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  • How would you solve this graph theory handshake problem in python?

    - by Zachary Burt
    I graduated college last year with a degree in Psychology, but I also took a lot of math for fun. I recently got the book "Introductory Graph Theory" by Gary Chartrand to brush up on my math and have some fun. Here is an exercise from the book that I'm finding particularly befuddling: Suppose you and your husband attended a party with three other married couples. Several handshakes took place. No one shook hands with himself (or herself) or with his (or her) spouse, and no one shook hands with the same person more than once. After all the handshaking was completed, suppose you asked each person, including your husband, how many hands he or she had shaken. Each person gave a different answer. a) How many hands did you shake? b) How many hands did your husband shake? Now, I've been reasoning about this for a while, and trying to draw sample graphs that could illustrate a solution, but I'm coming up empty-handed. My logic is this: there are 8 different vertices in the graph, and 7 of them have different degrees. The values for the degrees must therefore be 0, 1, 2, 3, 4, 5, 6, and x. The # of degrees for one married couple is (0, 6). Since all graphs have an even number of odd vertices, x must be either 5, 3, or 1. What's your solution to this problem? And, if you could solve it in python, how would you do it? (python is fun.) Cheers.

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  • How would you solve this graph theory handshake problem in python?

    - by Zachary Burt
    I graduated college last year with a degree in Psychology, but I also took a lot of math for fun. I recently got the book "Introductory Graph Theory" by Gary Chartrand to brush up on my math and have some fun. Here is an exercise from the book that I'm finding particularly befuddling: Suppose you and your husband attended a party with three other married couples. Several handshakes took place. No one shook hands with himself (or herself) or with his (or her) spouse, and no one shook hands with the same person more than once. After all the handshaking was completed, suppose you asked each person, including your husband, how many hands he or she had shaken. Each person gave a different answer. a) How many hands did you shake? b) How many hands did your husband shake? Now, I've been reasoning about this for a while, and trying to draw sample graphs that could illustrate a solution, but I'm coming up empty-handed. My logic is this: there are 8 different vertices in the graph, and 7 of them have different degrees. The values for the degrees must therefore be 0, 1, 2, 3, 4, 5, 6, and x. The # of degrees for one married couple is (0, 6). Since all graphs have an even number of odd vertices, x must be either 5, 3, or 1. What's your solution to this problem? And, if you could solve it in python, how would you do it? (python is fun.) Cheers.

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  • Sorting an observable collection with linq

    - by zachary
    I have an observable collection and I sort it using linq. Everything is great, but the problem I have is how do I sort the actual observable collection? Instead I just end up with some IEnumerable thing and I end up clearing the collection and adding the stuff back in. This can't be good for performance. Does anyone know of a better way to do this?

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  • Common lisp error: "should be lambda expression"

    - by Zachary
    I just started learning Common Lisp a few days ago, and I'm trying to build a function that inserts a number into a tree. I'm getting an error, * - SYSTEM::%EXPAND-FORM: (CONS NIL LST) should be a lambda expression From googling around, it seems like this happens when you have too many sets of parenthesis, but after looking at this for an hour or so and changing things around, I can't figure out where I could be doing this. This is the code where it's happening: (defun insert (lst probe) (cond ((null lst) (cons probe lst)) ((equal (length lst) 1) (if (<= probe (first lst)) (cons probe lst) (append lst (list probe)))) ((equal (length lst) 2) ((cons nil lst) (append lst nil) (insertat nil lst 3) (cond ((<= probe (second lst)) (insert (first lst) probe)) ((> probe (fourth lst)) (insert (fifth lst) probe)) (t (insert (third lst) probe))))))) I'm pretty sure it's occurring after the ((equal (length lst) 2), where the idea is to insert an empty list into the existing list, then append an empty list onto the end, then insert an empty list into the middle.

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  • Using Taylor Series to Avoid Loss of Precision

    - by Zachary
    I'm trying to use Taylor series to develop a numerically sound algorithm for solving a function. I've been at it for quite a while, but haven't had any luck yet. I'm not sure what I'm doing wrong. The function is f(x)=1 + x - sin(x)/ln(1+x) x~0 Also: why does loss of precision even occur in this function? when x is close to zero, sin(x)/ln(1+x) isn't even close to being the same number as x. I don't see where significance is even being lost. In order to solve this, I believe that I will need to use the Taylor expansions for sin(x) and ln(1+x), which are x - x^3/3! + x^5/5! - x^7/7! + ... and x - x^2/2 + x^3/3 - x^4/4 + ... respectfully. I have attempted to use like denominators to combine the x and sin(x)/ln(1+x) components, and even to combine all three, but nothing seems to work out correctly in the end. Any help is appreciated.

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  • Using JSON input in Ruby method on Rails

    - by Zachary
    I am using jQuery to make an AJAX call to a ruby method in my controller. The javascript looks something like this: var latLongJSON = { "address": [ {"lat" : 50, "long" : 50} ] }; var returnedAddresses; $.ajax({ type: "GET", data: latLongJSON, url: "map/getaddresses", success: function(data) { returnedAddresses = JSON.parse(data); } }); Then in my 'getaddresses' method, my parameter coming through looks like: Parameters: {"address"=>"[object Object]"} I'm not sure what to do with this. I'm fairly new to Ruby, and I'm not sure if I need to convert this to something else, or what. Ideally I want to be able to pass in multiple sets of lat/long in the 'address' array, then be able to iterate over those in my Ruby code.

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  • GNU Smalltalk API?

    - by Zachary
    I have recently been learning Smalltalk, mainly by going through the tutorial at gnu.org. While it has been really helpful and I have learned a lot, I would really like an extensive smalltalk API where I could view all of the built in objects and which messages they can receive, and what they will do with those messages. The manual has a list of all of the built in objects, but doesn't really explain anything about them. Some are obvious, like an Array, but I still don't know what all the messages are an Array understands. There is a link to a 'class reference' here, which is generated by Smalltalk, but the link is broken. I was wondering if anyone knows of something like this hosted elsewhere, or could point me towards a similar resource.

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  • Building error in Eclipse with build.xml

    - by Zachary
    I am working on a Java project with Eclipse. This project requires a second project (not mine), named sams in its build-path. The sams is provided with a build.xml file and it should generate some code using Apache CXF when building it. When I use Apache ANT on Eclipse and run the cxf.generated command from its build file I get the following error: Buildfile: C:\Docs\ZacRocha\Desktop\sams\build.xml cxf.generated: [echo] Generating code using Apache CXF wsdl2java... [java] 16-Jun-2010 16:04:08 org.apache.cxf.binding.corba.CorbaConduit prepare [java] SEVERE: Could not resolve target object [java] 16-Jun-2010 16:04:08 org.apache.cxf.binding.corba.CorbaConduit prepare [java] SEVERE: Could not resolve target object [java] WSDLToJava Error: org.apache.cxf.wsdl11.WSDLRuntimeException: Fail to create wsdl definition from : file:/C:/Docs/ZacRocha/Desktop/sams/$%7barchivesoftware.wsdl%7d [java] Caused by : WSDLException: faultCode=PARSER_ERROR: Problem parsing 'file:/C:/Docs/ZacRocha/Desktop/sams/$%7barchivesoftware.wsdl%7d'.: java.io.FileNotFoundException: C:\Docs\ZacRocha\Desktop\sams\${archivesoftware.wsdl} (The system cannot find the file specified) [java] 16-Jun-2010 16:04:10 org.apache.cxf.binding.corba.CorbaConduit prepare [java] SEVERE: Could not resolve target object [java] 16-Jun-2010 16:04:10 org.apache.cxf.binding.corba.CorbaConduit prepare [java] SEVERE: Could not resolve target object [java] WSDLToJava Error: org.apache.cxf.wsdl11.WSDLRuntimeException: Fail to create wsdl definition from : file:/C:/Docs/ZacRocha/Desktop/sams/$%7barchivehardware.wsdl%7d [java] Caused by : WSDLException: faultCode=PARSER_ERROR: Problem parsing 'file:/C:/Docs/ZacRocha/Desktop/sams/$%7barchivehardware.wsdl%7d'.: java.io.FileNotFoundException: C:\Docs\ZacRocha\Desktop\sams\${archivehardware.wsdl} (The system cannot find the file specified) BUILD SUCCESSFUL Total time: 4 seconds I am used to program on Eclipse and I know very little about building with Apache ANT. Can someone tell me where exactly the problem may be? Thanks in advance!

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  • Using JSON with jRails

    - by Zachary
    I am currently trying to use AJAX in my application via jRails. I am trying to return a JSON object from my controller, and then parse it in my Javascript. I am using json2.js to do the parsing. Here is the code I currently have: function getSomething() { $.ajax({ type: "GET", url: "map/testjson", success: function(data) { var myData = JSON.parse(data[0]); window.alert(myData.login); } }); } and in the controller: class Map::MapController < ApplicationController def index end def testjson @message = User.find(:all) ActiveRecord::Base.include_root_in_json = false respond_to do |w| w.json { render :json => @message.to_json } end end end The window.alert simply says 'undefined' (without tics). However, if I change the javascript to window.alert(data) (the raw object returned by the controller) I get: [{"salt":"aSalt","name":"", "created_at":"2010-03-15T02:34:25Z","remember_token_expires_at": null,"crypted_password":"aPassword", "updated_at":"2010-03-15T02:34:25Z","id":1,"remember_token":null, "login":"zgwrig2","email":"[email protected]"}] This looks like an array of size 1, if I'm looking at it correctly, but I have tried just about every combination of JSON.parse on the data object that I can think of, and nothing seems to work. Any ideas on what I'm doing wrong here?

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  • Automatically support new changes with Python.

    - by Zachary Brown
    I was working on a program,that I need to support new additions. Hmmm. Let me give you some background on the program. It is an educational software program that has quizzes for the user to take, just to gain odd knowledge. Now, It currently supports 6 subjects, all organized with directores on the HDD ( i.e. the Science directory is called science. ) and the way you launch the subject to see what quizzes you have to take is by pushing a button on the home screen. This sort of thing prevents easy subject additions. I want to be able to add a subject later on without having to recode the home screen and re organize all the buttons. I would use a Listbox and os.listdir(...), but I was kind of wanting something prettier than a Listbox. I am using Tkinter on Windows. The Python version I am using is 2.6 Is there a "fancy" listbox sort of thing that can be styled to work with the background?

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  • Visual studio has gone crazy trying to create files

    - by zachary
    I downloaded Process Monitor and began monitoring my project directory that I am writing code in. I see endless entries every couple seconds of: Operation: Create File C:\Inetpub\wwwroot\csharp C:\Inetpub\wwwroot\code C:\Inetpub\wwwroot\web and so on for the rest of the templates Then it says the result is PATH NOT FOUND. What is happening? Has Visual Studio GONE CRAZY?!?!?!?!?!?!?!

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  • Swt combobox name/key pair

    - by zachary
    I want to have the text say one thing, but have the value say another Text Key But it only takes a string for adding items. How do Java programmers typically store text/id pairs in comboboxes

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  • Handling xml files with different structures and different names

    - by zachary
    I have a method and I want different users to pass me xml files. These files will have different names for the elements I am looking for and the elements I am looking for maybe at different structures. My first impression was that we should just tell them to pass in the xml in a standard format. However this is how they have their data and they insist that it is much easier if they don't have to convert it. What can I do to take in data of all types? Have them pass in a dictionary? number = mydata/numbers What is the easiest way for them to define their data to me without actually changing it? sample1 <numbers> 15 </numbers> sample2 <mydata> <mynumbers> 15 </mynumbers> </mydata>

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  • Free internet radio station server software with remote broadcasting?

    - by Zachary Brown
    I am in the process of creating an internet radio station, but the two djs I have for it are not able to be in one place. I need for them to be able to login to a web based broadcasting session that still has full functionality. They need to be able to broadcast thier live shows with talk and music. The music will be stroed on the server. I have checked out the Broadwave media streaming server from NCH, but ti does not have the ability to login as a dj from a remote computer. I don't have any money for this, so I need it to be free. If this is not possible, I need it to be cheap!

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  • Defining Light Coordinates

    - by Zachary
    I took a Computer Graphics exam a couple of days ago which had extra credit question like the following: A light can be defined in one of two ways. It can be defined in world coordinates, e.g. a street light, or in the viewer (eye coordinates), e.g., a head-lamp worn by a miner. In either case the viewpoint can freely change. Describe how the light should be transformed different in these two cases. Since I won't get to see the results of this until after spring break, I thought I would ask here. It seems like the analogies being used are misleading - could you not define a light source that is located at the viewers eye in world coordinates just as well as you could in eye coordinates? I've been doing some research on how OpenGL handles light, and it seems as though it always uses eye coordinates - the ModelView matrix would be applied to any light in world coordinates. In that case the answer may just be that you would have to transform light defined in world coordinates into eye coordinates using something like the ModelView matrix, while light defined in eye coordinates would only need to be transformed by the projection matrix. Then again I could be totally under thinking (or over thinking this). Another thought I had is that it determines which way you render shadows, but that has more to do with the location of the light and its type (point, directional, emission, etc) than what coordinates it is represented in. Any ideas?

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  • Allow access to my server.

    - by Zachary Brown
    I have a server, did some of the programming myself. It ison my home network, but I need to be able to access it from anywhere over the internet. I have done the port forwarding like I am supposed to, but I still cant get to it from an outside computer. It just displays Internet Explorer cannot display the webpage. I don't know what else to do. I am on a Linksys WRT54G v8 router running ddWRT v24 micro firmware.

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  • Rails user authorization

    - by Zachary
    I am currently building a Rails app, and trying to figure out the best way to authenticate that a user owns whatever data object they are trying to edit. I already have an authentication system in place (restful-authentication), and I'm using a simple before_filter to make sure a user is logged in before they can reach certain areas of the website. However, I'm not sure the best way to handle a user trying to edit a specific piece of data - for example lets say users on my site can own Books, and they can edit the properties of the book (title, author, pages, etc), but they should only be able to do this for Books that -they- own. In my 'edit' method on the books controller I would have a find that only retrieved books owned by the current_user. However, if another user knew the id of the book, they could type in http://website.com/book/7/edit , and the controller would verify that they are logged in, then show the edit page for that book (seems to bypass the controller). What is the best way to handle this? Is it more of a Rails convention routing issue that I don't understand (being able to go straight to the edit page), or should I be adding in a before_find, before_save, before_update, etc callbacks to my model?

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  • Editing remote files over SSH, using TextMate?

    - by Zachary Burt
    I LOVE using TextMate on my MacBook. It's great. Unfortunately, I want to edit some files directly on my dev server, since it's difficult to recreate the environment locally. I'm using Git, so one alternative is to just edit locally, git commit, git push, and then git merge, but that's kind of complicated every time I want to make a simple change. I'd rather just ... use another solution. One thing I tried is mounting a hard drive via MacFusion, and then loading that in an editor. But that's so freaking laggy/slow! Has anyone cooked up a better solution?

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  • How to scan convert right edges and slopes less than one?

    - by Zachary
    I'm writing a program which will use scan conversion on triangles to fill in the pixels contained within the triangle. One thing that has me confused is how to determine the x increment for the right edge of the triangle, or for slopes less than or equal to one. Here is the code I have to handle left edges with a slope greater than one (obtained from Computer Graphics: Principles and Practice second edition): for(y=ymin;y<=ymax;y++) { edge.increment+=edge.numerator; if(edge.increment>edge.denominator) { edge.x++; edge.increment -= edge.denominator; } } The numerator is set from (xMax-xMin), and the denominator is set from (yMax-yMin)...which makes sense as it represents the slope of the line. As you move up the scan lines (represented by the y values). X is incremented by 1/(denomniator/numerator) ...which results in x having a whole part and a fractional part. If the fractional part is greater than one, then the x value has to be incremented by 1 (as shown in edge.incrementedge.denominator). This works fine for any left handed lines with a slope greater than one, but I'm having trouble generalizing it for any edge, and google-ing has proved fruitless. Does anyone know the algorithm for that?

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