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  • Help me decipher this output

    - by Bragaadeesh
    Hi, I have started learning Ruby recently and I was trying out the following piece of code. a=[1,2] b='slam dunk' a.each { |b| c=a*b; puts c;} I am getting the following output. I have no clue why. I expected an error or something to be thrown. Can someone explain me why this happens? 1 2 1 2 1 2 Thanks

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  • Dijkstra's Algorithm explanation java

    - by alchemey89
    Hi, I have found an implementation for dijkstras algorithm on the internet and was wondering if someone could help me understand how the code works. Many thanks private int nr_points=0; private int[][]Cost; private int []mask; private void dijkstraTSP() { if(nr_points==0)return; //algorithm=new String("Dijkstra"); nod1=new Vector(); nod2=new Vector(); weight=new Vector(); mask=new int[nr_points]; //initialise mask with zeros (mask[x]=1 means the vertex is marked as used) for(int i=0;i<nr_points;i++)mask[i]=0; //Dijkstra: int []dd=new int[nr_points]; int []pre=new int[nr_points]; int []path=new int[nr_points+1]; int init_vert=0,pos_in_path=0,new_vert=0; //initialise the vectors for(int i=0;i<nr_points;i++) { dd[i]=Cost[init_vert][i]; pre[i]=init_vert; path[i]=-1; } pre[init_vert]=0; path[0]=init_vert; pos_in_path++; mask[init_vert]=1; for(int k=0;k<nr_points-1;k++) { //find min. cost in dd for(int j=0;j<nr_points;j++) if(dd[j]!=0 && mask[j]==0){new_vert=j; break;} for(int j=0;j<nr_points;j++) if(dd[j]<dd[new_vert] && mask[j]==0 && dd[j]!=0)new_vert=j; mask[new_vert]=1; path[pos_in_path]=new_vert; pos_in_path++; for(int j=0;j<nr_points;j++) { if(mask[j]==0) { if(dd[j]>dd[new_vert]+Cost[new_vert][j]) { dd[j]=dd[new_vert]+Cost[new_vert][j]; } } } } //Close the cycle path[nr_points]=init_vert; //Save the solution in 3 vectors (for graphical purposes) for(int i=0;i<nr_points;i++) { nod1.addElement(path[i]); nod2.addElement(path[i+1]); weight.addElement(Cost[path[i]][path[i+1]]); } }

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  • How to learn how to program?

    - by twinbornJoint
    I would like to know the best methods for learning to program. I've been directed towards the Python language because I was told it is good for beginners. I ultimately want to make games for OS X/iPhone. My problem is that I understand what I read but I can't apply my knowledge to anything. I am a programming noob. Should I stick with Python? (is there a better language I should be learning?) Where can I learn programming theory? I get very hyper when reading my book sometimes, any tips on staying calm and focusing? What are effective ways to learn how to program? Are there standard exercises for programming? (I feel solving problems helps my understanding immensely) Ultimately I feel like I am in a never ending tunnel that leads me no where. It feels like I am just completely unable to pursue anything in the world of programming, yet it is something I want to do very much. Thanks.

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  • More ruby-like solution to this problem?

    - by RaouL
    I am learning ruby and practicing it by solving problems from Project Euler. This is my solution for problem 12. # Project Euler problem: 12 # What is the value of the first triangle number to have over five hundred divisors? require 'prime' triangle_number = ->(num){ (num *(num + 1)) / 2 } factor_count = ->(num) do prime_fac = Prime.prime_division(num) exponents = prime_fac.collect { |item| item.last + 1 } fac_count = exponents.inject(:*) end n = 2 loop do tn = triangle_number.(n) if factor_count.(tn) >= 500 puts tn break end n += 1 end Any improvements that can be made to this piece of code?

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  • Any difference in compiler behavior for each of these snippets?

    - by HotHead
    Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } What compiler does in backgorund and what is the best (and correct) way to do above testing? p.s. sorry, but I couldn't find the better title :) EDIT: values 0x0001 and 0x0002 are only example. There coudl be any 2 byte value instead. Thank you in advance!

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  • Condensing multiple else if statements, referencing them from a table?

    - by Haskella
    Hi I'm about to type some 500 else if statements into my code (PHP) which have the exact same coding each: if (color=White); rgb = 255-255-255; print rgb; else if (color=Black); rgb = 0-0-0; print rgb; else if (color=Red); rgb = 255-0-0; print rgb; else if (color=Blue); rgb = 0-0-255; print rgb; [the list keeps going] I also (luckily) have a table that displays the color in the first column and rgb value in the next column for 500 of them... how do I use this to save time typing all those else if statements? Some how I have to reference the table file (made in excel, I'm guessing I'll have to save it as .csv?)

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  • Asp.net webservices

    - by Patel
    Hi everyone, I am new to asp.net .. i want to learn about web services.. can anyone pls provide me a good link or pdf on web services for reading it from basic.. thanks in advance..

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  • How to deal with clients and iterations in Agile team?

    - by Ondrej Slinták
    This thread is a follow up to my previous one. It's in fact 2 questions, so I hope no one minds, as they are dependent on each other. We are starting a new project at work and we consider it as a great opportunity to try Agile techniques in action. We had a brainstorming about ideas we read in several books and articles, and came up with concept that would suit us the best: 2 weeks iteration, followed by call with clients who would choose what stuff they want to have in next iteration. I just have few more questions, which we couldn't figure out ourselves. What to do in the first iteration? What to, generally, do in the first few iterations if we start from the scratch? Just give it a month of development to code core of the application or start with simple wire-frames with limited pre-coded functionality? What usually clients want to see? Shiny stuff that doesn't work or ugly stuff that does work? How to communicate with clients? Our initial thought it to set the process to something like this: Is it a good idea to have a Focal Point on client side or is it better to communicate straight with all the clients to prevent miscommunication? Any thoughts are welcome! Thanks in advance.

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  • How do I use Mercurial?

    - by Derek
    I'm assuming Mercurial is for having an updated website and it archiving the old stuff? Easy to test things and such? My question is, how exactly should I get started and can somebody give me a crash course in using Mercurial and using the following techs below: Notepad++ for coding FTP PHP/MySQL Jquery & other js libraries I use windows and would like to keep things fairly simple. I'm developing 1 website currently and want some kind of CVS system in place. Or should I just stick to my current edit file in notepad++ and upload via ftp method and make a backup copy of everything every once and a while? Any thoughts? EDIT: I'm doing http://bugtracker.gttools.com/public/wiki/bluehost/Mercurial right now in order to try and 'install' it.

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  • I need to speed up a function. Should I use cython, ctypes, or something else?

    - by Peter Stewart
    I'm having a lot of fun learning Python by writing a genetic programming type of application. I've had some great advice from Torsten Marek, Paul Hankin and Alex Martelli on this site. The program has 4 main functions: generate (randomly) an expression tree. evaluate the fitness of the tree crossbreed mutate As all of generate, crossbreed and mutate call 'evaluate the fitness'. it is the busiest function and is the primary bottleneck speedwise. As is the nature of genetic algorithms, it has to search an immense solution space so the faster the better. I want to speed up each of these functions. I'll start with the fitness evaluator. My question is what is the best way to do this. I've been looking into cython, ctypes and 'linking and embedding'. They are all new to me and quite beyond me at the moment but I look forward to learning one and eventually all of them. The 'fitness function' needs to compare the value of the expression tree to the value of the target expression. So it will consist of a postfix evaluator which will read the tree in a postfix order. I have all the code in python. I need advice on which I should learn and use now: cython, ctypes or linking and embedding. Thank you.

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  • What is the typical method to separate connected letters in a word using OCR

    - by Maysam
    I am very new to OCR and almost know nothing about the algorithms used to recognize words. I am just getting familiar to that. Could anybody please advise on the typical method used to recognize and separate individual characters in connected form (I mean in a word where all letters are linked together)? Forget about handwriting, supposing the letters are connected together using a known font, what is the best method to determine each individual character in a word? When characters are written separately there is no problem, but when they are joined together, we should know where every single character starts and ends in order to go to the next step and match them individually with a letter. Is there any known algorithm for that?

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  • jQuery: Moving window (or FIFO) type DIV?

    - by Legend
    I have been trying to get this effect for a couple of hours now and I must admit I am failing at it. I am trying to construct a DIV that accepts a particular number of items (say 5), when the 6th item is added, the first item that was aded should be removed (first-in-first-out). The feel should have some kind of a fadeIn and fadeOut. Here's what I managed to write till now: ... //Create a ul element with id 'ulele' and add it to a div ... //Do an ajax call and when an element arrives Hash = ComputeHash(message) if(!$("#" + Hash).exists()) { var element = $("<li></li>").html(message).attr('id', Hash).prependTo("#ulele"); $("#" + Hash).hide().delay(10000 - 1000 * messageNumber).show("slow"); _this.prune("#ulele"); } ... prune: function(divid) { $("#" + divid).children().each( function(i, elemLi) { if(i >= maxMessages) $(this).delay(10000).hide("slow").delay(10000).remove(); } ); } I've tried a couple of variations but the final effect I am getting is not that of a FIFO. The elements disappear instantaneously despite the delay and hide("slow") calls. Anyone has a more straightforward approach?

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  • Using GA in GUI

    - by AlexT
    Sorry if this isn't clear as I'm writing this on a mobile device and I'm trying to make it quick. I've written a basic Genetic Algorithm with a binary encoding (genes) that builds a fitness value and evolves through several iterations using tournament selection, mutation and crossover. As a basic command-line example it seems to work. The problem I've got is with applying a genetic algorithm within a GUI as I am writing a maze-solving program that uses the GA to find a method through a maze. How do I turn my random binary encoded genes and fitness function (add all the binary values together) into a method to control a bot around a maze? I have built a basic GUI in Java consisting of a maze of labels (like a grid) with the available routes being in blue and the walls being in black. To reiterate my GA performs well and contains what any typical GA would (fitness method, get and set population, selection, crossover, etc) but now I need to plug it into a GUI to get my maze running. What needs to go where in order to get a bot that can move in different directions depending on what the GA says? Rough pseudocode would be great if possible As requested, an Individual is built using a separate class (Indiv), with all the main work being done in a Pop class. When a new individual is instantiated an array of ints represent the genes of said individual, with the genes being picked at random from a number between 0 and 1. The fitness function merely adds together the value of these genes and in the Pop class handles selection, mutation and crossover of two selected individuals. There's not much else to it, the command line program just shows evolution over n generations with the total fitness improving over each iteration. EDIT: It's starting to make a bit more sense now, although there are a few things that are bugging me... As Adamski has suggested I want to create an "Agent" with the options shown below. The problem I have is where the random bit string comes into play here. The agent knows where the walls are and has it laid out in a 4 bit string (i.e. 0111), but how does this affect the random 32 bit string? (i.e. 10001011011001001010011011010101) If I have the following maze (x is the start place, 2 is the goal, 1 is the wall): x 1 1 1 1 0 0 1 0 0 1 0 0 0 2 If I turn left I'm facing the wrong way and the agent will move completely off the maze if it moves forward. I assume that the first generation of the string will be completely random and it will evolve as the fitness grows but I don't get how the string will work within a maze. So, to get this straight... The fitness is the result of when the agent is able to move and is by a wall. The genes are a string of 32 bits, split into 16 sets of 2 bits to show the available actions and for the robot to move the two bits need to be passed with four bits from the agent showings its position near the walls. If the move is to go past a wall the move isn't made and it is deemed invalid and if the move is made and if a new wall is found then the fitness goes up. Is that right?

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  • Efficient way in Python to add an element to a comma-separated string

    - by ensnare
    I'm looking for the most efficient way to add an element to a comma-separated string while maintaining alphabetical order for the words: For example: string = 'Apples, Bananas, Grapes, Oranges' addition = 'Cherries' result = 'Apples, Bananas, Cherries, Grapes, Oranges' Also, a way to do this but while maintaining IDs: string = '1:Apples, 4:Bananas, 6:Grapes, 23:Oranges' addition = '62:Cherries' result = '1:Apples, 4:Bananas, 62:Cherries, 6:Grapes, 23:Oranges' Sample code is greatly appreciated. Thank you so much.

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  • Blogger Template: how to change the color of the border css

    - by Lirik
    Hi, I'm trying to change the borders in the style sheet of the template on my blog, but I've never done anything with css so I'm a little bit at a loss... I want to keep the dark background, but I want to create a small border with a slightly different color around my postings. If my guess is correct, then I should modify some of these definitions: body { background:$bgcolor; margin:0; color:$textcolor; font: x-small "Trebuchet MS", Trebuchet, Verdana, Sans-serif; font-size/* */:/**/small; font-size: /**/small; text-align: center; } a:link { color:$linkcolor; text-decoration:none; } a:visited { color:$visitedlinkcolor; text-decoration:none; } a:hover { color:$titlecolor; text-decoration:underline; } a img { border-width:0; } Here is a pastie with the entire template I'm using: http://pastie.org/932535 Is there a quick way to achieve the desired effect? Your help is appreciated!

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  • Is using the break statement bad practice?

    - by Lchi
    I've been told by professors and peers at my university that using the break statement is bad practice, but through my coursework haven't come up with a great reason why. Those who claim that it is bad say that it's a "get out of jail free card" and that you can always avoid using it. My guesses for why its considered bad would be that you could possibly skip some cleanup code after the break, or similarly exit some control structure in an inconsistent state. Is there any reason why using break is(n't) bad practice?

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  • Form to sort an index in rails

    - by shmichael
    I'm a newcomer to Rails. I want to build a simple form that determines the sort order of a list. I've implemented a form in the likes of - <%= radio_button_tag :sort, "rating" %> <%= label_tag :sort_rating, "order by rating" %> <%= radio_button_tag :sort, "name" %> <%= label_tag :sort_name, "order by name" %> And now I am unsure how to implement the sort at the controller/model level. The aspects I am puzzled about are: Where should the sort be performed How could the sort parameter be persisted How could the code be reused Right now, I can't even get the selected sort method to remain selected after a submit. I would most appreciate any guidance or reference to an example.

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  • how to send an array of bytes over a TCP connection (java programming)

    - by Mark Roberts
    Can somebody demonstrate how to send an array of bytes over a TCP connection from a sender program to a receiver program in Java. (I'm new to Java programming, and can't seem to find an example of how to do this that shows both ends of the connection (sender and receiver.) If you know of an existing example, maybe you could post the link. (No need to reinvent the wheel.) P.S. This is NOT homework! :-)

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  • Getting unpredictable data into a tabular format

    - by Acorn
    The situation: Each page I scrape has <input> elements with a title= and a value= I don't know what is going to be on the page. I want to have all my collected data in a single table at the end, with a column for each title. So basically, I need each row of data to line up with all the others, and if a row doesn't have a certain element, then it should be blank (but there must be something there to keep the alignment). eg. First page has: {animal: cat, colour: blue, fruit: lemon, day: monday} Second page has: {animal: fish, colour: green, day: saturday} Third page has: {animal: dog, number: 10, colour: yellow, fruit: mango, day: tuesday} Then my resulting table should be: animal | number | colour | fruit | day cat | none | blue | lemon | monday fish | none | green | none | saturday dog | 10 | yellow | mango | tuesday Although it would be good to keep the order of the title value pairs, which I know dictionaries wont do. So basically, I need to generate columns from all the titles (kept in order but somehow merged together) What would be the best way of going about this without knowing all the possible titles and explicitly specifying an order for the values to be put in?

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  • Can not install Ubuntu 12.04 or 12.10 on Toshiba qosmio x870. Please help!

    - by Mighty
    I have a new Toshiba qosmio x870 and for the past one week I have been trying to install Ubuntu 12.04 from a USB and Live CD without success. I keep on getting this error: Boot failure: a proper digital signature was not found. One or more files on the selected boot device was rejected by the Secure Boot feature. I even tried installing Ubuntu with the Windows installer. After installation and I reboot the PC, first I see the error that points to: \ubuntu\winboot\wubildr.mbr Status: 0xc000007b Info: The OS couldn't be loaded because a required file is missing or contains errors. When I restart, that the previous error doesn't show up and I see both Windows 8 and Ubuntu (happy that I was successful) but when I click on Ubuntu, it flags an error. This is the first time I'm having a Secure Boot-capable PC. What will be the danger in disabling the secure boot? I'll be happy if I can get assistance from anyone.

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