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  • Fastest way to list all primes below N in python

    - by jbochi
    This is the best algorithm I could come up with after struggling with a couple of Project Euler's questions. def get_primes(n): numbers = set(range(n, 1, -1)) primes = [] while numbers: p = numbers.pop() primes.append(p) numbers.difference_update(set(range(p*2, n+1, p))) return primes >>> timeit.Timer(stmt='get_primes.get_primes(1000000)', setup='import get_primes').timeit(1) 1.1499958793645562 Can it be made even faster? EDIT: This code has a flaw: Since numbers is an unordered set, there is no guarantee that numbers.pop() will remove the lowest number from the set. Nevertheless, it works (at least for me) for some input numbers: >>> sum(get_primes(2000000)) 142913828922L #That's the correct sum of all numbers below 2 million >>> 529 in get_primes(1000) False >>> 529 in get_primes(530) True EDIT: The rank so far (pure python, no external sources, all primes below 1 million): Sundaram's Sieve implementation by myself: 327ms Daniel's Sieve: 435ms Alex's recipe from Cookbok: 710ms EDIT: ~unutbu is leading the race.

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  • sorting using recursion

    - by user310587
    I have the following function to sort an array with even numbers in the front and odd numbers in the back. Is there a way to get it done without using any loops? //front is 0, back =array.length-1; arrangeArray (front, back); public static void arrangeArray (int front, int back) { if (front != back || front<back) { while (numbers [front]%2 == 0) front++; while (numbers[back]%2!=0) back--; if (front < back) { int oddnum = numbers [front]; numbers[front]= numbers[back]; numbers[back]=oddnum; arrangeArray (front+1, back-1); } } }

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  • Problem with echoing my array data in PHP

    - by ggfan
    I want to create an array of numbers: 10, 9,8...to 1. But when I echo $numbers, I get "Array" as the output as to the numbers. There is probably a simple thing I missed, can you please tell me. thanks! $numbers=array(); for ($i=10; $i>0; $i--){ array_push($numbers, $i); } echo $numbers;

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  • seeking to upgrade my bash magic. help decipher this command: bash -s stable

    - by tim
    ok so i'm working through a tutorial to get rvm installed on my mac. the bash command to get rvm via curl is curl -L https://get.rvm.io | bash -s stable i understand the first half's curl command at location rvm.io, and that the result is piped to the subsequent bash command, but i'm not sure what that command is doing. My questions: -s : im always confused about how to refer to these. what type of thing is this: a command line argument? a switch? something else? -s : what is it doing? i have googled for about half an hour but not sure how to refer to it makes it difficult. stable : what is this? tl;dr : help me decipher the command bash -s stable to those answering this post, i aspire to one day be as bash literate as you. until then, opstards such as myself thank you for the help!

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  • What is a Bias Value of Floating Point Numbers?

    - by mudge
    In learning how floating point numbers are represented in computers I have come across the term "bias value" that I do not quite understand. The bias value in floating point numbers has to do with the negative and positiveness of the exponent part of a floating point number. The bias value of a floating point number is 127 which means that 127 is always added to the exponent part of a floating point number. How does doing this help determine if the exponent is negative or positive or not?

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  • How do I allow users to dial numbers in my tableView cells?

    - by Griffo
    Hi all, I have a table containing cells with phone numbers. How can I allow the user to dial these numbers by tapping the row? It's not working by default and there's no option in interface builder like there is for uiwebviews so I imagine I need to programmatically tell the app to dial the number when the cell is tapped.

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  • Can an algorithmic process ever give true random numbers ?

    - by Arkapravo
    I have worked with random functions in python,ruby, MATLAB, Bash and Java. Nearly every programming language has a function to generate Random numbers. However, these apparently random sequences are termed as pseudo-random number sequences as the generation follows a deterministic approach, and the sequence seems to repeat (usually with a very large period). My question, can an algorithmic/programming process ever yield true random numbers ? The questions probably is more of theoretical computer science than just programming !

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  • How can I quickly sum all numbers in a file?

    - by Mark Roberts
    I have a file which contains several thousand numbers, each on it's own line: 34 42 11 6 2 99 ... I'm looking to write a script which will print the sum of all numbers in the file. I've got a solution, but it's not very efficient. (It takes several minutes to run.) I'm looking for a more efficient solution. Any suggestions?

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  • Prevent Negative numbers for Age without using client side validation.

    - by Deepak
    Hi People, I have an issue in Core java. Consider the Employee class having an attribute called age. class Employee{ private int age; public void setAge(int age); } My question is how do i restrict/prevent setAge(int age) method such that it accepts only positive numbers and it should not allow negative numbers, Note: This has to be done without using client side validation.how do i achieve it using Java/server side Validation only.The validation for age attribute should be handled such that no exception is thrown

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  • I'm trying to match some numbers in a string using a regexpressions and am having difficulty with th

    - by Ryan
    here is the line i'm trying to parse [\\?\Volume{d3f7f470-526b-11df-92eb-001a647802d2}\] 85 90 NotFound I'm basically just trying to get the numbers that are outside of the brackets and ignore anything in between the brackets. My original syntax worked until I realized that sometimes there would be numbers in the brackets (I was just using "([0-99]{2})") any help would be greatly appreciated. Thanks

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  • How can I enter only numbers in TextBox using JavaScript without disable right click ?

    - by Space Cracker
    I want to allow numbers only to be allowed for a textbox and I already do it onkeydown event by allow only numbers and prevent ctrl+V but I have two problems : if I make right click then paste so any char can be entered and I want a solution without disable right click by oncontextmenu="return false;" if I drag and drop any text it will be entered Is there any solution that can work in all browsers without problem ?

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  • PHP Magic faster than simply setting the class attribute?

    - by Marc Trudel
    Well, not exactly that, but here is an example. Can anyone explain the difference between B and C? How can it be faster to use a magic function to dynamically set a value instead of simply setting the value in the attribute definition? Here is some code: [root@vm-202-167-238-17 ~]# cat test.php; for d in A B C; do echo "------"; ./test.php $d; done; #!/usr/bin/php <?php $className = $argv[1]; class A { public function __get($a) { return 5; } } class B { public $a = 5; } class C { public function __get($a) { $this->a = 5; return 5; } } $a = new $className; $start = microtime(true); for ($i=0; $i < 1000000; $i++) $b = $a->a; $end = microtime(true); echo (($end - $start) * 1000) ." msec\n"; ------ 598.90794754028 msec ------ 205.48391342163 msec ------ 189.7759437561 msec

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  • Why isn't the pathspec magic :(exclude) excluding the files I specify from git log's output?

    - by Jubobs
    This is a follow-up to Ignore files in git log -p and is also related to Making 'git log' ignore changes for certain paths. I'm using Git 1.9.2. I'm trying to use the pathspec magic :(exclude) to specify that some patches should not be shown in the output of git log -p. However, patches that I want to exclude still show up in the output. Here is minimal working example that reproduces the situation: cd ~/Desktop mkdir test_exclude cd test_exclude git init mkdir testdir echo "my first cpp file" >testdir/test1.cpp echo "my first xml file" >testdir/test2.xml git add testdir/ git commit -m "added two test files" Now I want to show all patches in my history expect those corresponding to XML files in the testdir folder. Therefore, following VonC's answer, I run git log --patch -- . ":(exclude)testdir/*.xml" but the patch for my testdir/test2.xml file still shows up in the output: commit 37767da1ad4ad5a5c902dfa0c9b95351e8a3b0d9 Author: xxxxxxxxxxxxxxxxxxxxxxxxx Date: Mon Aug 18 12:23:56 2014 +0100 added two test files diff --git a/testdir/test1.cpp b/testdir/test1.cpp new file mode 100644 index 0000000..3a721aa --- /dev/null +++ b/testdir/test1.cpp @@ -0,0 +1 @@ +my first cpp file diff --git a/testdir/test2.xml b/testdir/test2.xml new file mode 100644 index 0000000..8b7ce86 --- /dev/null +++ b/testdir/test2.xml @@ -0,0 +1 @@ +my first xml file What am I doing wrong? What should I do to tell git log -p not to show the patch associated with all XML files in my testdir folder?

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  • Custom event loop and UIKit controls. What extra magic Apple's event loop does?

    - by tequilatango
    Does anyone know or have good links that explain what iPhone's event loop does under the hood? We are using a custom event loop in our OpenGL-based iPhone game framework. It calls our game rendering system, calls presentRenderbuffer and pumps events using CFRunLoopRunInMode. See the code below for details. It works well when we are not using UIKit controls (as a proof, try Facetap, our first released game). However, when using UIKit controls, everything almost works, but not quite. Specifically, scrolling of UIKit controls doesn't work properly. For example, let's consider following scenario. We show UIImagePickerController on top of our own view. UIImagePickerController covers our custom view We also pause our own rendering, but keep on using the custom event loop. As said, everything works, except scrolling. Picking photos works. Drilling down to photo albums works and transition animations are smooth. When trying to scroll photo album view, the view follows your finger. Problem: when scrolling, scrolling stops immediately after you lift your finger. Normally, it continues smoothly based on the speed of your movement, but not when we are using the custom event loop. It seems that iPhone's event loop is doing some magic related to UIKit scrolling that we haven't implemented ourselves. Now, we can get UIKit controls to work just fine and dandy together with our own system by using Apple's event loop and calling our own rendering via NSTimer callbacks. However, I'd still like to understand, what is possibly happening inside iPhone's event loop that is not implemented in our custom event loop. - (void)customEventLoop { OBJC_METHOD; float excess = 0.0f; while(isRunning) { animationInterval = 1.0f / openGLapp->ticks_per_second(); // Calculate the target time to be used in this run of loop float wait = max(0.0, animationInterval - excess); Systemtime target = Systemtime::now().after_seconds(wait); Scope("event loop"); NSAutoreleasePool* pool = [[ NSAutoreleasePool alloc] init]; // Call our own render system and present render buffer [self drawView]; // Pump system events [self handleSystemEvents:target]; [pool release]; excess = target.seconds_to_now(); } } - (void)drawView { OBJC_METHOD; // call our own custom rendering bool bind = openGLapp->app_render(); // bind the buffer to be THE renderbuffer and present its contents if (bind) { opengl::bind_renderbuffer(renderbuffer); [context presentRenderbuffer:GL_RENDERBUFFER_OES]; } } - (void) handleSystemEvents:(Systemtime)target { OBJC_METHOD; SInt32 reason = 0; double time_left = target.seconds_since_now(); if (time_left <= 0.0) { while((reason = CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, TRUE)) == kCFRunLoopRunHandledSource) {} } else { float dt = time_left; while((reason = CFRunLoopRunInMode(kCFRunLoopDefaultMode, dt, FALSE)) == kCFRunLoopRunHandledSource) { double time_left = target.seconds_since_now(); if (time_left <= 0.0) break; dt = (float) time_left; } } }

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  • NPE when drawing TabWidget in android (only on HTC Magic?)

    - by David Hedlund
    I've received report from the user of an app I've written that he gets FC whenever starting a certain activity. I have not been able to reproduce the issue on the emulator or on my HTC Hero (running 1.5), but this user running HTC Magic (with 1.6) is facing this error every time. What bothers me is that no single step in the stacktrace actually includes any code in my app (com.filmtipset) 01-07 00:10:26.773 I/ActivityManager( 141): Starting activity: Intent { cmp=com.filmtipset/.ViewMovie (has extras) } 01-07 00:10:27.023 D/AndroidRuntime( 2402): Shutting down VM 01-07 00:10:27.023 W/dalvikvm( 2402): threadid=3: thread exiting with uncaught exception (group=0x4001e170) 01-07 00:10:27.023 E/AndroidRuntime( 2402): Uncaught handler: thread main exiting due to uncaught exception 01-07 00:10:27.083 E/AndroidRuntime( 2402): java.lang.NullPointerException 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.TabWidget.dispatchDraw(TabWidget.java:173) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.View.draw(View.java:6552) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.FrameLayout.draw(FrameLayout.java:352) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.drawChild(ViewGroup.java:1531) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.View.draw(View.java:6552) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.widget.FrameLayout.draw(FrameLayout.java:352) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1883) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.draw(ViewRoot.java:1332) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.performTraversals(ViewRoot.java:1097) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.view.ViewRoot.handleMessage(ViewRoot.java:1613) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.os.Handler.dispatchMessage(Handler.java:99) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.os.Looper.loop(Looper.java:123) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at android.app.ActivityThread.main(ActivityThread.java:4320) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at java.lang.reflect.Method.invokeNative(Native Method) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at java.lang.reflect.Method.invoke(Method.java:521) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 01-07 00:10:27.083 E/AndroidRuntime( 2402): at dalvik.system.NativeStart.main(Native Method) Full dump here if I've missed anything of interest I'm guessing, then, that there might be something wrong with my layout. It's quite verbose, so I'm posting it here, rather than pasting the whole thing on SO. There is a tabwidget, where one tab is connected to the scrollview, svFilmInfo, and one to the linear layout llComments. The tab host is populated as such: Drawable commentSelector = getResources().getDrawable(R.drawable.tabcomment); Drawable infoSelector = getResources().getDrawable(R.drawable.tabinfo); mTabHost = getTabHost(); mTabHost.getTabWidget().setBackgroundColor(Color.BLACK); mTabHost.addTab(mTabHost.newTabSpec("tabInfo").setIndicator("Filminfo", infoSelector).setContent(R.id.svFilmInfo)); mTabHost.addTab(mTabHost.newTabSpec("tabInfo").setIndicator("Kommentarer", commentSelector).setContent(R.id.llComments)); Since I cannot reproduce the error myself, and since I cannot find any mention in the stack trace of what might be causing the error, I don't quite know where to start troubleshooting this. I'd appreciate any pointers.

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  • This program runs but not correctly; the numbers aren't right.

    - by user320950
    this program runs but not correctly numbers arent right, i read numbers from a file and then when i am using them in the program they are not right.:brief decription of what i am trying to do can someone tell me if something doesnt look right. this is what i have to do: write a program that determines the grade dispersal for 100 students You are to read the exam scores into three arrays, one array for each exam. You must then calculate how many students scored A’s (90 or above), B’s (80 or above), C’s (70 or above), D’s (60 or above), and F’s (less than 60). Do this for each exam and write the distribution to the screen. // basic file operations #include <iostream> #include <fstream> using namespace std; int read_file_in_array(double exam[100][3]); double calculate_total(double exam1[], double exam2[], double exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); double exam[100][3]; int main() { double go,go2,go3; double exam[100][3],exam1[100],exam2[100],exam3[100]; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; } /* int display_totals() { int grade_total; grade_total=calculate_total(exam1,exam2,exam3); return 0; } */ double calculate_total(double exam1[],double exam2[],double exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0; double exam[100][3]; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { for (j=0; j<3; j++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam[i][j] <=90 && exam[i][j] >=100) { above90++; { if(exam[i][j] <=80 && exam[i][j] >=89) { above80++; { if(exam[i][j] <=70 && exam[i][j] >=79) { above70++; { if(exam[i][j] <=60 && exam[i][j] >=69) { above60++; { if(exam[i][j] >=59) { fail++; } } } } } } } } } } } return 0; } int read_file_in_array(double exam[100][3]) { ifstream infile; int exam1[100]; int exam2[100]; int exam3[100]; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } int num, i=0,j=0; while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; { if (! (infile >> exam[i][j]) ) cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); } return 0; }

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  • Connect to VPN from Mac on Time Capsule network

    - by Lou Franco
    I have a few clients on my network that can connect to my work VPN (Windows PPTP) when they are not on my home network. On my home network (Cable Modem with Time Capsule providing Wifi), it fails very early -- looks like it can't even establish a connection. Logs just say that it failed -- even verbose logs don't have much: I redacted the host and IP from this log, but I can ping it. Wed Feb 2 14:32:41 2011 : PPTP connecting to server 'XXX.XXX.com' (XXX.XX.XX.XX)... Wed Feb 2 14:32:41 2011 : PPTP connection established. Wed Feb 2 14:32:41 2011 : using link 0 Wed Feb 2 14:32:41 2011 : Using interface ppp0 Wed Feb 2 14:32:41 2011 : Connect: ppp0 <--> socket[34:17] Wed Feb 2 14:32:41 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:32:44 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:32:47 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:32:50 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:32:53 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:32:56 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:32:59 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:33:02 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:33:05 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:33:08 2011 : sent [LCP ConfReq id=0x1 <asyncmap 0x0> <magic 0x543c7af8> <pcomp> <accomp>] Wed Feb 2 14:33:11 2011 : LCP: timeout sending Config-Requests Wed Feb 2 14:33:11 2011 : Connection terminated. Wed Feb 2 14:33:11 2011 : PPTP disconnecting... Wed Feb 2 14:33:11 2011 : PPTP disconnected Others can get to the VPN and I can too, but not on my network. The only clue I have seen in other forums is to set the NAT default host on the Time Capsule -- I set this to the IP that my mac got over DHCP. I made sure that my Mac gets a different range of IP addresses that it would get if it connected to the VPN (192.168.1.x vs. 10.0.0.x). Not using any VPN client -- just Network System Preferences. It has worked in the past -- but it was a while ago, so I can't pinpoint a change. My sysadmin doesn't even see incoming connections to the VPN (nothing logged about me when I connect). Looking for any diagnostic advice at all

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  • Python: How can I read in the characters from a line in a file and convert them to floats and strs, depending on if they are numbers or letters?

    - by user1467577
    I have a file that looks like: 1 1 C C 1.9873 2.347 3.88776 1 2 C Si 4.887 9.009 1.21 I would like to read in the contents of the file, line-by-line. When I only had numbers on the lines I used: for line in readlines(file): data = map(float, line.split) But this only works when all the elements of line.split are numbers. How can I make it store the letters as strings and the numbers as floats?

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