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  • how to get access to private members of nested class?

    - by macias
    Background: I have enclosed (parent) class E with nested class N with several instances of N in E. In the enclosed (parent) class I am doing some calculations and I am setting the values for each instance of nested class. Something like this: n1.field1 = ...; n1.field2 = ...; n1.field3 = ...; n2.field1 = ...; ... It is one big eval method (in parent class). My intention is -- since all calculations are in parent class (they cannot be done per nested instance because it would make code more complicated) -- make the setters only available to parent class and getters public. And now there is a problem: when I make the setters private, parent class cannot acces them when I make them public, everybody can change the values and C# does not have friend concept I cannot pass values in constructor because lazy evaluation mechanism is used (so the instances have to be created when referencing them -- I create all objects and the calculation is triggered on demand) I am stuck -- how to do this (limit access up to parent class, no more, no less)? I suspect I'll get answer-question first -- "but why you don't split the evaluation per each field" -- so I answer this by example: how do you calculate min and max value of a collection? In a fast way? The answer is -- in one pass. This is why I have one eval function which does calculations and sets all fields at once.

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  • count how many days within a date range are within another date range

    - by joko13
    From October 1st to March 31 the fee is $1 (season 1). From April 1st to September 30 the fee is $2 (season 2). How can I calculate the total fee of a given date range (user input) depending on how many days of this date range fall into season 1 and season 2? The following gives me the number of days of the user´s date range, but I have no idea how to test against season 1 or season 2: $user_input_start_date = getdate( $a ); $user_input_end_date = getdate( $b ); $start_date_new = mktime( 12, 0, 0, $user_input_start_date['mon'], $user_input_start_date['mday'], $user_input_start_date['year'] ); $end_date_new = mktime( 12, 0, 0, $user_input_end_date['mon'], $user_input_end_date['mday'], $user_input_end_date['year'] ); return round( abs( $start_date_new - $end_date_new ) / 86400 ); Thanks for your help! EDIT: Given that a date range starts and ends in 2012 or starts in 2012 and ends in 2013 alone gives me 10 different possibilities of in which season a date range can start and where it can end. There must be a better solution than iterating if/else and comparing dates over and over again for the following conditions: Date range is completely within season 1 Date range starts in season 1 and ends in season 2 Date range starts in season 1, spans across season 2 and ends in the second part of season 1 ... and so forth with "Starts in season 2", etc

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  • Jqyery Bugs?? Long decimal number after two numbers multiply...

    - by Jerry
    Hi all I am working on a shopping site and I am trying to calculate the subtotal of products. I got my price from a array and quantity from getJSON response array. Two of them multiply comes to my subtotal. I can change the quantity and it will comes out different subtotal. However,when I change the quantity to certain number, the final subtotal is like 259.99999999994 or some long decimal number. I use console.log to check the $price and $qty. Both of them are in the correct format ex..299.99 and 6 quantity.I have no idea what happen. I would appreciate it if someone can help me about it. Here is my Jquery code. $(".price").each(function(index, price){ $price=$(this); //get the product id and the price shown on the page var id=$price.closest('tr').attr('id'); var indiPrice=$($price).html(); //take off $ indiPrice=indiPrice.substring(1) //make sure it is number format var aindiPrice=Number(indiPrice); //push into the array productIdPrice[id]=(aindiPrice); var url=update.php $.getJSON( url, {productId:tableId, //tableId is from the other jquery code which refers to qty:qty}, productId function(responseProduct){ $.each(responseProduct, function(productIndex, Qty){ //loop the return data if(productIdPrice[productIndex]){ //get the price from the previous array we create X Qty newSub=productIdPrice[productIndex]*Number(Qty); //productIdPrice[productIndex] are the price like 199.99 or 99.99 // Qty are Quantity like 9 or 10 or 3 sum+=newSub; newSub.toFixed(2); //try to solve the problem with toFixed but didn't work console.log("id: "+productIdPrice[productIndex]) console.log("Qty: "+Qty); console.log(newSub); **//newSub sometime become XXXX.96999999994** }; Thanks again!

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  • Getting a handle on GIS math, where do I start?

    - by Joshua
    I am in charge of a program that is used to create a set of nodes and paths for consumption by an autonomous ground vehicle. The program keeps track of the locations of all items in its map by indicating the item's position as being x meters north and y meters east of an origin point of 0,0. In the real world, the vehicle knows the location of the origin's lat and long, as it is determined by a dgps system and is accurate down to a couple centimeters. My program is ignorant of any lat long coordinates. It is one of my goals to modify the program to keep track of lat long coords of items in addition to an origin point and items' x,y position in relation to that origin. At first blush, it seems that I am going to modify the program to allow the lat long coords of the origin to be passed in, and after that I desire that the program will automatically calculate the lat long of every item currently in a map. From what I've researched so far, I believe that I will need to figure out the math behind converting to lat long coords from a UTM like projection where I specify the origin points and meridians etc as opposed to whatever is defined already for UTM. I've come to ask of you GIS programmers, am I on the right track? It seems to me like there is so much to wrap ones head around, and I'm not sure if the answer isn't something as simple as, "oh yea theres a conversion from meters to lat long, here" Currently, due to the nature of DGPS, the system really doesn't need to care about locations more than oh, what... 40 km? radius away from the origin. Given this, and the fact that I need to make sure that the error on my coordinates is not greater than .5 meters, do I need anything more complex than a simple lat/long to meters conversion constant? I'm knee deep in materials here. I could use some pointers about what concepts to research. Thanks much!

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  • Trying to draw a dynamic rectangle in SVG

    - by Shaun
    To be more specific, here are the steps I need: onmousedown - set x and y of rect as mouse coordinates onmousemove - using the current x and y mouse coordinates calculate height and width of the rect, set these and append onmouseup - remove the rectangle, and call a function based off some calculations from the rect. Here is what I have but isn't quite working (right now I have it drawing a line to make it simpler): onmousedown: startbox(evt) function startbox(evt) { if(evt.button === 0) { x1 = evt.clientX + div.scrollLeft-5; y1 = evt.clientY + div.scrollTop-30; obj.setAttributeNS(null, "x1", x1); obj.setAttributeNS(null, "y1", y1); Root.setAttributeNS(null, "onmousemove", "updatebox(evt)"); } } onmousemove: updatebox(evt) function updatebox(evt) { if(evt.button === 0) { x2 = evt.clientX + div.scrollLeft-5; y2 = evt.clientY + div.scrollTop-30; Root.appendChild(.obj); w = Math.abs(x2-x1); h = Math.abs(y2-y1); var strokecolor; if(w>20 && h>20) { strokecolor = "green"; validbox = true; } else { strokecolor = "red"; validbox = false; } var Attr={ x2:x2, y2:y2, stroke:strokecolor } assignAttr(obj, Attr); //just loops thru adding multiple attributes } } onmouseup: endbox() function endbox(evt) { if(evt.button===0) { Root.setAttributeNS(null, "onmousemove", ""); Root.removeChild(obj); if(validbox) { //do stuff validbox = !validbox; } } } Some of my problems with this are: Its slow in Chrome making drawing the line/rect feel sluggish. It won't work two times in a row. This is the real problem that I can't fix. Any and all feedback is welcome.

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  • What is wrong with this recursive Windows CMD script? It won't do Ackermann properly

    - by boost
    I've got this code that I'm trying to get to calculate the Ackermann function so that I can post it up on RosettaCode. It almost works. I thought maybe there'd be a few batch file wizards on StackOverflow. ::echo off set depth=0 :ack if %1==0 goto m0 if %2==0 goto n0 :else set /a n=%2-1 set /a depth+=1 call :ack %1 %n% set t=%errorlevel% set /a depth-=1 set /a m=%1-1 set /a depth+=1 call :ack %m% %t% set t=%errorlevel% set /a depth-=1 if %depth%==0 ( exit %t% ) else ( exit /b %t% ) :m0 set/a n=%2+1 if %depth%==0 ( exit %n% ) else ( exit /b %n% ) :n0 set /a m=%1-1 set /a depth+=1 call :ack %m% %2 set t=%errorlevel% set /a depth-=1 if %depth%==0 ( exit %t% ) else ( exit /b %t% ) I use this script to test it @echo off cmd/c ackermann.cmd %1 %2 echo Ackermann of %1 %2 is %errorlevel% A sample output, for Test 1 1, gives: >test 1 1 >set depth=0 >if 1 == 0 goto m0 >if 1 == 0 goto n0 >set /a n=1-1 >set /a depth+=1 >call :ack 1 0 >if 1 == 0 goto m0 >if 0 == 0 goto n0 >set /a m=1-1 >set /a depth+=1 >call :ack 0 0 >if 0 == 0 goto m0 >set/a n=0+1 >if 2 == 0 (exit 1 ) else (exit /b 1 ) >set t=1 >set /a depth-=1 >if 1 == 0 (exit 1 ) else (exit /b 1 ) >set t=1 >set /a depth-=1 >set /a m=1-1 >set /a depth+=1 >call :ack 0 1 >if 0 == 0 goto m0 >set/a n=1+1 >if 1 == 0 (exit 2 ) else (exit /b 2 ) >set t=2 >set /a depth-=1 >if 0 == 0 (exit 2 ) else (exit /b 2 ) Ackermann of 1 1 is 2

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  • What is wrong with accessing DBI directly?

    - by canavanin
    Hi everyone! I'm currently reading Effective Perl Programming (2nd edition). I have come across a piece of code which was described as being poorly written, but I don't yet understand what's so bad about it, or how it should be improved. It would be great if someone could explain the matter to me. Here's the code in question: sub sum_values_per_key { my ( $class, $dsn, $user, $password, $parameters ) = @_; my %results; my $dbh = DBI->connect( $dsn, $user, $password, $parameters ); my $sth = $dbh->prepare( 'select key, calculate(value) from my_table'); $sth->execute(); # ... fill %results ... $sth->finish(); $dbh->disconnect(); return \%results; } The example comes from the chapter on testing your code (p. 324/325). The sentence that has left me wondering about how to improve the code is the following: Since the code was poorly written and accesses DBI directly, you'll have to create a fake DBI object to stand in for the real thing. I have probably not understood a lot of what the book has so far been trying to teach me, or I have skipped the section relevant for understanding what's bad practice about the above code... Well, thanks in advance for your help!

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  • Animating translation and scaling of view in Android

    - by hgpc
    I have to animate a view from state A to B with changes to its scale, position and scrolling. I know everything about state A (widthA, heightA, topA, leftA, scrollXA, scrollYA) and state B (widthB, heightB, topB, leftB, scrollXB, scrollYB). So far I wrote the following code: AnimationSet animation = new AnimationSet(true); int toXDelta; // What goes here? int toYDelta; // What goes here? TranslateAnimation translateAnimation = new TranslateAnimation(1, toXDelta, 1, toYDelta); translateAnimation.setDuration(duration); animation.addAnimation(translateAnimation); float scale = (float) widthB / (float) widthA; ScaleAnimation scaleAnimation = new ScaleAnimation(1, scale, 1, scale); scaleAnimation.setDuration(duration); animation.addAnimation(scaleAnimation); animation.setAnimationListener(new AnimationListener() { @Override public void onAnimationEnd(Animation arg0) { view.clearAnimation(); // Change view to state B } @Override public void onAnimationRepeat(Animation arg0) {} @Override public void onAnimationStart(Animation arg0) {} }); view.startAnimation(animation); Is this the right way to do this? If so, how should I calculate the values of toXDelta and toYDelta? I'm having trouble finding the exact formula. Thanks!

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  • Android - Read PNG image without alpha and decode as ARGB_8888

    - by loki666
    I try to read an image from sdcard (in emulator) and then create a Bitmap image with the BitmapFactory.decodeByteArray method. I set the options: options.inPrefferedConfig = Bitmap.Config.ARGB_8888 options.inDither = false Then I extract the pixels into a ByteBuffer. ByteBuffer buffer = ByteBuffer.allocateDirect(width*height*4) bitmap.copyPixelsToBuffer(buffer) I use this ByteBuffer then in the JNI to convert it into RGB format and want to calculate on it. But always I get false data - I test without modifying the ByteBuffer. Only thing I do is to put it into the native method into JNI. Then cast it into a unsigned char* and convert it back into a ByteBuffer before returning it back to Java. unsigned char* buffer = (unsinged char*)(env->GetDirectBufferAddress(byteBuffer)) jobject returnByteBuffer = env->NewDirectByteBuffer(buffer, length) Before displaying the image I get data back with bitmap.copyPixelsFromBuffer( buffer ) But then it has wrong data in it. My Question is if this is because the image is internally converted into RGB 565 or what is wrong here? ..... Have an answer for it: - yes, it is converted internally to RGB565. Does anybody know how to create such an bitmap image from PNG with ARGB8888 pixel format? If anybody has an idea, it would be great!

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  • DSP - Filter sweep effect

    - by Trap
    I'm implementing a 'filter sweep' effect (I don't know if it's called like that). What I do is basically create a low-pass filter and make it 'move' along a certain frequency range. To calculate the filter cut-off frequency at a given moment I use a user-provided linear function, which yields values between 0 and 1. My first attempt was to directly map the values returned by the linear function to the range of frequencies, as in cf = freqRange * lf(x). Although it worked ok it looked as if the sweep ran much faster when moving through low frequencies and then slowed down during its way to the high frequency zone. I'm not sure why is this but I guess it's something to do with human hearing perceiving changes in frequency in a non-linear manner. My next attempt was to move the filter's cut-off frequency in a logarithmic way. It works much better now but I still feel that the filter doesn't move at a constant perceived speed through the range of frequencies. How should I divide the frequency space to obtain a constant perceived sweep speed? Thanks in advance.

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  • Simple encryption - Sum of Hashes in C

    - by Dogbert
    I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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  • OPTICS Clustering algorithm. How to get the best epsilon

    - by Marco Galassi
    I am implementing a project which needs to cluster geographical points. OPTICS algorithm seems to be a very nice solution. It needs just 2 parameters as input(MinPts and Epsilon), which are, respectively, the minimum number of points needed to consider them as a cluster, and the distance value used to compare if two points are in can be placed in same cluster. My problem is that, due to the extreme variety of the points, I can't set a fixed epsilon. Just look at the image below. The same points structure but in a different scale would result very different. Suppose to set MinPts=2 and epsilon = 1Km. On the left, the algorithm would create 2 clusters(red and blue), but on the right it would create one single cluster containing all of the points(red), but I would like to obtain 2 clusters even on the right. So my question is: is there any kind of way to calculate dynamically the epsilon value to get this result? Thank you very much and excuse my for my poor english. Marco

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  • Android Compass orientation on unreliable (Low pass filter)

    - by madsleejensen
    Hi all Im creating an application where i need to position a ImageView depending on the Orientation of the device. I use the values from a MagneticField and Accelerometer Sensors to calculate the device orientation with SensorManager.getRotationMatrix(rotationMatrix, null, accelerometerValues, magneticFieldValues) SensorManager.getOrientation(rotationMatrix, values); double degrees = Math.toDegrees(values[0]); My problem is that the positioning of the ImageView is very sensitive to changes in the orientation. Making the imageview constantly jumping around the screen. (because the degrees change) I read that this can be because my device is close to things that can affect the magneticfield readings. But this is not the only reason it seems. I tried downloading some applications and found that the "3D compass" application remains extremely steady in its readings, i would like the same behavior in my application. I read that i can tweak the "noise" of my readings by adding a "Low pass filter", but i have no idea how to implement this (because of my lack of Math). Im hoping someone can help me creating a more steady reading on my device, Where a little movement to the device wont affect the current orientation. Right now i do a small if (Math.abs(lastReadingDegrees - newReadingDegrees) > 1) { updatePosition() } To filter abit of the noise. But its not working very well :)

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  • NHibernate complex order query

    - by manu08
    Here's my simplified domain public class Notification { public Guid ID { get; set; } public string Name { get; set; } public IEnumerable<Location> Locations { get; set; } } public class Location { public Guid Id { get; set; } public string Name { get; set; } public decimal Longitude { get; set; } public decimal Latitude { get; set; } } Notifications and Locations have a many-to-many relationship (defined in table LocationsOnNotification). What I'd like to do is query for the nearest 10 Notifications from a given longitude and latitude. I've been trying to use ICriteria, but I'm not sure how to specify the ordering correctly: return Session.CreateCriteria<Notification>() .SetFirstResult(firstIndex) .SetMaxResults(maxResults) .AddOrder(Order.Asc( WHAT GOES HERE! )) .List<Notification>(); What I've been thinking of so far is adding a formula property to the Location mapping; something like this: <property name='Distance' formula='lots of geometry'/> But I'm not sure if that can take in parameters (since I'd need to pass in the user's location to calculate the distance), plus I'm not sure how to specify it in the Order.Asc clause given that it's a property on a many-to-many association class. Any ideas? Or perhaps I should take a different approach altogether. Thanks in advance!

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  • Implementing a scrabble trainer

    - by bstullkid
    Hello, I've recently been playing alot of online scrabble so I decided to make a program that quickly searches through a dictionary of 200,000+ words with an input of up to any 26 letters. My first attempt was fail as it took a while when you input 8 or more letters (just a basic look through dictionary and cancel out a letter if its found kind of thing), so I made a tree like structure containing only an array of 26 of the same structure and a flag to indicate the end of a word, doing that It can output all possible words in under a second even with an input of 26 characters. But it seems that when I input 12 or more letters with some of the same characters repeated i get duplicates; can anyone see why I would be getting duplicates with this code? (ill post my program at the bottom) Also, the next step once the duplicates are weeded out is to actually be able to input the letters on the game board and then have it calculate the best word you can make on a given board. I am having trouble trying to figure out a good algorithm that can analyze a scrabble board and an input of letters and output a result; the possible words that could be made I have no problem with but actually checking a board efficiently (ie can this word fit here, or here etc... without creating a non dictionary word in the process on some other string of letters) Anyone have a idea for an approach at that? (given a scrabble board, and an input of 7 letters, find all possible valid words or word sets that you can make) lol crap i forgot to email myself the code from my other computer thats in another state... ill post it on monday when I get back there! btw the dictionary im using is sowpods (http://www.calvin.edu/~rpruim/scrabble/ospd3.txt)

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  • Retrieving license type (linux/windows/windows+sqlserver) for an Amazon EC2 instance via the API?

    - by Geir
    I need to calculate the hourly running costs for my Amazon EC2 instances. This varies even between instances with same hardware configs (instance types) because I use different amazon images (AMIs): some plain windows server and some windows server with sql server (both of them have additional costs compared with plain linux instances) The EC2 Java API has a describeInstances() method which returns Instance objects with metadata such as instance id, instance type (m1.small/large...), state (running,stopped..) public ip, etc. This Instance object also has a .getLicense().getPool() which according to the Java API should return "The license pool from which this license was used (ex: 'windows')." I thought this is were it may also give 'windows+sqlserver' or something to that effect. The getLicense() method does however return null.. I've navigated around the EC2 web console, not being able to find this information, but I'm hoping that it is possible - otherwise it would mean that you cannot identify the true hourly cost of an particular instance unless you know which AMI was used to create it in the first place (plain windows server or windows server with sql server). Anyone? Thanks :) /Geir

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  • I can't read the value from a radio button.

    - by Corey
    <html> <head> <title>Tip Calculator</title> <script type="text/javascript"><!-- function calculateBill(){ var check = document.getElementById("check").value; /* I try to get the value selected */ var tipPercent = document.getElementById("tipPercent").value; /* But it always returns the value 15 */ var tip = check * (tipPercent / 100) var bill = 1 * check + tip; document.getElementById('bill').innerHTML = bill; } --></script> </head> <body> <h1 style="text-align:center">Tip Calculator</h1> <form id="f1" name="f1"> Average Sevice: 15%<input type="radio" id="tipPercent" name="tipPercent" value="15" /> <br /> Excellent Sevice: 20%<input type="radio" id="tipPercent" name="tipPercent" value="20" /> <br /><br /> <label>Check Amount</label> <input type="text" id="check" size="10" /> <input type="button" onclick="calculateBill()" value="Calculate" /> </form> <br /> Total Bill: <p id="bill"></p> </body> </html>

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  • MATLAB setting matrix values in an array

    - by user324994
    I'm trying to write some code to calculate a cumulative distribution function in matlab. When I try to actually put my results into an array it yells at me. tempnum = ordered1(1); k=2; while(k<538) count = 1; while(ordered1(k)==tempnum) count = count + 1; k = k + 1; end if(ordered1(k)~=tempnum) output = [output;[(count/537),tempnum]]; k = k + 1; tempnum = ordered1(k); end end The errors I'm getting look like this ??? Error using ==> vertcat CAT arguments dimensions are not consistent. Error in ==> lab8 at 1164 output = [output;[(count/537),tempnum]]; The line to add to the output matrice was given to me by my TA. He didn't teach us much syntax throughout the year so I'm not really sure what I'm doing wrong. Any help is greatly appreciated.

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  • How can I read the value of a radio button in JavaScript?

    - by Corey
    <html> <head> <title>Tip Calculator</title> <script type="text/javascript"><!-- function calculateBill(){ var check = document.getElementById("check").value; /* I try to get the value selected */ var tipPercent = document.getElementById("tipPercent").value; /* But it always returns the value 15 */ var tip = check * (tipPercent / 100) var bill = 1 * check + tip; document.getElementById('bill').innerHTML = bill; } --></script> </head> <body> <h1 style="text-align:center">Tip Calculator</h1> <form id="f1" name="f1"> Average Service: 15% <input type="radio" id="tipPercent" name="tipPercent" value="15" /> <br /> Excellent Service: 20% <input type="radio" id="tipPercent" name="tipPercent" value="20" /> <br /><br /> <label>Check Amount</label> <input type="text" id="check" size="10" /> <input type="button" onclick="calculateBill()" value="Calculate" /> </form> <br /> Total Bill: <p id="bill"></p> </body> </html> I try to get the value selected with document.getElementById("tipPercent").value, but it always returns the value 15.

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  • Deep Zoom in Ajax - Possible? Any examples out there?

    - by Phil
    I have an idea to implement a deep zoom type interface hosted in a browser for sports training data (speed, distance, heart rate etc.) However, rather than images I actually want to zoom into a hierarchy of information. For example, the initial display would contain a grid of years - hover over 2008, for example, and spin the mouse wheel (or click) will zoom into that year but during the zoom I want 2008 to fade out and be replaced with a calendar of months. Again zoom into a month and the months are replaced with the months calendar, zoom into a day and you finally see a chart with the training data plotted on it. All the time only dates with actual data would be highlighted in some fashion. My question is whether this would even be possible and whether anyone has seen examples of this already. I'm imagining that most of the time the next level of information could be cached in the browser (in fact, because this is calendar-based, I can calculate most of that and cache the dates to be highlighted.) I could also zoom into an empty chart whilst an Ajax thread is fetching the data to display. I've never tried anything like this before and I'm especially interested in whether DHTML would be capable of this sort of zoom (I suspect not and I would have to resort to Silverlight) and whether the Ajax execution would be uninterrupted whilst the browser rendering thread is kept busy zooming.

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  • The mathematics of Schellings segregation model

    - by Bruce
    For those who don't know the model. You can read this pdf. I want to find what is the probability that 2 nodes are each others neighbors when the algorithm converges (i.e. when all nodes are happy). Here's the model in a gist. You have a grid (say 10x10). You have nodes of two kind (red and green) 45 each. So we have 10 empty spaces. We randomly place the nodes on the grid. Now we scan through this grid (Exact order does not matter according to Schelling). Each node wants a specific percentage of people of same kind in its Moore neighborhood (say b = 50% for each red and green). We calculate the happiness of each node (a = Number of neighbors of same kind/Number of neighbors of different kind). If a node is unhappy (a < b) it moves to an empty cell where it knows it will be happy. This movement can change the dynamics of old as well as new neighborhood. Algorithm converges when all nodes are happy. PS - I am looking for links for any mathematical analysis of the Schelling's model.

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  • Should not a tail-recursive function also be faster?

    - by Balint Erdi
    I have the following Clojure code to calculate a number with a certain "factorable" property. (what exactly the code does is secondary). (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (factor-9 (quot n 10)))))) Now, I'm into TCO and realize that Clojure can only provide tail-recursion if explicitly told so using the recur keyword. So I've rewritten the code to do that (replacing factor-9 with recur being the only difference): (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (recur (quot n 10)))))) To my knowledge, TCO has a double benefit. The first one is that it does not use the stack as heavily as a non tail-recursive call and thus does not blow it on larger recursions. The second, I think is that consequently it's faster since it can be converted to a loop. Now, I've made a very rough benchmark and have not seen any difference between the two implementations although. Am I wrong in my second assumption or does this have something to do with running on the JVM (which does not have automatic TCO) and recur using a trick to achieve it? Thank you.

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  • Drawing an honeycomb with as3

    - by vitto
    Hi, I'm trying to create an honeycomb with as3 but I have some problem on cells positioning. I've already created the cells (not with code) and for cycled them to a funcion and send to it the parameters which what I thought was need (the honeycomb cell is allready on a sprite container in the center of the stage). to see the structure of the cycle and which parameters passes, please see the example below, the only thing i calculate in placeCell is the angle which I should obtain directly inside tha called function Note: the angle is reversed but it isn't important, and the color are useful in example only for visually divide cases. My for cycle calls placeCell and passes cell, current_case, counter (index) and the honeycomb cell_lv (cell level). I thought it was what i needed but I'm not skilled in geometry and trigonometry, so I don't know how to position cells correctly: function placeCell (cell:Sprite, current_case:int, counter:int, cell_lv:int):void { var margin:int = 2; var angle:Number = (360 / (cell_lv * 6)) * (current_case + counter); var radius:Number = (cell.width + margin) * cell_lv; cell.x = radius * Math.cos (angle); cell.y = radius * Math.sin (angle); trace ("LV " + cell_lv + " current_case " + current_case + " counter " + counter + " angle " + angle + " radius " + radius) } how can I do to solve it?

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  • Using hashing to group similar records

    - by Neil Dobson
    I work for a fulfillment company and we have to pack and ship many orders from our warehouse to customers. To improve efficiency we would like to group identical orders and pack these in the most optimum way. By identical I mean having the same number of order lines containing the same SKUs and same order quantities. To achieve this I was thinking about hashing each order. We can then group by hash to quickly see which orders are the same. We are moving from an Access database to a PostgreSQL database and we have .NET based systems for data loading and general order processing systems, so we can either do the hashing during the data loading or hand this task over to the DB. My question firstly is should the hashing be managed by DB, possibly using triggers, or should the hash be created on-the-fly using a view or something? And secondly would it be best to calculate a hash for each order line and then to combine these to find an order-level hash for grouping, or should I just use a trigger for all CRUD operations on the order lines table which re-calculates a single hash for the entire order and store the value in the orders table? TIA

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  • Usage of Assert.Inconclusive

    - by Johannes Rudolph
    Hi, Im wondering how someone should use Assert.Inconclusive(). I'm using it if my Unit test would be about to fail for a reason other than what it is for. E.g. i have a method on a class that calculates the sum of an array of ints. On the same class there is also a method to calculate the average of the element. It is implemented by calling sum and dividing it by the length of the array. Writing a Unit test for Sum() is simple. However, when i write a test for Average() and Sum() fails, Average() is likely to fail also. The failure of Average is not explicit about the reason it failed, it failed for a reason other than what it should test for. That's why i would check if Sum() returns the correct result, otherwise i Assert.Inconclusive(). Is this to be considered good practice? What is Assert.Inconclusive intended for? Or should i rather solve the previous example by means of an Isolation Framework?

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