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  • simple sql group by custom groups question [migrated]

    - by alex
    imagine a mysql table that only has 2 columns, an id and a name of a color. with this query I know how many id's do I have for each color. SELECT color_name, count(id) FROM color_table GROUP BY (color_name); red:10 blue:5 yellow:3 green:1 my question is, is there a way I can specify to the "group by" some custom groups?? i mean, is there a query that results in this??: red:10 colors different than red: 9

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  • Question about design

    - by lukeluke
    Two fast questions about two design decisions: Suppose that you are checking collisions between game elements. When you find a collision between object 1 and object 2, do you play immediately a sound effect or do you insert it in a list and, in a later a stage, do you process all sound effects? Same question as above for user input. When the user presses key 'keypad left' do you insert the event in a queue and process it later or do you update character position immediately? Thx

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  • Install Script Question

    - by Michael Dobbins
    Sorry if this has been discussed, wasn't sure what to use to search for the particular question I had. I'm installing sickrage and couchpotato and headphones, and will be doing multiple installs I made a small batch script just to install everything but what I don't know how to do is automatically make them auto start on boot. Since they all require a file to be created I do not know how to make this file auto create and populate what needs to be put into it.

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  • Trying to calculate the 10001st prime number in Java.

    - by user247679
    Greetings. I am doing Problem 7 from Project Euler. What I am supposed to do is calculate the 10001st prime number. (A prime number being a number that is only divisible by itself and one.) Here is my current program: public class Problem7 { public static void main(String args []){ long numberOfPrimes = 0; long number = 2; while (numberOfPrimes < 10001){ if(isPrime(number)){ numberOfPrimes++; } number++; } System.out.println("10001st prime: "+ number); } public static boolean isPrime(long N) { if (N <= 1) return false; else return Prime(N,N-1); } public static boolean Prime(long X,long Y) { if (Y == 1) return true; else if (X % Y == 0) return false; else return Prime(X, Y-1); } } It works okay with finding, say the 100th prime number, but when I enter very large numbers such as 10001 it causes a stack overflow. Does anyone know of a way to fix this? Thanks for reading my problem!

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  • Project Euler (P14): recursion problems

    - by sean mcdaid
    Hi I'm doing the Collatz sequence problem in project Euler (problem 14). My code works with numbers below 100000 but with numbers bigger I get stack over-flow error. Is there a way I can re-factor the code to use tail recursion, or prevent the stack overflow. The code is below: import java.util.*; public class v4 { // use a HashMap to store computed number, and chain size static HashMap<Integer, Integer> hm = new HashMap<Integer, Integer>(); public static void main(String[] args) { hm.put(1, 1); final int CEILING_MAX=Integer.parseInt(args[0]); int len=1; int max_count=1; int max_seed=1; for(int i=2; i<CEILING_MAX; i++) { len = seqCount(i); if(len > max_count) { max_count = len; max_seed = i; } } System.out.println(max_seed+"\t"+max_count); } // find the size of the hailstone sequence for N public static int seqCount(int n) { if(hm.get(n) != null) { return hm.get(n); } if(n ==1) { return 1; } else { int length = 1 + seqCount(nextSeq(n)); hm.put(n, length); return length; } } // Find the next element in the sequence public static int nextSeq(int n) { if(n%2 == 0) { return n/2; } else { return n*3+1; } } }

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  • debugging scaffolding contingent upon degbugging boolean (java)

    - by David
    Recently i've found myself writing a lot of methods with what i can only think to call debugging scaffolding. Here's an example: public static void printArray (String[] array, boolean bug) { for (int i = 0; i<array.lenght; i++) { if (bug) System.out.print (i) ; //this line is what i'm calling the debugging scaffolding i guess. System.out.println(array[i]) ; } } in this method if i set bug to true, wherever its being called from maybe by some kind of user imput, then i get the special debugging text to let me know what index the string being printed as at just in case i needed to know for the sake of my debugging (pretend a state of affairs exists where its helpful). All of my questions more or less boil down to the question: is this a good idea? but with a tad bit more objectivity: Is this an effective way to test my methods and debug them? i mean effective in terms of efficiency and not messing up my code. Is it acceptable to leave the if (bug) stuff ; code in place after i've got my method up and working? (if a definition of "acceptability" is needed to make this question objective then use "is not a matter of programing controversy such as ommiting brackets in an if(boolean) with only one line after it, though if you've got something better go ahead and use your definition i won't mind) Is there a more effective way to accomplish the gole of making debugging easier than what i'm doing? Anything you know i mean to ask but that i have forgotten too (as much information as makes sense is appreciated).

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  • special debugging lines (java)

    - by David
    Recently i've found myself writing a lot of methods with what i can only think to call debugging scaffolding. Here's an example: public static void printArray (String[] array, boolean bug) { for (int i = 0; i<array.lenght; i++) { if (bug) System.out.print (i) ; //this line is what i'm calling the debugging scaffolding i guess. System.out.println(array[i]) ; } } in this method if i set bug to true, wherever its being called from maybe by some kind of user imput, then i get the special debugging text to let me know what index the string being printed as at just in case i needed to know for the sake of my debugging (pretend a state of affairs exists where its helpful). All of my questions more or less boil down to the question: is this a good idea? but with a tad bit more objectivity: Is this an effective way to test my methods and debug them? i mean effective in terms of efficiency and not messing up my code. Is it acceptable to leave the if (bug) stuff ; code in place after i've got my method up and working? (if a definition of "acceptability" is needed to make this question objective then use "is not a matter of programing controversy such as ommiting brackets in an if(boolean) with only one line after it, though if you've got something better go ahead and use your definition i won't mind) Is there a more effective way to accomplish the gole of making debugging easier than what i'm doing? Anything you know i mean to ask but that i have forgotten too (as much information as makes sense is appreciated).

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  • Using CSS max-height on an outer div to force scroll on an inner-div.

    - by Jay Neely
    I have an outer div with a variable height (and max-height) that's set with a specific pixel amount by JavaScript, containing two divs within. The 1st div is intended to hold a variable amount of content, e.g. a list of links. It has no height set. The 2nd div is intended to hold a fixed amount of content, and has a specific height set. Right now, the max-height isn't working. The 1st div keeps growing, even with overflow: auto; set, and pushes the 2nd div below it outside the bounds of the outer div. How can I make it so that when the 1st div gets too large for the outer div to contain both it and the fixed-height 2nd div, the 1st div will start to scroll? Example page: http://thevastdesign.com/scrollTest.html Thanks for any help. I'd appreciate a CSS solution the most, even if it requires some hacks. It only has to work in Firefox 3+, IE8, and IE7. Ideas?

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  • Differences between Assembly Code output of the same program

    - by ultrajohn
    I have been trying to replicate the buffer overflow example3 from this article aleph one I'm doing this as a practice for a project in a computer security course i'm taking so please, I badly need your help. I've been the following the example, performing the tasks as I go along. My problem is the assembly code dumped by gdb in my computer (i'm doing this on a debian linux image running on VM Ware) is different from that of the example in the article. There are some constructs which I find confusing. Here is the one from my computer: here is the one from the article... Dump of assembler code for function main: 0x8000490 <main>: pushl %ebp 0x8000491 <main+1>: movl %esp,%ebp 0x8000493 <main+3>: subl $0x4,%esp 0x8000496 <main+6>: movl $0x0,0xfffffffc(%ebp) 0x800049d <main+13>: pushl $0x3 0x800049f <main+15>: pushl $0x2 0x80004a1 <main+17>: pushl $0x1 0x80004a3 <main+19>: call 0x8000470 <function> 0x80004a8 <main+24>: addl $0xc,%esp 0x80004ab <main+27>: movl $0x1,0xfffffffc(%ebp) 0x80004b2 <main+34>: movl 0xfffffffc(%ebp),%eax 0x80004b5 <main+37>: pushl %eax 0x80004b6 <main+38>: pushl $0x80004f8 0x80004bb <main+43>: call 0x8000378 <printf> 0x80004c0 <main+48>: addl $0x8,%esp 0x80004c3 <main+51>: movl %ebp,%esp 0x80004c5 <main+53>: popl %ebp 0x80004c6 <main+54>: ret 0x80004c7 <main+55>: nop As you can see, there are differences between the two. I'm confuse and I can't understand totally the assembly code from my computer. I would like to know the differences between the two. How is pushl different from push, mov vs movl , and so on... what does the expression 0xhexavalue(%register) means? I am sorry If I'm asking a lot, But I badly need your help. Thanks for the help really...

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  • Delphi: How to avoid EIntOverflow underflow when subtracting?

    - by Ian Boyd
    Microsoft already says, in the documentation for GetTickCount, that you could never compare tick counts to check if an interval has passed. e.g.: Incorrect (pseudo-code): DWORD endTime = GetTickCount + 10000; //10 s from now ... if (GetTickCount > endTime) break; The above code is bad because it is suceptable to rollover of the tick counter. For example, assume that the clock is near the end of it's range: endTime = 0xfffffe00 + 10000 = 0x00002510; //9,488 decimal Then you perform your check: if (GetTickCount > endTime) Which is satisfied immediatly, since GetTickCount is larger than endTime: if (0xfffffe01 > 0x00002510) The solution Instead you should always subtract the two time intervals: DWORD startTime = GetTickCount; ... if (GetTickCount - startTime) > 10000 //if it's been 10 seconds break; Looking at the same math: if (GetTickCount - startTime) > 10000 if (0xfffffe01 - 0xfffffe00) > 10000 if (1 > 10000) Which is all well and good in C/C++, where the compiler behaves a certain way. But what about Delphi? But when i perform the same math in Delphi, with overflow checking on ({Q+}, {$OVERFLOWCHECKS ON}), the subtraction of the two tick counts generates an EIntOverflow exception when the TickCount rolls over: if (0x00000100 - 0xffffff00) > 10000 0x00000100 - 0xffffff00 = 0x00000200 What is the intended solution for this problem? Edit: i've tried to temporarily turn off OVERFLOWCHECKS: {$OVERFLOWCHECKS OFF}] delta = GetTickCount - startTime; {$OVERFLOWCHECKS ON} But the subtraction still throws an EIntOverflow exception. Is there a better solution, involving casts and larger intermediate variable types?

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  • Language for non-programmers to start learning programming

    - by zarawesome
    A non-programmer friend will be starting the Computer Science college course in a few months. I'd like her to try her hand at some programming before she starts her studies (the course itself expects one to know C, but it's an horrible language to learn to program at). What language would be the best to do so? Related question: Best ways to teach a beginner to program?

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  • Java Integer: what is faster comparison or subtraction?

    - by Vladimir
    I've found that java.lang.Integer implementation of compareTo method looks as follows: public int compareTo(Integer anotherInteger) { int thisVal = this.value; int anotherVal = anotherInteger.value; return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1)); } The question is why use comparison instead of subtraction: return thisVal - anotherVal;

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  • Scriptaculous Draggable/Droppable script not working properly when dragging into a scrolling div

    - by George
    I am using the Scriptaculous Draggable/Droppable scripts and have a problem when dragging into a scrolling div. I have the following layout (based on this question): #grid-container { left:33px; position:relative; width:300px; } #grid { width:310px; height:400px; overflow:auto; margin-bottom: 15px; } #grid-container ul { width:400px; list-style-type:none; white-space: nowrap; } #grid-container li { display:inline; list-style-type:none; padding:5px 15px 5px 15px; height:88px; text-align:center } .image-row { margin-left: 10px; } .grid-image { height:50px; margin-left:-20px; } Here is the html: <div id="grid-container"> <div id="grid"> <div id="row1" class="image-row"> <ul> <li><img id="img1" class="grid-image" src="images/img1.jpg"></li> <li><img id="img2" class="grid-image" src="images/img2.jpg"></li> <li><img id="img3" class="grid-image" src="images/img3.jpg"></li> <li><img id="img4" class="grid-image" src="images/img4.jpg"></li> </ul> </div> <div id="row2" class="image-row"> <ul> <li><img id="img5" class="grid-image" src="images/img5.jpg"></li> <li><img id="img6" class="grid-image" src="images/img6.jpg"></li> </ul> </div> </div> </div> I have another div with draggable items, while all of the img elements are droppable. This works very well for most cases, but when there are too many images for the grid and it has to scroll, I run into issues. I can still drag/drop into most items in that div, but when I scroll down and then try to drag onto an item in the bottom of the list, it drops on the row that was at the bottom before I scrolled the div. Even if I set the scroll attribute when creating the Draggable items, it will scroll the grid div, but not use the proper Droppable item. Is there any way to make the Draggable items drop onto the proper Droppable element regardless of if the containing div is scrolled or not?

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  • Is this implementation truely tail-recursive?

    - by CFP
    Hello everyone! I've come up with the following code to compute in a tail-recursive way the result of an expression such as 3 4 * 1 + cos 8 * (aka 8*cos(1+(3*4))) The code is in OCaml. I'm using a list refto emulate a stack. type token = Num of float | Fun of (float->float) | Op of (float->float->float);; let pop l = let top = (List.hd !l) in l := List.tl (!l); top;; let push x l = l := (x::!l);; let empty l = (l = []);; let pile = ref [];; let eval data = let stack = ref data in let rec _eval cont = match (pop stack) with | Num(n) -> cont n; | Fun(f) -> _eval (fun x -> cont (f x)); | Op(op) -> _eval (fun x -> cont (op x (_eval (fun y->y)))); in _eval (fun x->x) ;; eval [Fun(fun x -> x**2.); Op(fun x y -> x+.y); Num(1.); Num(3.)];; I've used continuations to ensure tail-recursion, but since my stack implements some sort of a tree, and therefore provides quite a bad interface to what should be handled as a disjoint union type, the call to my function to evaluate the left branch with an identity continuation somehow irks a little. Yet it's working perfectly, but I have the feeling than in calling the _eval (fun y->y) bit, there must be something wrong happening, since it doesn't seem that this call can replace the previous one in the stack structure... Am I misunderstanding something here? I mean, I understand that with only the first call to _eval there wouldn't be any problem optimizing the calls, but here it seems to me that evaluation the _eval (fun y->y) will require to be stacked up, and therefore will fill the stack, possibly leading to an overflow... Thanks!

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  • Raycasting "fisheye effect" question

    - by mattboy
    Continuing my exploration of raycasting, I am very confused about how the correction of the fisheye effect works. Looking at the screenshot below from the tutorial at permadi.com, the way I understand the cause of the fisheye effect is that the rays that are cast are distances from the player, rather than the distances perpendicular to the screen (or camera plane) which is what really needs to be displayed. The distance perpendicular to the screen then, in my world, should simply be the distance of Y coordinates (Py - Dy) assuming that the player is facing straight upwards. Continuing the tutorial, this is exactly how it seems to be according to the below screenshot. From my point of view, the "distorted distance" below is the same as the distance PD calculated above, and what's labelled the "correct distance" below should be the same as Py - Dy. Yet, this clearly isn't the case according to the tutorial. My question is, WHY is this not the same? How could it not be? What am I understanding and visualizing wrong here?

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  • Music Rhythm Game: Copyright Music Question for Independent (Indie) Game Developers

    - by David Dimalanta
    I have a curious question regarding on musics used in music rhythm game. In Guitar Hero for example, they used all different music albums in one program. Then, each album requires to ask permission to the owner, composer of the music, or the copyright owner of the music. Let's say, if you used 15 albums for the music rhythm game, then you have to contact 15 copyright owners and it might be that, for the game developer, that the profit earned goes to the copyright owner or owner of this music. For the independent game developers, was it okay if either used the copyright music by just mentioning the name of the singer included in the credits and in the music select screen or use the non-popular/old music that about 50 years ago? And, does still earn money for the indie game developers by making free downloadable game?

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  • Legal question.

    - by Kjow
    Hi all, a question bounces in my head from some time. Copyright laws are different by nation to nation, but generally which is the border line to break a copyright? Suppose to make a game that is very similar to an other come out in the past, e.g. a Pacman clone or a Space Invaders clone, but nothing from original titles are grabbed and maybe they're not made in 2d, but in 3d. The titles aren't "Pacman clone - the return" or "Space Invaders - they did it again", and not also "Pocman" or "Space Evaders" (maybe this last could be fun for some "creative financers" that need to escape from earth :D). Finally suppose to call these some thing like "Popcorn, fruit and ghosts" (or the acronym: "PFG") and "Kill all enemy" (or the acronym: "KAE"). In this case (not grab- all self-made) and no references to original titles, but with a game that feels very similar to "ispiration ones"... they could be sold to somewhere like "Valve's Steam"? Regards, Kjow

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  • TDD - A question about the approach

    - by k25
    I have a question about TDD. I have always seen the recommendation that we should first write unit tests and then start writing code. But I feel that going the other way is much more comfortable (for me) - write code and then the unit tests, because I feel we have much more clarity after we have written the actual code. If I write the code and then the tests, I may have to change my code a little bit to make it testable, even if I concentrate much on creating a testable design. On the other hand, if I write the tests and then the code, the tests will change pretty frequently as and when the code shapes up. My questions are: 1) As I see a lot of recommendations to start writing tests and then move on to coding, what are the disadvantages if I do it the other way - write code and then the unit tests? 2) Could you please point me to some links that discuss about this or recommend some books (TDD)?

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  • Item 2, Scott Myers Effective C++ question

    - by user619818
    In Item2 on page 16, (Prefer consts, enums, and inlines to #defines), Scott says: 'Also, though good compilers won't set aside storage for const objects of integer types'. I don't understand this. If I define a const object, eg const int myval = 5; then surely the compiler must set aside some memory (of int size) to store the value 5? Or is const data stored in some special way? This is more a question of computer storage I suppose. Basically, how does the computer store const objects so that no storage is set aside?

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  • Raycasting tutorial / vector math question

    - by mattboy
    I'm checking out this nice raycasting tutorial at http://lodev.org/cgtutor/raycasting.html and have a probably very simple math question. In the DDA algorithm I'm having trouble understanding the calcuation of the deltaDistX and deltaDistY variables, which are the distances that the ray has to travel from 1 x-side to the next x-side, or from 1 y-side to the next y-side, in the square grid that makes up the world map (see below screenshot). In the tutorial they are calculated as follows, but without much explanation: //length of ray from one x or y-side to next x or y-side double deltaDistX = sqrt(1 + (rayDirY * rayDirY) / (rayDirX * rayDirX)); double deltaDistY = sqrt(1 + (rayDirX * rayDirX) / (rayDirY * rayDirY)); rayDirY and rayDirX are the direction of a ray that has been cast. How do you get these formulas? It looks like pythagorean theorem is part of it, but somehow there's division involved here. Can anyone clue me in as to what mathematical knowledge I'm missing here, or "prove" the formula by showing how it's derived?

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  • Question on refactoring and code design

    - by Software Engeneering Learner
    Suppose, I have a class with a constant static final field. Then I want in certain situations that field to be different. It still can be final, because it should be initialized in constructor. My question is, what strategy I should use: add this field value into the constructor create 2 subclasses, replace original field usage with some protected method and override it in subclasses Or create some composite class that will held instance of my class inside and somehow change that value? Which approach should I use and why?

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  • C# XNA - Sky Sphere Question

    - by Wade
    I have been banging my head against the wall trying to get a sky sphere to work appropriately in XNA 4.0. I have the sphere loading correctly, and even textured, but i would like something a little more dynamic that can support a day/night cycle. My issue is that, while i know a good amount of C# and XNA, i know next to nothing about HLSL. (I could make an ambient light shader if my life depended on it...) I also have not been able to find a tutorial on how to build a sky sphere like this. Of course i don't expect to be able to make an amazing one right off the bat, i would like to start small, with a dynamic coloring sky i'll work out the clouds and sun later. My first question: Does anyone know of any good tutorial sites that could help me get a decent grasp around HLSL? Second: Does anyone have a good example of or know where to find one of a gradient sky using XNA and C#?

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  • SDL to SFML simple question

    - by ultifinitus
    Hey! I've been working on a game in c++ for about a week and a half, and I've been using SDL. However, my current engine only needs the following from whatever library I use: enable double buffering load an image from path into something that I can apply to the screen apply an image to the screen with a certain x,y enable transparency on an image (possibly) image clipping, for sprite sheets. I am fairly sure that SFML has all of this functionality, I'm just not positive. Will someone confirm my suspicions? Also I have one or two questions regarding SFML itself. Do I have to do anything to enable hardware accelerated rendering? How quick is SFML at blending alpha values? (sorry for the less than intelligent question!)

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