/testing-rails">here</a>.</p>
Lisp in Ruby
<p style="padding-left:3em;"><em>I stumbled across <a href="http://bc.tech.coop/blog/080101.html">this</a> and it got me thinking &#8230;</em></p> <h3>Update</h3> <p style="padding-left:3em;"><em>I&#8217;ve updated the Textile formatter on the site and the code for this entry is now displaying correctly. The previous version was swalling the == operators in the code.</em></p> <h2>Lisp 1.5 Programmer&#8217;s Manual</h2> <p>I stumbled across <a href="http://bc.tech.coop/blog/080101.html">this</a> in Bill Clementson&#8217;s blog and remembered using the Lisp 1.5 Prgrammers manual from the college years. I have strong memories of pouring over that particular page in the manual and attempting to understand all the nuances.</p> <p>If you&#8217;ve never read the Lisp 1.5 Programamers Manual, page 13 is the guts of a Lisp Interpreter, the &#8220;eval&#8221; and &#8220;apply&#8221; functions. It is written in Lisp, although the notation used is a bit funky. The entire interpreter (minus two utility functions) is presented on a single page of the book. Talk about a concise language definition!</p> <h2>In Ruby?</h2> <p>I had often thought about implementing a Lisp interpreter, but back in the &#8220;old days&#8221;, the thought of implementing garbage collection and the whole runtime thing was a bit daunting. This was in the day before C, so my implementation language would have been assembler &#8230; yech.</p> <p>But as I was reviewing the page, I realized that with today&#8217;s modern languages, I could problably just convert the funky M-Expressions used on page 13 directly into code. So &#8230; why not?</p> <h2>The Code</h2> <p>Here is the complete Ruby source code for the Lisp interpreter from page 13 of the Lisp Programmers manual:</p> <pre> # Kernel Extensions to support Lisp class Object def lisp_string to_s end end class NilClass def lisp_string "nil" end end class Array # Convert an Array into an S-expression (i.e. linked list). # Subarrays are converted as well. def sexp result = nil reverse.each do |item| item = item.sexp if item.respond_to?(:sexp) result = cons(item, result) end result end end # The Basic Lisp Cons cell data structures. Cons cells consist of a # head and a tail. class Cons attr_reader :head, :tail def initialize(head, tail) @head, @tail = head, tail end def ==(other) return false unless other.class == Cons return true if self.object_id == other.object_id return car(self) == car(other) &#38;&#38; cdr(self) == cdr(other) end # Convert the lisp expression to a string. def lisp_string e = self result = "(" while e if e.class != Cons result &lt;&lt; ". " &lt;&lt; e.lisp_string e = nil else result &lt;&lt; car(e).lisp_string e = cdr(e) result &lt;&lt; " " if e end end result &lt;&lt; ")" result end end # Lisp Primitive Functions. # It is an atom if it is not a cons cell. def atom?(a) a.class != Cons end # Get the head of a list. def car(e) e.head end # Get the tail of a list. def cdr(e) e.tail end # Construct a new list from a head and a tail. def cons(h,t) Cons.new(h,t) end # Here is the guts of the Lisp interpreter. Apply and eval work # together to interpret the S-expression. These definitions are taken # directly from page 13 of the Lisp 1.5 Programmer's Manual. def apply(fn, x, a) if atom?(fn) case fn when :car then caar(x) when :cdr then cdar(x) when :cons then cons(car(x), cadr(x)) when :atom then atom?(car(x)) when :eq then car(x) == cadr(x) else apply(eval(fn,a), x, a) end elsif car(fn) == :lambda eval(caddr(fn), pairlis(cadr(fn), x, a)) elsif car(fn) == :label apply(caddr(fn), x, cons(cons(cadr(fn), caddr(fn)), a)) end end def eval(e,a) if atom?(e) cdr(assoc(e,a)) elsif atom?(car(e)) if car(e) == :quote cadr(e) elsif car(e) == :cond evcon(cdr(e),a) else apply(car(e), evlis(cdr(e), a), a) end else apply(car(e), evlis(cdr(e), a), a) end end # And now some utility functions used by apply and eval. These are # also given in the Lisp 1.5 Programmer's Manual. def evcon(c,a) if eval(caar(c), a) eval(cadar(c), a) else evcon(cdr(c), a) end end def evlis(m, a) if m.nil? nil else cons(eval(car(m),a), evlis(cdr(m), a)) end end def assoc(a, e) if e.nil? fail "#{a.inspect} not bound" elsif a == caar(e) car(e) else assoc(a, cdr(e)) end end def pairlis(vars, vals, a) while vars &#38;&#38; vals a = cons(cons(car(vars), car(vals)), a) vars = cdr(vars) vals = cdr(vals) end a end # Handy lisp utility functions built on car and cdr. def caar(e) car(car(e)) end def cadr(e) car(cdr(e)) end def caddr(e) car(cdr(cdr(e))) end def cdar(e) cdr(car(e)) end def cadar(e) car(cdr(car(e))) end </pre> <h2>An Example</h2> <p>And to prove it, here&#8217;s an example program using Lisp. I didn&#8217;t bother to write a Lisp parser, so I need to express the lists in standard Ruby Array notation (which is converted to a linked list via the &#8220;sexp&#8221; method).</p> <p>Here&#8217;s the ruby program using the lisp interpreter. The Lisp system is very primitive. The only way to define the function needed is to put them in the environment structure, which is simply an association list of keys and values.</p> <pre> require 'lisp' # Create an environment where the reverse, rev_shift and null # functions are bound to an appropriate identifier. env = [ cons(:rev_shift, [:lambda, [:list, :result], [:cond, [[:null, :list], :result], [:t, [:rev_shift, [:cdr, :list], [:cons, [:car, :list], :result]]]]].sexp), cons(:reverse, [:lambda, [:list], [:rev_shift, :list, nil]].sexp), cons(:null, [:lambda, [:e], [:eq, :e, nil]].sexp), cons(:t, true), cons(nil, nil) ].sexp # Evaluate an S-Expression and print the result exp = [:reverse, [:quote, [:a, :b, :c, :d, :e]]].sexp puts "EVAL: #{exp.lisp_string}" puts " =&gt; #{eval(exp,env).lisp_string}" </pre> <p>The program will print:</p> <pre><code>$ ruby reverse.rb EVAL: (reverse (quote (a b c d e))) =&gt; (e d c b a)</code></pre> <p>All I need to do is write a Lisp parser and a <span class="caps">REPL</span>, and I&#8217;m in business!</p> <h2>The Example in Standard Lisp Notation</h2> <p>If you found the Ruby-ized Lisp code hard to read, here is the reverse funtions written in a more Lisp-like manner.</p> <pre> (defun reverse (list) (rev-shift list nil)) (defun rev-shift (list result) (cond ((null list) result) (t (rev-shift (cdr list) (cons (car list) result))) )) </pre>

types of papers are you going to need to fold? If you are going to need to fold heavy duty card stocks or glossy papers with your folding machine you are going to want to make sure that the folder can handle it. Many paper folders are not capable of handling heavy or coated paper stocks. In fact, even expensive folders often require card stock to be pre scored before being run. It is always a good idea to have your special papers tested in the paperfolder of your choice before you make your purchase. That way you will know for sure if they will work or not.

5. What sizes of papers are you going to need to fold? Again, it is important to try to anticipate the different types of documents that you are going to need to fold. If you think that you will need to make brochures out of 11” x 17” paper it is important to choose a folding machine that can handle this size of paper. Likewise, if the Church uses legal sized bulletins you will need a paper folder that can handle legal sized paper. Generally if you choose a folder that can handle 11” x 17” or larger paper then it will be able to handle all of the smaller sizes as well.

By asking yourself these five questions you should be able to focus your search for the right paper folding machine. Unfortunately, most churches end up settling on a paper folder that is not adequate for their needs and they usually regret it. Keep in mind that most paper folders that will stand up to the volume of folding that churches do will cost between $1200 - $3000 depending on the features that you require.