If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

The naive method to solve this problem is to go through all the numbers from 1 to 1000, and add it to a running sum if it’s divisible by 3 or 5. Here’s how to say that in python:

sum = 0
for x in range(1,1000):
  if x % 3 == 0 or x % 5 == 0:
    sum += x

Since we’re in the age of the computer, we don’t have to worry about speed issues, but let’s assume we do, when running this code substituting one million for one thousand, it takes a few seconds to reach the answer of 233333166668. There should be a faster way.

Let’s assume that you can figure out a way of telling what the sum of multiples of a certain number below a given number is. Then answering this problem would be as simple as writing

sumofmultiples(3) + sumofmultiples(5) – sumofmultiples(15)

Luckily we have such a method Lets say you have to add all the multiples of 3 from 1 to 100, you would end up adding 3+6+9+12+15+18+…+99 this is the same as adding up 3*(1+2+3+4+5+…+33). If you’ve taken a math course you know that 1+2+3+…+x is equal to x*(x+1)/2 . This allows us to rewrite our code as:

def sumofmultiples(x, max):
  n = (max -1) /x
  return n*(n+1)*x /2
sumofmultiples(3,1000) + sumofmultiples(5,1000) - sumofmultiples(15,1000)

Which runs at a pretty speed for many values of x.

Instead of simply using droopy for transferring files, I’ve taken this as an opportunity to learn more, and I’m slowly modifing droopy to act as a general purpose web server. At the moment it serves up a webpage with a random picture, that refreshes with Ajax at the click of a link. Not impressive, but not bad for the first time I’ve touched either python or javascipt.

My future plans are to first make the system more easily extensible, by pulling out scripts and css styles into their own files. Afterwards I’m going to make a simple picture sharing/rating site. You upload your picture with an optional caption, and others thumbs up or thumbs down your picture.

You can find the current version of the server running at brian.chickenkiller.com and you can get the modified droopy source here.

There should be some kind of app that when you go to your inbox instead of seeing the old messaging center you see this new one. Your messages can be sorted, tagged, shared, forwarded, etc. New messages are added live so you don’t have to refresh, and the whole thing just looks nice and feels clean. I don’t know how easy it is to integrate this closly to facebook, but something along these lines has to be possible.

__module_name__ = "autoactions"
__module_version__ = "1.0"
__module_description__ = "Kicks everyone when given op"

import xchat

def cm_mt(word, word_eol, userdata):
     if xchat.nickcmp(word[1], xchat.get_info('nick')) != 0:
          return xchat.EAT_NONE
     list = xchat.get_list("users")
     for i in list:
          his_nick = i.nick
          channel = xchat.get_info('channel')
          reason = "Someone made a mistake."
          if xchat.nickcmp(his_nick, word[1]) != 0:
               xchat.command("raw kick "+channel+" "+his_nick+" :"+reason)
     return xchat.EAT_NONE

xchat.hook_print("Channel Operator", cm_mt)

This script does what it says, the instant I’m given operator status on any irc channel, I automatically kick everyone else from that channel.

The thing I love here is that with a single import statement, I changed the language. Python started as a blank canvas and all I did was say, hey xchat is out there. And immediately I could call methods on xchat such as ” xchat.hook_print(“Channel Operator”, cm_mt) “.

“Nobody can know everything. But we have to work on learning by asking about the things we don’t know and listening to others. You should make a habit of learning, and of asking others about things you can’t easily know. Attempting to do something before learning about it can be dangerous.” – Açıklamalı Atasözleri Sözlüğü 1992

The message is, keep your mind open to new ideas. And that we know you can’t know everything, so we won’t think you’re an idiot when you stop and ask for directions.

This is the entry point of the application. It’s as self-explanatory as I could make it. You have decks of flashcards full of stuff to learn. You can edit a deck or learn from it.

If you click “review cards” this is what you get. (Ignore the v0.2, it’s 1.0) It shows you the first flashcards in the deck (well, it shows you a random card from one of the first 3 in the deck).

Once you push the “next button” you are instantly asked for the flashcards answer. This is meant to provide reinforcement of the card. If the card is answered incorrectly the answer is shown again, this loop continues until the card is answered correctly. When answered correctly the this card is put in an archive and a timer is set, once the timer expires the card is put in a queue of expired cards. The viewer looks for the next card to display by first looking in the queue of expired cards and then looking in the flashcard deck file.

The integral part of the program is that the timer on each card becomes longer and longer as the card is correctly answered. This provides the interactive reinforcement as described in the first post.

Here is the window that is displayed if the user chooses “Edit cards” from the main screen. Again I’ve tried to make it as easy to use as possible.

When you select a card this editing box appears. To delete a card push the “x” button. To add a card click the “Click to add new card field”. It’s self-explanatory.

On a different note, Infomatrix accepted it. I’ll be traveling to Romania soon to present a newer version of this program with an updated UI and more features.

Humans learn through repetition. The more you are exposed to something, the more likely you are to remember it, and the longer you’ll be able to remember it. Among the most effective methods of learning through repetition are flashcards. Traditionally, this is accomplished with little pieces of paper 3″x5″ that have correlating facts written on each side of them.

As computers take a bigger role in education, programs are emerging to emulate flashcards electronically. These programs typically follow the standard model of showing a card to the user, flipping it over, and repeating until all the cards have been shown. Computers can do better.

The goal of this project, “Adaptive teaching systems”, is to create a program that enhances learning by flashcards, instead of replicating it. Users are not just shown a flashcard and asked if they correctly answered it, they are expected to provide an answer. Information is given to the user and immediately asked of them, making sure it was learned. Immediate recall isn’t enough for proper retention though, so it is followed up with a spaced repetition system; As flashcards are answered correctly more and more, they are asked less and less frequently. This allows the user to learn in an effective manner.

The advantage of this system over traditional methods is that it adapts to the user. If the user quickly learns a card, it will be sent to an archive and infrequently reviewed. If the user has trouble with a particular card, it will remain in a buffer, and continually shown, until correctly answered. This allows the User to spend more of their time learning new material, as opposed to reviewing old material.