Lauren Ipsum: A Story About Computer Science and Other Improbable Things Read online

  That’s when she came to the first fork in the path. Each fork had its own sign. The left-hand sign said

  THINGS

  and the right-hand sign said

  IDEAS

  Laurie had seen a lot of Ideas lately. A simple Thing would be a nice change. She took the left-hand path. A minute later she came to the next fork. The signs there said

  FAMILIAR THINGS | STRANGE THINGS

  “I’ve seen a lot of Strange Things lately, too,” she said. “I’ll go for Familiar.”

  YOUNG | OLD

  “Um . . . Old!” Down the right-hand path they went.

  INTERESTING | BORING

  “That’s an easy one,” said Xor. “Interesting.”

  “You’re not the one who has to climb rocks and cross scary bridges when we make Interesting deliveries,” Laurie said. “But okay.”

  LOST | UNLOST

  “How can you have a sign pointing to Lost things? Wouldn’t that make them Unlost?” asked Xor.

  “Maybe they’re only Lost until you find them,” Laurie mused.

  “That makes sense.” Xor replied. They took the left path.

  MOSTLY LOST | COMPLETELY LOST

  “Comp . . . no, Mostly Lost,” Laurie decided. Left again.

  “You know, I don’t see millions of paths,” said Xor. “There’s only ever two.”

  SMALL | NOT-SMALL

  “Not-Small!” they said together.

  BIGGER THAN YOU?

  NO | YES

  “Everything is bigger than me,” said Xor. “Let’s go right.”

  BIGGER THAN A MOUNTAIN?

  YES | NO

  Not that big! They went right again.

  TALLER THAN A LIGHTHOUSE?

  NO | YES

  Laurie had seen quite enough of lighthouses, too. She tried to go left, but a Shelled Green Round animal barred the way.

  “We meet again, Miss Ipsum,” it said.

  “Mister Tortoise! What are you doing here?”

  “I’m enjoying a special treat,” said Tortoise, taking a bite out of the greenery. “I help keep the mandelbroccoli bushes in the Garden nice and trim. For me it is a delicious chore. And what are you doing here, Miss Ipsum?”

  “I’m looking for the nearest exit so I can deliver a letter.”

  Tortoise seemed to smile. Of course, he always seemed to be smiling. “There are millions of paths through the Garden. All of them are exactly the same length.”

  She tried to picture so many paths side-by-side. “I don’t understand. If there are so many, where are they?”

  “They are all around you. Every path forks off from another path,” Tortoise said. “One path becomes 2, 2 becomes 4, then 8, 16, and so on. After 24 forkings, there are over 16 million different paths.”

  “Oh! It’s the Power of Two again. But this time it gets bigger instead of smaller,” Laurie said.

  “Exactly right. You are currently on the path to Things that are Familiar, Old, Interesting, Mostly Lost, Bigger Than You, and Smaller Than a Mountain,” said Tortoise. “I suppose I am one of them.”

  “So how do I choose which forks to take?”

  “I suggest choosing wisely. Good day, Miss Ipsum.” Tortoise turned and walked slowly and steadily down the left-hand path.

  “Wait! I don’t know what you mean!” Laurie ran after him. Catching up with a Tortoise should have been easy. But with every step he got farther and farther away. By the time Laurie got to the next fork, he was nowhere to be seen.

  FRIENDLY | UNFRIENDLY

  “What do you think, Xor? Which way?”

  “Do you really want to see a Garden full of Unfriendly Things?”

  “Good point.” She went left.

  IN THE AIR | ON THE GROUND

  They didn’t want to see anything bigger than them that also could fly, no matter how Friendly. Anyway, Tortoise was on the ground.

  LIGHT | HEAVY

  “Heavy for sure!” shouted Xor.

  LIVES OUTSIDE | LIVES INSIDE

  “Tortoises live outside, don’t they?” Now that she thought about it, Laurie wasn’t completely sure. But it seemed like a good guess!

  NEVER SLEEPS | SOMETIMES SLEEPS

  “And they definitely sleep,” said Xor. Right they went.

  SLEEPS AT NIGHT | SLEEPS DURING THE DAY

  “Sleeps at Night!” Laurie shouted. “We should be getting close!”

  MANY COLORS | ONE COLOR

  Laurie ran down the left-hand path without stopping to think. But wasn’t Tortoise only one color? It was too late to go back.

  QUIET | NOISY

  “I don’t like Noisy Things,” she said. “Tortoise is pretty quiet.”

  PLURAL | SINGULAR

  “What does that mean?” “Plural means more than one. Singular means only one,” Xor said. They went right.

  NATIVE | FOREIGN

  “I know this one,” said Laurie. “Native means from here. Foreign means from somewhere else. Native!”

  EXPECTED | UNEXPECTED

  “I wonder where we’ll end up,” she said as they turned right. “What is Familiar, Old, Interesting, Mostly Lost, Bigger Than Me but Smaller Than a Mountain and Shorter Than a Lighthouse, Friendly, On the Ground, Heavy, Lives Outside, Sleeps at Night—” (she paused to breathe) “—has Many Colors and is Quiet, Singular, Native, and Unexpected?”

  YOUR WISH | SOMEONE ELSE’S WISH

  “MY wish!” said Xor and Laurie at the same time. They giggled and walked down the left path. The next sign made them think for a moment. It asked

  ARE YOU SURE?

  YES | NO

  “Sure, I’m sure!” said Laurie. “Why would I ever want someone else’s wish?” She went down the left-hand path. “I think we’re almost through the Garden, Xor!”

  She started walking fast, then jogging, then running again down the long green hallway. Xor was getting excited too, turning all sorts of polka-dot colors. Laurie was already thinking about what messages she wanted to send to Fresnel, and Tinker, and—

  “Oh no!”

  Laurie stopped dead in her tracks. In front of them was another forking. The last one.

  The left-hand sign said

  HAMILTON (LAURIE’S WISH)

  And the right-hand sign said

  AUNT VANA (XOR’S WISH)

  “The Garden guessed my wish!” Laurie said.

  “Mine, too,” Xor said.

  Laurie started to go left, then stopped. Then she started to go right, but had second thoughts. They stood there for a very long and very silent minute.

  “We can only take one path,” said the girl.

  “Yeah,” the lizard replied.

  “And there’s no going back.”

  “That’s the rule.”

  “You really want to find your aunt,” Laurie said.

  “And you really want to go back home,” Xor sighed.

  “That means we have to choose,” Laurie said. “But how?” She did want to go home, but she also wanted Xor to find Aunt Vana. She wanted to bring Xor and Vana home with her and how cool would that be and—

  “No, Laurie,” Xor said sadly. “It means we have to split up.”

  “But—”

  “Only One Visitor Per Path. That’s the rule.” He jumped off her shoulder and landed on the right-hand sign. “I guess . . . this is how you found me.” His skin turned orange and purple.

  “We can do this,” said Laurie, thinking furiously. “Once you find your Aunt Vana, take her to the Treelighthouse. I’ll find a way to come back. Or maybe I’ll get a telescope and a big light and—”

  “We’ll see each other again,” Xor said.

  “Okay,” said Laurie. “Promise?”

  “Promise.”

  “And I’m going to whistle, okay?”

  “Okay.”

  “So you can hear me.”

  “Right,” said Xor.

  “It’ll be fine.”

  “Absolutely,” agreed Xor.

  “Here I go.”
r />   “Me too.”

  Laurie did try to whistle, but it’s impossible to whistle and cry at the same time. Just try it.

  Chapter 20. Fin

  The mandelbroccoli bushes got shorter and wilder until they blended in with the forest. Laurie didn’t know where she was or where she was going. But she knew how to get there. At least, she hoped she did. By now it was late afternoon and the shadows were getting longer.

  The trees of the forest were large oaks and maple, with an occasional pine or spruce. There were a number of saplings and bushes of various sorts. It was hard to see far because of all the leaves, but walking was easy enough if she skirted the spruce and berry bushes.

  “Chirrrup!”

  Laurie’s heart started pounding. More Jargon? How many? Where?

  “Chirrrup!”

  No running this time. She walked toward the noise as quietly as she could. It seemed to be behind a large tree. No, not a Jargon. It was . . . a squirrel. An ordinary squirrel. It yelled what were probably very nasty things in Squirrel, then ran up the tree to safety. And that tree! She recognized it. It was the big tree behind her house, at the edge of the woods . . .

  Laurie was home.

  * * *

  Lying in her own bed after a hot bath made Laurie feel happy and tired. As far as her mother knew, Laurie had been gone only an hour or two. To Laurie, though, it felt like at least a week since she’d gotten lost in the woods. She was too sleepy to think about it. She hoped Xor had gotten his wish and was learning how to blend in. She was sad that she didn’t get to see her new friends again. She had promised to come back . . . after delivering . . . delivering that letter . . .

  Two seconds later, she was out of bed and tearing open the plain white envelope.

  Hi, kiddo. If you’re reading this letter, you’ve figured out who it was for. I wasn’t sure the Garden would actually work, and I don’t like good-byes.

  You helped us build the Network. We couldn’t have done it without you. Fresnel says once you learn a few things and unlearn some others, you’ll make a good Composer.

  See you around,

  capt. Winsome “Losesome” Trapp

  She read it twice before she noticed that Winsome’s last name was Trapp. It made sense. For all of the sour things Winsome had said about Colonel Trapp, they were a lot alike, sending strange messages and bossing people around. It looked like Laurie wasn’t the only one who had trouble getting along with her parents.

  She lay down again and thought about tomorrow. Tomorrow was the first day of summer school. It didn’t sound as scary as it did before. If she could navigate the Byzantine Process, beat Ponens and Tollens, make infinite strings, and teach turtles to build towers, sitting in a classroom didn’t sound that hard at all.

  She might even learn something interesting.

  The End

  Chapter 21. One More Thing

  It was a dark and foggy night, many months after Lauren Ipsum had gone back home to Hamilton. A lighthouse flashed. Flashed. Flashed. Flashed.

  The flashes didn’t carry any messages this night. The fog was too thick to send signals, so the Network was down. The powerful lights were needed for their original purpose: to warn boats away from dangerous rocks.

  As it happened, only one boat was around, and it didn’t need warning. It was exactly where it was supposed to be.

  The Jargonaut was the boat, and Kevin Kelvin was its captain. The boat was large and flat and plain. Near the front was a little cabin where Kelvin lived. The rest of the deck was taken up by a crane and a winch—a machine built to wind wire in or out. A wire led from the crane and into the water, looking like a large fishing pole. Belowdecks was mostly a hold for tons and tons of coiled wire.

  It wouldn’t be accurate to say that the Jargonaut was a gigantic boat with a winch attached to it. That might give you the wrong impression. It would be better to describe it as a gigantic winch with a boat attached to it. Its entire purpose in life was to play out and wind up miles of heavy wire.

  Inside the cabin, Kevin Kelvin rubbed his hands together to keep them warm. A thermometer hung from a peg near the door. It read a chilly 273. Brrrrr! Now, 273 degrees might sound pretty hot to you and me, but this thermometer didn’t measure in degrees Fahrenheit or Celsius. It was on the Kelvin Scale, one of the captain’s many inventions. The Kelvin Scale starts at Absolute Zero, the coldest that any cold thing can possibly get. And 273 Kelvin isn’t much better. It’s about the temperature of an ice cube. Brrrrr!

  The thermometer said a lot about the kind of person Kevin Kelvin was. He was a Composer, and a wickedly smart one. He never let a good idea escape without putting his name on it.

  When people asked Kelvin what he was doing, he would say he was fishing. He never explained what he was fishing for, in the middle of the night with a gigantic winch that had a boat attached to it. When people made jokes about catching sea monsters, Kelvin only smiled. No one knew what he knew. How could they?

  Kevin Kelvin was fishing for teeny-tiny bits of electricity flowing up his Wire. The Wire traveled under the ocean for miles, all the way to a little building on the shore, not far from the lighthouse. He twiddled dials, and listened carefully to a nearby speaker connected to the Wire, and made notes. If his ideas were right, any moment now he should hear a signal from his assistant on the other end. It would sound like—

  BEEP.

  His skin tingled with excitement, but he didn’t dare make a sound.

  BLOOP. BEEP.

  Kelvin quickly disconnected some wires and connected some other ones. He flicked a switch on and off.

  FLIP. FLOP. FLIP.

  The Wire answered back.

  BLOOP.

  The Wire worked! Just as Kelvin thought: he could send messages using electricity, even under miles of seawater. If the Jargonaut laid down a Wire all the way between two islands, that would form the first link in Kelvin’s very own Network. A Network that could send messages all the time, even on a terrible night like this. A Network that, someday, could even have multiple Wires.

  Those fools up there in their ivory towers, flashing their little lights, will never know what hit them!

  The Field Guide to Userland

  You might have wondered whether this or that part of the story is real. Can you really make a Fair Coin out of an Unfair Coin? Can you really use ants to find shorter paths? Yes, you can do both—and a lot more besides. In this guide, you’ll find out how some of the places, people, and things Laurie encounters in Userland connect with our own world.

  Chapter 0: Mostly Lost

  Jargon

  In the real world, jargon doesn’t look like a mouse-dog, or even a dog-mouse; it looks just like an ordinary word! Computer scientists (and really, all scientists) love inventing new words. We call these specialized words jargon or argot. Jargon can be good, because it saves time when you’re discussing things with your colleagues. It can also be bad, because it excludes nonexperts from the conversation.

  When you’re just starting out with programming, all the jargon, argot, and weird new words can be intimidating, but don’t let that stop you from learning. Jargon can be silly, or powerful, or dangerous, depending on how you use it. But no matter what words you use, if you always obfuscate instead of explicate, no one will understand you!

  Wandering salesman

  The Traveling Salesman problem is a classic computer science question. Given a group of cities, your goal is to find the shortest Hamiltonian path, a route that lets you visit each city only once. If you have a large number of cities, it would take a very long time to calculate that path, even for a computer. So the Wandering Salesman might be on the road for quite a while!

  Instead of calculating the exact answer, the salesman looks for a path through all the towns that’s close enough to being the shortest. A very interesting aspect of the Traveling Salesman problem is that humans are pretty good at solving small examples by hand. There is much discussion about what algorithm people use in their
heads while solving it. See also Hugh Rustic (Chapter 8; Chapter 8: More Than One Way to Do It).

  The Upper and Lower Bounds

  In Userland, the Upper Bounds are a mountain range, as tall as anything can be. The Lower Bounds are valleys as low and deep as anything can be. Nothing can be higher and nothing can be lower than these two bounds.

  In the real world, finding an upper and lower limit on a problem can simplify things a lot. Say you have to guess a person’s age. It’s unlikely that anyone is over 150 years old, and no one can be younger than 0 years old. So, 150 is the upper limit and 0 is the lower limit. You can narrow down the bounds even more with simple questions. Is the person still in school? If so, then he is probably younger than 30. Can the person drive a car? If so, then he is probably older than 15.

  Mile Zero

  You sometimes see signs that mark a point on a highway, like “Mile 14.” Now, if there is a Mile 14, then there must be a Mile 13, and a Mile 12, and so on. Everything has to start somewhere, and Zero is where it starts. Possibly the most famous Mile Zero is in Key West, Florida. It’s at the beginning of US Route 1, which goes all the way to Canada. If you look carefully and are very lucky, you might find a Mile Zero near where you live.