September, 2011 | Ryan Rampersad

scheme: more on nested procedures

A few days ago, I offered an primarily technical example on why Scheme’s nested procedure are actually pretty great. While it’s true the technical application applies, and probably more so in the more difficult exercises, I wanted to discuss the organizational methodology too.

Let’s say you write code like this. It’s code for tax bracket eerily similar to real life. For our purposes though, it looks like a complete and utter mess.

(define (tax amount)
	(define total
		(cond 
			((<= amount 35000) (* amount .15))
			((and (> amount 35000) (<= amount 100000)) (+ (* 35000 .15) (* (- amount 35000 ) .25 ) ) )
			((> amount 100000) (+ (* 35000 .15) (* 65000 .25 ) (* .35 (- amount 100000) ) ) )
		)
	)
	(if (> amount 50000) (+ total (* .05 (- amount 50000))) total )
)

This example goes like this: define the total as the result of the cond, where the cond will decide which bracket to use. Conceptually, it’s not really important to know how the tax is calculated to discuss organization. Plainly, this code is repetitive and obviously busy.

Using nested procedures though, we can clean it up. Since there are three brackets, let’s make three nested procedures. Granted, this may not look any simpler, but it is. That’s because the logic driving the calculations are abstracted away from the conditionals from which they originate. Indeed, this would definitely be better with some variables, but you can’t have everything.

(define (tax2 amount)
  (define (bracket1)
    (* amount .15)
  )
  (define (bracket2)
    (+ (* 35000 .15) (* (- amount 35000 ) .25 ) )
  )
  (define (bracket3)
    (+ (* 35000 .15) (* 65000 .25 ) (* .35 (- amount 100000) ) )
  )
  
  (define total
    (cond 
      ((<= amount 35000) (bracket1) )
      ((and (> amount 35000) (<= amount 100000)) (bracket2) )
      ((> amount 100000) (bracket3) )
    )
  )

 (if (> amount 50000) (+ total (* .05 (- amount 50000))) total ) 
)

Notice that last if-statement though? It still has some messy junk in there that’s still doing calculations. You could easily trim part of that down. But there’s a problem with trimming it down completely. Notice its use of total? It was previously defined as the value returned from the cond above it. If I were to refer to it in a previously defined procedure-within-a-procedure, possibly called state-bracket, I would get an error stating that total doesn’t exist yet, and that’s true, it doesn’t. What could I do? I could pass it in as an argument!

Notice the change in the last if-statement and the addition of a new nested procedure.

(define (tax3 amount)
  (define (bracket1)
    (* amount .15)
  )
  (define (bracket2)
    (+ (* 35000 .15) (* (- amount 35000 ) .25 ) )
  )
  (define (bracket3)
    (+ (* 35000 .15) (* 65000 .25 ) (* .35 (- amount 100000) ) )
  )
  (define (state-bracket)
    (+ total (* .05 (- amount 50000)))
  )
  
  (define total
    (cond 
      ((<= amount 35000) (bracket1) )
      ((and (> amount 35000) (<= amount 100000)) (bracket2) )
      ((> amount 100000) (bracket3) )
    )
  )

 (if (> amount 50000) (state-bracket total) total )

)

This code is abstracted more than it was originally. That means it’s more flexible and likely easier to read at a glance. I will admit that though that are improvements to be made. For instance, the concurrent repeating of constants could be eliminated. Personally, I feel setting a define up so that it has a conditional value is a hack, but apparently that’s the best way.

And that’s all about logical organization and abstraction with the nested procedures Scheme offers.

Happy abstracting!

scheme: factorial infinite recursion

My textbook explains basic recursion with the age old factorial. The problem with that is that the code given might be a tiny bit buggy if the expectations aren’t kept on the straight and narrow.

The given code from the book is:

(define (factorial n)
  (if (= n 1)
      1
      (* n (factorial (- n 1)))))

I left this code as is. Factorials are easy to understand, pick any n-value and multiply each value below it until you get to 1.

Imagine you made a call to (factorial 2). The result will be 2 because of 1 * 2. Then imagine (factorial 1), and the result being 1 because the truthy-branch of the if-statement is used instead of the calculation branch. So far, so good, right?

Now, imagine you had a call to (factorial 0). What happens? You’re going to get a dreaded infinite recursion error, which will look similar to this:

;Aborting!: maximum recursion depth exceeded

What could cause this behavior? Perhaps the author of this method simply really trusted himself to not miscount in his recursion. Perhaps it was an oversight, but whatever the case, look at the condition that controls the procedure. Notice if (= n 1), and that there is only a single value that will make this procedure stop, and that is 1.

To fix this to accept 0, while not affecting the result of the factorial numerically, you can simply exchange the (= n 1) with (< n 1). This will force a 1 whenever n is less than 1, so that covers 0 and all negative values.

Happy factorial!

Book Review: The Name of the Wind

In June I bought my first Audible audio book and it was The Name of the Wind by Patrick Rothfuss.

To save myself and you from having to read another long and inarticulate description, why not just read about it where justice is served chilled. Instead, I’ll tell you what I thought of it.

The best cover art for the book yet - mysterious and cold blue

I rate this book 4.5 stars out of 5, or on Amazon’s star rating, 4 out of 5. The book is repetitive in some parts and the initial setup is long and almost overwhelming, but after that, it gets better.

I suggest you pick up a copy and read it slowly. There are light spoilers below (e.g. what happens but not how it happens).

The book’s split time lines do nothing to confuse me. I know exactly when something is taking place – there is a definite distinction between the keeper-Kvothe and hipster-Kvothe in their style of talking and what is taking place. For instance, in the inn, nothing exciting happens except the two instances of mystical attacks from spider things and a possessed mercenary. Something like that, at any rate.

Kvothe reads his past out loud to his audience of both the scribe and his fairy helper Bast. It might seem odd at first to tell a story this way, but it essentially becomes its own book as if it were written in first person narrative form anyway. In fact, it might be better that the majority of the book is in the first person when listening in audio form. It feels as if Kvothe is telling you the story.

The most repetitive section is of Kvothe’s living the giant city, Tarbean. His poverty and depressing attitude was almost enough to make me lose interest in the long run. It feels as if it takes forever because there is no scientific magic in that part, but once it ends, the magic comes into the story pretty well.

You can imagine the book comprised of three parts, the first part of Tarbean, the second is comprised of his first struggles at the University where he gets kicked out of the library, meets his humanoid arch-nemesis and meets his girlfriend, and the third where Kvothe defeats a dragon of sorts. The ending is actually after the third part in his narration, but it feels as if the climax lies somewhere within heart of the dragon.

The struggles with Kvothe’s lover is interesting. She is mysterious and has men surrounding her most of the time, but she accepts none of them and she says it is because they are not understanding of her either. Kvothe tries to hide his feeling from her and she toys with him in a whimsical way, but neither admit their love for each other, although Kvothe is known to admire her in more than one way.

The magic introduced, sympathy as it is named, is unique from any other type of magic scheme I have encountered in my many years of reading fiction. It’s unlike the rhyming nature of Stile in the Apprentice Adept series and it is not elemental like that of the magic in Golden Sun’s Weyard. Of course in addition of the scientific magic sympathy, there is runic magic that rely on the same principles and alchemy but it is more than just slapping their hands together. The true mysterious magic is the magic of absolutely understanding so well, to know it’s name. Kvothe has a brief glimpse of the name of the wind late in the story and even while fleeting, it wields it powerfully.

The Name of the Wind is a long book full of exciting tales except for a few areas of prolonged engagement. It maintains a high standard of writing, excellent descriptions and well formed character interaction. In my case of the Audible audio book version, Nick Podehl voices Kvothe’s old and younger self differently making the transition points easier. His masterful interpretation of the forgien voices from Kvothe’s teenage friends from other countries also had depth to otherwise simple words on a page.

Fantasy is a hard genre. Harry Potter has ruined magic for children and many young adults and sparkling vampires have ruined the fairy creatures for the same audience. There is no book that will appease everyone, but this makes a great stab at penetrating the mind for the kids beyond their years.

scheme: nested procedures

Scheme unusually allows procedures within procedures. That nesting lets you easily reuse commonly repeated code and also adds organizational possibilities to your code base.

For instance, I once had to write a simple procedure for finding the maximum of four numbers. Without using the max procedure built into Scheme, that is.

This is just one way of doing it, but it’s a pretty clever way.

; maximum
; a,b,c,d - numeric arguments to determine which is the largest
; returns - largest numeric argument
(define (maximum a b c d)
  
  ; second procedure, within the first
  ; maxi
  ; x,y - numeric arguments to determine which is the largest
  ; returns - largest numeric argument
  (define maxi x y)
    (if (< x y) x y)
  )

; magic happens here, reusability!
(maxi a (maxi b (maxi c d)))

)

With this code, imagine the arguments were 1 2 3 4. The first maxi would decide which of 3 4 is larger. Then, it would hand it off to the next maxi up the chain, and it would decide which of 2 4 is larger, and so on until it gets to simply 4 as being the largest. Imagine you were then asked to increase the argument length to include 10 numbers, save the updating of the new argument names, all it takes is adding enough maxi calls to deal with 10 numbers (which would be 9 by the way).

Keep in mind though that this is not Scheme specific. This would work in Java the same way as well, but you would need two methods in a class to deal with it. Luckily, Java has the private keyword which makes it very similar to the way maxi is visible to the outside work: it is not.

Happy nesting!

scheme: can’t bind name in null syntactic environment

My Computer Science 1901 class uses MIT Scheme as its language of choice. While working in a lab yesterday, I ran across this error message.

Can’t bind name in null syntactic environment

My code looked similar to this example.

(define a 5) (define b 10)
(if (> a b) (define x a) (define x b) )

Notice the define statements in the if-statement? Well, that’s illegal. The problem is that the if-statement has its own temporary scope or environment in the professional schemer lingo.

To fix this problem, I switched my approach. Instead of defining the values inside the if, I could define the value with an if itself.

(define a 5) (define b 10)
(define x (if (> a b) a b) )

And this works just fine, x is set to the return value of the if expression’s evaluation. It’s that easy.

Happy scheming.

Tabs to Spaces in TextWrangler

I used TextWrangler for years in high school. It was better than Eclipse for quick and light needs when I was programming in Java. Earlier this year, I decided to stop using the tab key and replace them with spaces.

TextWrangler is setup by default to use tabs. Overriding is a little obscure. Go to TextWrangler > Preferences > Editor Defaults. Once there, tick the Auto-expand tabs checkbox and you can specify the number of spaces per tab-key in the Default font selector below.

Happy tabbing!

Remembering 9/11 – 10 Years Out

I felt that it was right to do a little public remembering. I never talked about 9/11 and how I was involved the last three years I have been posting, but the time is right, now, ten years out.

In 2001, was 8 years old and just starting third grade. Since it was a Tuesday, it was the second of week of school.

I woke up at 8am to get ready to catch the bus to get to school by 9am. I remember walking into my living room, my dad was sitting on the couch and my mom was behind him. He was watching CNN I think, and on the screen, there was a building that was smoking. I had never heard of The Twin Towers, the World Trade Center, before that. I knew planes could crash, though crashing into a ridiculously tall building is probably easier than it was to crash into a smaller one, it was unlikely.

The Second Plane coming in - What I remember as my key image

My cumulating vision of what happened that day - from 8 years old

I didn’t feel to too concerned. It didn’t feel like it was affecting me in the morning that day. I was just standing behind the couch watching the news about how a plane hit a building. As my parents explained though, I might have began to understand the purpose of the Trade Center.

The moment when I knew it didn’t just happen randomly was when I witnessed the second plane hit the other tower. The news was regularly discussing some pointless thing, as they always do even now, and the second plane comes into the view. There were about two seconds between entering the frame and colliding. At that moment, I knew. I knew it was on purpose. Nobody can not-miss a giant building twice. It’s impossible. It was a moment of realization that it was not an accident, it was not chance, it was clearly orchestrated. Even as an 8 year old, turning 9 in November, I knew these things to be true and I clearly remember thinking these things.

I went to school that morning. Nobody was really talking about it on the bus, or if they were, they weren’t talking to me. Maybe kids didn’t watch the news in those days. At school, in the class, with Mr. Young, I’m sure we heard about it though. I was early so I was watching with him, on the continuing coverage. Maybe it was there that I heard about the other planes.

Later that day, around lunch time and our normal recess, someone began talking over the PA-system. They explained what had happened to the towers briefly, but they also canceled our recess because it was unsafe. Unsafe? I know I thought this too, if a plane was going to hit a school, like those hitting the towers, it wouldn’t matter.

I remember feeling absolutely comfortable at school. When I was younger, I couldn’t figure out how it was possible. Why? 9/11 happened on Tuesday in what is likely the second week of school, so I would have already gone to school five days prior to the event. Was I able to be accustomed to my grade, teacher, room and new friends that fast? Apparently I was. I look back on that day and I don’t remember feeling out of place or feeling trepidation.

I don’t remember when the Towers fell. Maybe it was when I got back home at 4:15pm that day. Or at least, that’s when I saw it happen. I’m not sure. After that, I start to forgo certainty that I remember anything. In the following days, I’m sure I heard coverage on the events, on the Pentagon, the other crash and the entire attack. In fact, that’s probably when I heard it being called an attack.

In writing, this isn’t my very best description of my recollection of events. But it suffices, I think, to illuminate my place in 9/11. In my mind, I replay the scenes in better detail and clarity. I remember things that are not fitting towards a short narrative. These memories were of an 8 year old too, after all. Whatever I knew to be true then has changed by the colored perspective of who I am now.

Once I came up with this idea. When I think back on memories, I end up cauterizing them making them impotent. Maybe this happened with these memories too. Who knows?

Everyone says they have a memory of the biggest catastrophic event in their lives. So that, so far, is mine. But not really. As far as I am concerned, my life was relatively unchanged. Sure, I had to take my shoes off when I went to California four years later. Sure, I couldn’t wave my dad off at the Airport’s terminal when he had to attend his father’s funeral. So security changed. That’s not the impact I think everyone else claims they experience and feel.

Do I feel less free? Do I feel more proud?

Age has made me feel more free than ever before. I’m in college and I’m making course altering decisions every waking moment and I recognize them and their significance as well as I can when I make those choices. Do I feel more proud? Of the United States? Of our unwavering patriotism? Maybe. I like having flags. It’s the least I can do. There is no better place to live, but even with 9/11 as a catalyst for a paradigm shift, where history was before and after, it amounted to too little too late, perhaps, ten years out.

Have a great day, and a good week.

Note:

A lot of visitors are finding this page by searching for 9/11 images. The image I used above is doubtless under someone’s copyright protection. I absolutely admit I am using it without permission. If that is your image and you have verifiable rights on that image, I will remove it on request.

Useful Mail.app Shortcuts

I don’t mind Mail.app for most uses, it’s nice to have a native mail application. In Gmail, I use shortcuts. These are some of the shortcuts I’ve discovered in Mail.

Cmd+N – Starts a new message
Cmd+Control+N – Starts a new note (like a self-email)
Cmd+R – Replies to a highlighted message
Cmd+Shift+D – Sends a message
Cmd+Shift+N – Refreshes the inboxes
delete – Removes the message from the inbox (but leaves it in All Mail)

These shortcuts aren’t hard to find but unlike Windows, there are more functional keys on the Mac. This means there are more combinations and shortcuts than I would’ve expected. There are of course numerous other shortcuts but they’re a little hard to find in a single location.

The New Look

Four years ago, I unveiled my modern online presence with the purchase ifupdown.com. Three years ago this July, I created this blog that was formerly located at ryan.ifupdown.com. Last summer I bit the bullet and bought my own name as a domain, ryanrampersad.com. Earlier this year, in early May, I brought my blog out of the dark ages with a new and bright theme. Today, I’m pushing out a new front page that will represent my entrence into college and beyond on ryanrampersad.com.

The old front page did little to promote finding me online. As that page is directly visible on my business cards, in my email address and essentially is the #1 in Google Juice™ for “ryan rampersad”, it is important to utilize the landing and funnel people into other avenues of connecting with me.

The new design has some technical bonuses. It is based off of HTML5 with the NormalizeCSS. It’s so much easier to use than the ResetCSS of the days of yore. In fact, I wrote my own grids because after all the time I’ve spent trying to get frameworks to stop sucking, I realized it’s actually easier to calculate the sizes, paddings and everything myself. And the flexibility is infinite too, so it’s better this way.

The design high lights two aspects better: me and social. Me as in my huge name sprawled across the top and social as in my nice array of badges representing my socialite locations.

It’s not a big leap, but it was enough to look refreshed.

That is all.

Disqus Spam

I love Disqus for what it tries to offer: a seemless commenting system that links all the comments across the land into a nicely bundled profile. It makes liking good comments easy and it also saves people the trouble of having multiple logins for what amounts to about twenty words.

That said, Disqus has a problem. It gets spammed. When there is spam on Disqus, it’s usually obvious. I said twenty words because comments left by humans are usually short unless they’re arguing a point or ranting. And humans don’t tend to sell $32 iPads on an article about Android phones. I read a lot of blogs and this is the only kid of spam I see on Disqus. I see it at least twice a day on high profile blogs. That may not be much, but it’s there and it’s getting through.

Disqus Spam - No, this has nothing to do with me, stop digitizing the contents of this image into your database of keywords

Having never used the Disqus system before, I am not familiar with the moderation settings. Does the comment host need to approve each message? Is there a ranking so that if a person gets enough likes or previously approved comments, they are trusted? Is there no Akismet like scanning of comments before hand? Without Akismet, this blog would get at least 500 spammy comments per day.

So, what’s going on back there, Disqus, that allows spam through that is so obvious?

Motorola Triumph At Target

The Motorola Triumph has had deals at Best Buy for a long time now, but with a catch. Target has actually had the Triumph for a couple of weeks at a local store but hasn’t put it in a promotion until this week. I can only hope more deals like this emerge a little later too, since I’m not ready right now.

On page 14 of this week’s Target ad, 9/4 to 9/11, the Triumph is offered at $299.99 with a $50 Target gift card.

It’s not as good as other deals Target has run, but it’s decent. From the ad, it appears there is no initial activation catch like that of BestBuy. So that’s something at least. You could buy a phone and, get cake and ice cream to celebrate.

Expect more, pay less.

A Tiny Epiphany – Apple’s Point

In the basement of Coffman Union on Wednesday while waiting for Welcome Week activities to start, I was idly listening to an Audible audio book. I realized that I hadn’t thought to check my bus schedule for the ride back home later that day.

I had choices: find a computer, use my computer, use the browser on my phone or just ask someone. Going in order, finding a computer is easy since there’s a lab in Coffman but I didn’t need to check in just for that. Using my laptop wasn’t an option because I didn’t bring it to Welcome Week. I figured I’d be, you know, busy. Asking someone? No way.

Using the browser on my phone was the solution. My epiphany came from this moment. I attempted to look up my bus schedule. Here’s how it went down.

Make two swipes to slide the unlock bar on the lockscreen; the first one didn’t register right.
On the Audible control screen (where the scrobbler, pause, play, fast forward and so on are), hit home key
On the homescreen, hit the tiny browser icon in the lower right corner
Wait for it to launch
Tap into the address bar, wait for the keyboard to come back up
Very slowly and deliberately type metrotransit.org, make a few mistakes, retype and so on
Wait patiently for the slow Wifi-G speeds to deliver my page
Tap the Trip Planner, target the text fields, type the proper addresses
Attempt to scroll down the page
Read the schedule information
Sigh, because it took forever to do all this

Really, it’s not so many steps. But that’s when you don’t feel the bad stutters for transitions, the slow keyboard input and annoying short interface freezes. These things add up.

I wanted to write about this on Wednesday. I realized why people like these Apple products so much. In the basement at Coffman, I realized I wanted to reach for my MacBook Air and write. Just write. I wanted to reach for my phone and just look up that transit schedule, get it done and get back to listening to my audio book.

Android works well. I love using it and it’s just fine. But you know that moment when you’re doing something you enjoy and the next moment you need to actually get something done? I had that moment and I felt like my phone was getting in the way. So it’s a small epiphany. The way I would use the iPhone is probably the way Microsoft intends with their system, get in, get out, and get back to life (or a completely fictional futuristic science fiction audio book). The phone shouldn’t, at the very least, get in the way of doing something on the phone. Android is simple; there isn’t an endless amount of configuration, there is no secret about:config in Android that allows me to tweak everything. I don’t need that either. I just need the speed to get things done.

Get back to life.

Too Many Email Accounts

At the University of Minnesota, I’m lucky enough to get a Google Apps powered email account. Of course, I retain my personal accounts, the childish daybreak and the slightly better ryan.rampersad. And this discounts my other aliases and my domain’s Google Apps. It should suffice to say that there are way too many email accounts.

The details are pretty scary. My main personal account right now is daybreak due to a lack of planning and foresight, but I live with it. It collects my mail from my business, pro-personal (e.g. hipster), a couple aliases and now my UMN address. So I have all this email going back into one inbox. You’d think it would get full but I don’t get that much email from those accounts yet, but the usage rate has dramatically increased as my access has, starting from my iPod touch last fall and Android phone this winter.

But then there’s the other end. When I get an email, say my hipster account from my boss, it goes to my daybreak inbox. I would be shamed to send it out from that address so I have to enable Send on Behalf… and superficially link all these accounts back to daybreak.

It’s a two way street in this respect. I collect the mail into one account and I send out from one account. It sucks that these cannot be separate because there is no universally accessible cross platform email client that doesn’t suck.

Google hasn’t addressed this multiple account syndrome yet. I’m looking forward to a Sparrow for the web. It’s a breathtakingly simple way to fix email; short, concise and thoughtful with a familiar interface akin to just about any Twitter client. This sound a lot like that identity problem everyone’s talking about these days.

Gmail changed email and now I want something to do it again.

✉