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  • Floating point arithmetic is too reliable.

    - by mcoolbeth
    I understand that floating point arithmetic as performed in modern computer systems is not always consistent with real arithmetic. I am trying to contrive a small C# program to demonstrate this. eg: static void Main(string[] args) { double x = 0, y = 0; x += 20013.8; x += 20012.7; y += 10016.4; y += 30010.1; Console.WriteLine("Result: "+ x + " " + y + " " + (x==y)); Console.Write("Press any key to continue . . . "); Console.ReadKey(true); } However, in this case, x and y are equal in the end. Is it possible for me to demonstrate the inconsistency of floating point arithmetic using a program of similar complexity, and without using any really crazy numbers? I would like, if possible, to avoid mathematically correct values that go more than a few places beyond the decimal point.

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  • Junit vs TestNG

    - by Sam Merrell
    At work we are currently still using Junit3 to run our tests. We have been considering switching over to Junit4 for new tests being written but I have been keeping an eye on TestNG for a while now. What experiences have you all had with either Junit4 or TestNG and which seems to work better for very large numbers of tests. Having flexibility in writing tests is also important to us since our functional tests cover a wide aspect and need to be written in a variety of ways to get results. Old tests will not be re-written as they do their job just fine. What I would like to see in new tests though is flexibility in the way the test can be written, natural assertions, grouping, and easily distributed test executions.

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  • PHP: Alternative to SESSIONS

    - by iamjonesy
    Hi, I have a PHP application that relies on session variables quite a lot. After login the user get redirected to a page that executes code to set up a load of session variables depending on who the user is. The application is using data from different sources and the sessions are used to store ID numbers to query the databases. So when the user goes to a page that will query their asset management system their ID for that particular database is called via the session. I've had a LOT of problems with session variables recently. Sometimes only one session file is created during the lifetime of the app, and sometimes each session request results in a new session id (still haven't managed to find out why!). My question is this. Is there an alternative to using session variables for this? Like globals or some other way? Any help most appreciated! Regards, Jonesy

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  • possible to make text messaging with php have a constant "telephone number" value?

    - by Rees
    hello, i have an iphone 3g and can successfully send text messages using the PHP mail() function. My issue is that for each message i receive, the "telephone number" associated with the incoming text message changes each time. If possible, I would like to somehow make this number constant so that I can take advantage of iphone's ability to aggregate all text messages from the same telephone number -Otherwise my iphone would be cluttered with messages. Is there a way to do this? an example of the numbers I receive would be 1(410) 000-001, 1(410) 000-002, 1(410) 000-003, etc... can i make this constant somehow? $message = stripslashes("new user just joined!"); mail("[email protected]", "Subject", "$message"); please let me know! thanks...

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  • Why unsigned int contained negative number

    - by Daziplqa
    Hi All, I am new to C, What I know about unsigned numerics (unsigned short, int and longs), that It contains positive numbers only, but the following simple program successfully assigned a negative number to an unsigned int: 1 /* 2 * ===================================================================================== 3 * 4 * Filename: prog4.c 5 * 6 * ===================================================================================== 7 */ 8 9 #include <stdio.h> 10 11 int main(void){ 12 13 int v1 =0, v2=0; 14 unsigned int sum; 15 16 v1 = 10; 17 v2 = 20; 18 19 sum = v1 - v2; 20 21 printf("The subtraction of %i from %i is %i \n" , v1, v2, sum); 22 23 return 0; 24 } The output is : The subtraction of 10 from 20 is -10

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  • Masked Edit Extender Format Issue

    - by Kumar
    I am using an ASP.NET AJAX Masked Edit Extender to format phone numbers <asp:TextBox ID="tbPhoneNumber" runat="server" /> <ajaxToolkit:MaskedEditExtender TargetControlID="tbPhoneNumber" Mask="(999)999-9999" MaskType="Number" InputDirection="LeftToRight" ClearMaskOnLostFocus="false" ClearTextOnInvalid="false" runat="server" AutoComplete="false" /> On the page load event I am trying to populate the phone textbox as follows: protected void Page_Load(object sender, EventArgs e) { tbPhoneNumber.Text = "(394)456-310"; } So there is one number which is missing at the end to make it a valid phone number. When the page loads I expected the value in the textbox to be (394)456-310_ But it displays (_39)445-6310 Why is this happening?

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  • Add a thousands separator to a total with Javascript or jQuery?

    - by Matt
    I have a function that sums a column of data in an html table. It does so admirably only I would like to have it put the commas in there that are needed to separate the thousands. Initially, you'll note, there are commas in the numbers being added. So that the function will add them, they are removed. How do I add the commas back in there? <script type="text/javascript"> function sumOfColumns(tableID, columnIndex, hasHeader) { var tot = 0; $("#" + tableID + " tr" + (hasHeader ? ":gt(0)" : "")) .children("td:nth-child(" + columnIndex + ")") .each(function() { tot += parseInt($(this).html().replace(',', '')); }); return "Total Pounds Entered : " + tot; } </script>

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  • Calculating a range of an exact number of values in Python

    - by Einar
    Hello, I'm building a range between two numbers (floats) and I'd like this range to be of an exact fixed length (no more, no less). range and arange work with steps, instead. To put things into pseudo Python, this is what I'd like to achieve: start_value = -7.5 end_value = 0.1 my_range = my_range_function(star_value, end_value, length=6) print my_range [-7.50,-5.98,-4.46,-2.94,-1.42,0.10] This is essentially equivalent to the R function seq which can specify a sequence of a given length. Is this possible in Python? Thanks.

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  • Math algorithm question

    - by Senica Gonzalez
    I'm not sure if this can be done without some determining factor....but wanted to see if someone knew of a way to do this. I want to create a shifting scale for numbers. Let's say I have the number 26000. I want the outcome of this algorithm to be 6500; or 25% of the original number. But if I have the number 5000, I want the outcome to be 2500; or 50% of the original number. The percentages don't have to be exact, this is just an example. I just want to have like a sine wave sort of thing. As the input number gets higher, the output number is a lower percentage of the input. Does that make sense?

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  • High density Silverlight charting control

    - by ahosie
    I've been looking into Silverlight charting controls to display a large number of samples, (~10,000 data points in five separate series - ~50k points all up). I have found the existing options produced by Dundas, Visifire, Microsoft etc to be extremely poor performers when displaying more than a few hundred data points. I believe the performance issues with existing chart controls is caused by the heavy use of vector graphics. Ergo one solution would be a client-side chart control that uses the WritableBitmap class to generate a raster chart. Before I fall too far down the wheel re-invention rabbit hole - has anyone found a third party or OSS control that will manage large numbers of data points on a sparkline?

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  • What can I access in Androids Native libraries? And How?

    - by Donal Rafferty
    I am completely new to the NDK. I have done a couple of the tutorials including the hello from jni one and another one that calculates the sum of two numbers. They involved using cygwin and the ndk to create the library so file and I have a bit of a grasp on how to insert my own libraries into the libraries layer of Android. I have now been asked to access the native libraries on Android and see what I can use them for. My question is can I do this? The STABLE-APIS.txt document is a bit vague and mentions the following as Stable C++ API's in Android 1.5 cstddef new utility stl_pair.h Does that mean I can access them? If so then how do I go about it? I dont think that following the tutorials I have already done would be any help? Any pointers on how to do this or links to tutorials etc.. would be greatly appreciated

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  • How do I make "simple" throughput servlet-filter?

    - by Tommy
    I'm looking to create a filter that can give me two things: number of request pr minute, and average responsetime pr minute. I already got the individual readings, I'm just not sure how to add them up. My filter captures every request, and it records the time each request takes: public void doFilter(ServletRequest request, ...() { long start = System.currentTimeMillis(); chain.doFilter(request, response); long stop = System.currentTimeMillis(); String time = Util.getTimeDifferenceInSec(start, stop); } This information will be used to create some pretty Google Chart charts. I don't want to store the data in any database. Just a way to get current numbers out when requested As this is a high volume application; low overhead is essential. I'm assuming my applicationserver doesn't provide this information.

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  • Next month, same day in PHP

    - by Guillermo
    I got a last time (and urgent) requeriment of an "event" that needs to be scheduled the same day of every month. Say of you set the start date on the 1st May you should get the next events on the 1st of Jun, 1 Jul etc. The problem comes with a start date on the 31st (the next ones could be 30 or 28 depending on the month) Considering that there are months with different numbers of days (28,30,31) depending on the month itself and the year... what would ba an easy way to setup this? Consider the following (and flawed) nextmonth function: $events = array() function nextmonth($date) { return $date+(60*60*24*30); } $curr = $start; while($curr < $end) { $events[ = $curr; $curr = nextmonth($curr); } Edited to add: The problem for me is, simply enought, is to solve what the number of days of any given month is and thus get the next corresponding date..

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  • computing z-scores for 2D matrices in scipy/numpy in Python

    - by user248237
    How can I compute the z-score for matrices in Python? Suppose I have the array: a = array([[ 1, 2, 3], [ 30, 35, 36], [2000, 6000, 8000]]) and I want to compute the z-score for each row. The solution I came up with is: array([zs(item) for item in a]) where zs is in scipy.stats.stats. Is there a better built-in vectorized way to do this? Also, is it always good to z-score numbers before using hierarchical clustering with euclidean or seuclidean distance? Can anyone discuss the relative advantages/disadvantages? thanks.

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  • Navigate touch-tone menus via modem

    - by Kongress
    I have a system that I need to programmatically interface with that requires a set of numbers to be dialed after the phone line is picked up, like a standard automated phone answering system. For instance, dial the number 123-456-7890, wait for the line to be answered, wait 15 seconds for the voice prompt, dial 1234#, hang up. The question is, can I and how do I do that through a modem? I know how to dial a number through a modem, it's simply ATDT[phone number], but that will attempt to initiate a data connection which will not allow touch-tone number entry. Would a voice modem provide the necessary capability? If so, could anyone provide example commands to accomplish this?

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  • Recording/Reading C doubles in the IEEE 754 interchange format

    - by rampion
    So I'm serializing a C data structure for cross-platform use, and I want to make sure I'm recording my floating point numbers in a cross-platform manner. I had been planning on just doing char * pos; /*...*/ *((double*) pos) = dataStructureInstance->fieldWithOfTypeDouble; pos += sizeof(double); But I wasn't sure that the bytes would be recorded in the char * array in the IEEE 754 interchange format. I've been bitten by cross-platform issues before (endian-ness and whatnot). Is there anything I need to do to a double to get the bytes in interchange format?

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  • C# CultureInfo NumberFormat NumberDecimalSeparator Problem

    - by Mahdi
    I want to change NumberDecimalSeparator of my application from "." to "/". it works when i show float numbers in my textbox. but integer types are not shown at all. I modify thread's culture to get application-wide formatting. my code is like this: CultureInfo ci = new CultureInfo("fa-IR", true); ci.NumberFormat.DigitSubstitution = DigitShapes.NativeNational; ci.NumberFormat.NumberDecimalSeparator = "/"; Thread.CurrentThread.CurrentCulture = ci; result: 3.14 = "3/14" 100 = "" Any help please ?

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  • Why are primes important in cryptography?

    - by Michael Stum
    One thing that always strikes me as a non-cryptographer: Why is it so important to use Prime numbers? What makes them so special in cryptography? Does anyone have a simple short explanation? (I am aware that there are many primers and that Applied Cryptography is the Bible, but as said: I am not looking to implement my own cryptographic algorithm, and the stuff that I found just made my brain explode - no 10 pages of math formulas please :)) Thanks for all the answers. I've accepted the one that made the actual concept most clear to me.

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  • convert string to float without silent NaN/Inf conversion

    - by Peter Hansen
    I'd like convert strings to floats using Python 2.6 and later, but without silently converting things like 'NaN' and 'Inf'. Before 2.6, float("NaN") would raise a ValueError. Now it returns a float for which math.isnan() returns True, which is not useful behaviour for my application. Here's what I've got at the moment: import math def get_floats(source): for text in source.split(): try: val = float(text) if math.isnan(val) or math.isinf(val): raise ValueError yield val except ValueError: pass This is a generator, which I can supply with strings containing whitespace-separated sequences representing real numbers. I'd like it to yield only those fields which are purely numeric representations of floats, as in "1.23" or "-34e6", but not for example "NaN" or "-Inf". Test case: assert list(get_floats('1.23 -34e6 NaN -Inf')) == [1.23, -34000000.0] Please suggest alternatives you consider more elegant, even if they involve "look before you leap" (which is normally considered a lesser approach in Python).

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  • How to set an array to a list of values in VB.NET?

    - by IPX Ares
    I cannot figure out how to set an array to one of two sets of numbers (there will be more later), every way that I have tried throws some kind of error. I have tried to Dim the array inside the case statements, but then I cannot use the array in the For Each, which makes this worthless.... any ideas would be appreciated. Code: Dim HourArray() As Integer Select Case CurrentShapeRow(ROW_PERIOD) Case "ON", "2X16" HourArray = {6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21} Case "2X8", "5X8" HourArray = {0, 1, 2, 3, 4, 5, 22, 23} Case Else Throw New Exception(String.Format("Unhandled Period: {0}", CurrentShapeRow(ROW_PERIOD))) End Select For Each HourCount As Integer In HourArray() 'DO SOME STUFF HERE Next

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  • How do I use Python's itertools.groupby()?

    - by James Sulak
    I haven't been able to find an understandable explanation of how to actually use Python's itertools.groupby() function. What I'm trying to do is this: take a list - in this case, the children of an objectified lxml element - divide it into groups based on some criteria, and then later iterate over each of these groups separately. I've reviewed the documentation (http://docs.python.org/lib/itertools-functions.html), and the examples, (http://docs.python.org/lib/itertools-example.html), but I've had trouble trying to apply them beyond a simple list of numbers. So, how do I use of itertools.groupby()? Is there another technique I should be using? Pointers to good "prerequisite" reading would also be appreciated.

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  • fast algorithm implementation to sort very small set

    - by aaa
    hello. This is the problem I ran into long time ago. I thought I may ask your for your ideas. assume I have very small set of numbers (integers), 4 or 8 elements, that need to be sorted, fast. what would be the best approach/algorithm? my approach was to use the max/min functions. I guess my question pertains more to implementation, rather than type of algorithm. At this point it becomes somewhat hardware dependent , so let us assume Intel 64-bit processor with SSE3 . Thanks

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  • Replicate UISegmentedControl with UIButtons - iPhone

    - by Sam
    Hi guys, I didnt like the style of UISegmentedControl, hence i tried to change the way it looked, but I couldnt attach images to its buttons. I just didnt change at all. Now i'm looking at how to replicate that function with 4 UIButtons. I've setup 4 UIButtons in interface builder, added different tag numbers to them. What i cannot accomplish is when a button is tapped, it should be "selected" and the other buttons should be Unselected. How can i connect all of them? And if there was a way to change the UISegmented control looks, i would need all this effort. thanks for the help guys this is for iPhone OS

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  • Word 2007 Question

    - by Lijo
    Hi Team, While preparing a Word 2007 document, I made a mistake. (Not to say I don't have any other copy of the document) While formatting (as a try) I applied the style "Apply Style to Body to match selection". This caused the document to go totally in a wronfg format - having numbers even in tables. Have you ever faced this? Could you please tell how to correct it? Hope you would be kind enough to answer this even though it is not striclty technical. Thanks Lijo

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  • Call methods in main method

    - by Niloo
    this is my main method that gets 3 integers from command line and I parse then in my validating method. However I have one operation method that calls 3 other methods, but i don't know what type of data and howmany I have to put in my operatinMethod() " cuase switch only gets one); AND also in my mainMethod() for calling the operationMehod(); itself? please let me know if i'm not clear? Thanx! main method: public class test { // Global Constants final static int MIN_NUMBER = 1; final static int MAX_PRIME = 10000; final static int MAX_FACTORIAL = 12; final static int MAX_LEAPYEAR = 4000; //Global Variables static int a,b,c; public static void main (String[] args) { for(int i =0; i< args.length; i++){} if(validateInput(args[0],args[1],args[2])){ performOperations(); } } //Validate User Input public static boolean validateInput(String num1,String num2,String num3){ boolean isValid = false; try{ try{ try{ a = Integer.parseInt(num1); if(!withinRange(a,MIN_NUMBER, MAX_PRIME)) { System.out.println("The entered value " + num1 +" is out of range [1 TO 10000]."); } isValid = true; } catch(Exception ex) { System.out.println("The entered value " + num1 + " is not a valid integer. Please try again."); } b = Integer.parseInt(num2); if(!withinRange(b,MIN_NUMBER, MAX_FACTORIAL)) { System.out.println("The entered value " + num2 +" is out of range [1 TO 12]."); } isValid = true; } catch(Exception ex) { System.out.println("The entered value " + num2 + " is not a valid integer. Please try again."); } c = Integer.parseInt(num3); if(!withinRange(c,MIN_NUMBER, MAX_LEAPYEAR)) { System.out.println("The entered value " + num3 +" is out of range [1 TO 4000]."); } isValid = true; } catch(Exception ex) { System.out.println("The entered value " + num3 + " is not a valid integer. Please try again."); } return isValid; } //Check the value within the specified range private static boolean withinRange(int userInput ,int min, int max){ boolean isInRange = true; if(userInput < min || userInput > max){ isInRange = false; } return isInRange; } //Perform operations private static void performOperations(int userInput) { switch(userInput) { case 1: // count Prime numbers countPrimes(a); break; case 2: // Calculate factorial getFactorial(b); break; case 3: // find Leap year isLeapYear(c); break; } } // Verify Prime Number private static boolean isPrime(int prime) { for(int i = 2; i <= Math.sqrt(prime) ; i++) { if ((prime % i) == 0) { return false; } } return true; } // Calculate Prime private static int countPrimes(int userInput){ int count =0; for(int i=userInput; i<=MAX_PRIME; i++) { if(isPrime(i)){ count++; } } System.out.println("Exactly "+ count + " prime numbers exist between "+ a + " and 10,000."); return count; } // Calculate the factorial value private static int getFactorial(int userInput){ int ans = userInput; if(userInput >1 ){ ans*= (getFactorial(userInput-1)); //System.out.println("The value of "+ b +"! is "+ getFactorial(userInput)); } return ans; } // Determine whether the integer represents a leap year private static boolean isLeapYear(int userInput){ if (userInput % 4 == 0 && userInput % 400 == 0 && userInput % 100 ==0){ System.out.println("The year "+ c +" is a leap year"); } else { System.out.println("The year "+ c +" is a not leap year"); } return false; } }

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