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  • why there is no power operator in java / c ++?

    - by RanZilber
    While there is such operator - ** in Python , i was wondering why java and c++ havent got one too. It is easy to make one for classes you define in C++ with operator overloading ( and i believe such thing is possible also in java) , but when talking about primitive types such as int, double and so on , you'll have to use library function like Math.power (and usaully have to cast both to double). So - why not define such operator for primitive types ?

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  • How can I deal with the cargo-cult programming attitude?

    - by Aivar
    I have some computer science students in a compulsory introductory programming course who see programming language as a set of magic spells, which must be cast in order to achieve some effect (instead of seeing it as a flexible medium for expressing their idea of solution). They tend to copy-paste code from previous, similar-looking assignments without considering the essence of the problem. Can anyone recommend some exercises or analogies to make these students more confident that they can, and should, understand the structure and meaning of each piece of code they write?

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  • Why Your Abstract Wasn't Selected

    - by AllenMWhite
    We're anxiously waiting to hear from PASS which sessions were selected for the 2014 Summit in November. It's a big job to go through the hundreds of submissions and pick the sessions that will appeal to the people who will be paying over $1,000 to attend this annual event. As I am also waiting to hear the results, I saw this article addressed to actors who didn't get cast for the part they worked so hard to audition for, and it seemed appropriate to address the same issues for would-be Summit speakers....(read more)

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  • C++ strongly typed typedef

    - by Kian
    I've been trying to think of a way of declaring strongly typed typedefs, to catch a certain class of bugs in the compilation stage. It's often the case that I'll typedef an int into several types of ids, or a vector to position or velocity: typedef int EntityID; typedef int ModelID; typedef Vector3 Position; typedef Vector3 Velocity; This can make the intent of code more clear, but after a long night of coding one might make silly mistakes like comparing different kinds of ids, or adding a position to a velocity perhaps. EntityID eID; ModelID mID; if ( eID == mID ) // <- Compiler sees nothing wrong { /*bug*/ } Position p; Velocity v; Position newP = p + v; // bug, meant p + v*s but compiler sees nothing wrong Unfortunately, suggestions I've found for strongly typed typedefs include using boost, which at least for me isn't a possibility (I do have c++11 at least). So after a bit of thinking, I came upon this idea, and wanted to run it by someone. First, you declare the base type as a template. The template parameter isn't used for anything in the definition, however: template < typename T > class IDType { unsigned int m_id; public: IDType( unsigned int const& i_id ): m_id {i_id} {}; friend bool operator==<T>( IDType<T> const& i_lhs, IDType<T> const& i_rhs ); }; Friend functions actually need to be forward declared before the class definition, which requires a forward declaration of the template class. We then define all the members for the base type, just remembering that it's a template class. Finally, when we want to use it, we typedef it as: class EntityT; typedef IDType<EntityT> EntityID; class ModelT; typedef IDType<ModelT> ModelID; The types are now entirely separate. Functions that take an EntityID will throw a compiler error if you try to feed them a ModelID instead, for example. Aside from having to declare the base types as templates, with the issues that entails, it's also fairly compact. I was hoping anyone had comments or critiques about this idea? One issue that came to mind while writing this, in the case of positions and velocities for example, would be that I can't convert between types as freely as before. Where before multiplying a vector by a scalar would give another vector, so I could do: typedef float Time; typedef Vector3 Position; typedef Vector3 Velocity; Time t = 1.0f; Position p = { 0.0f }; Velocity v = { 1.0f, 0.0f, 0.0f }; Position newP = p + v*t; With my strongly typed typedef I'd have to tell the compiler that multypling a Velocity by a Time results in a Position. class TimeT; typedef Float<TimeT> Time; class PositionT; typedef Vector3<PositionT> Position; class VelocityT; typedef Vector3<VelocityT> Velocity; Time t = 1.0f; Position p = { 0.0f }; Velocity v = { 1.0f, 0.0f, 0.0f }; Position newP = p + v*t; // Compiler error To solve this, I think I'd have to specialize every conversion explicitly, which can be kind of a bother. On the other hand, this limitation can help prevent other kinds of errors (say, multiplying a Velocity by a Distance, perhaps, which wouldn't make sense in this domain). So I'm torn, and wondering if people have any opinions on my original issue, or my approach to solving it.

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  • SEO Techniques - How to Get Quality Backlinks Fast

    Backlinks are like votes for you in a page rank election, you are the candidate and the votes are your backlinks. The more votes you receive and the more important the people who cast those votes for you then the better popularity you have and that is how Google looks at it as well.

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  • Why Your Abstract Wasn't Selected

    - by AllenMWhite
    We're anxiously waiting to hear from PASS which sessions were selected for the 2014 Summit in November. It's a big job to go through the hundreds of submissions and pick the sessions that will appeal to the people who will be paying over $1,000 to attend this annual event. As I am also waiting to hear the results, I saw this article addressed to actors who didn't get cast for the part they worked so hard to audition for, and it seemed appropriate to address the same issues for would-be Summit speakers....(read more)

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  • Java exception when the traffic grow up

    - by sahid
    I have an error with java/solr when the traffic grows up. It seems Solr tries to cast a java.lang.Object to a org.apache.solr.common.util.ConcurrentLRUCache$CacheEntry SEVERE: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Lorg.apache.solr.common.util.ConcurrentLRUCache$CacheEntry; at org.apache.solr.common.util.ConcurrentLRUCache$PQueue.myInsertWithOverflow(ConcurrentLRUCache.java:377) at org.apache.solr.common.util.ConcurrentLRUCache.markAndSweep(ConcurrentLRUCache.java:329) at org.apache.solr.common.util.ConcurrentLRUCache.put(ConcurrentLRUCache.java:144) at org.apache.solr.search.FastLRUCache.put(FastLRUCache.java:131) at org.apache.solr.search.SolrIndexSearcher.getDocSet(SolrIndexSearcher.java:573) at org.apache.solr.search.SolrIndexSearcher.getDocSet(SolrIndexSearcher.java:641) at org.apache.solr.search.SolrIndexSearcher.getDocListNC(SolrIndexSearcher.java:1109) at org.apache.solr.search.SolrIndexSearcher.getDocListC(SolrIndexSearcher.java:1090) at org.apache.solr.search.SolrIndexSearcher.search(SolrIndexSearcher.java:337) at org.apache.solr.handler.component.QueryComponent.process(QueryComponent.java:431) at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:231) at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:129) at org.apache.solr.core.SolrCore.execute(SolrCore.java:1298) at org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:340) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:240) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:470) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:636) This is my java configuration for tomcat JAVA_OPTS="-Djava.awt.headless=true -D64 -server -Xms4096M -Xmx4096M -XX:+UseConcMarkSweepGC -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=5400 -Dcom.sun.management.jmxremote.ss\ l=false -Dcom.sun.management.jmxremote.authenticate=false" Somebody know why these errors happen ?

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  • Unable to compile netmap on Fedora 32 bit

    - by John Elf
    This is the error everytime I try to install netmap: Can someone let me know how to isntall the same on e1000e or ixgbe. I have kernel header and source installed. [root@localhost e1000]# make KSRC=/usr/src/kernels/2.6.35.6-45.fc14.i686/ make -C /usr/src/kernels/2.6.35.6-45.fc14.i686/ M=/media/sf_Shared/netmap-linux/net/e1000 modules make[1]: Entering directory /usr/src/kernels/2.6.35.6-45.fc14.i686' CC [M] /media/sf_Shared/netmap-linux/net/e1000/e1000_main.o /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c: In function ‘e1000_setup_tx_resources’: /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:1485:2: error: implicit declaration of function ‘vzalloc’ /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:1485:20: warning: assignment makes pointer from integer without a cast /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c: In function ‘e1000_setup_rx_resources’: /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:1680:20: warning: assignment makes pointer from integer without a cast /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c: In function ‘e1000_tx_csum’: /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:2780:2: error: implicit declaration of function ‘skb_checksum_start_offset’ /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c: In function ‘e1000_rx_checksum’: /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:3689:2: error: implicit declaration of function ‘skb_checksum_none_assert’ /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c: In function ‘e1000_restore_vlan’: /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:4617:23: error: ‘VLAN_N_VID’ undeclared (first use in this function) /media/sf_Shared/netmap-linux/net/e1000/e1000_main.c:4617:23: note: each undeclared identifier is reported only once for each function it appears in make[2]: *** [/media/sf_Shared/netmap-linux/net/e1000/e1000_main.o] Error 1 make[1]: *** [_module_/media/sf_Shared/netmap-linux/net/e1000] Error 2 make[1]: Leaving directory/usr/src/kernels/2.6.35.6-45.fc14.i686' make: * [all] Error 2

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  • Simplex Noise Help

    - by Alex Larsen
    Im Making A Minecraft Like Gae In XNA C# And I Need To Generate Land With Caves This Is The Code For Simplex I Have /// <summary> /// 1D simplex noise /// </summary> /// <param name="x"></param> /// <returns></returns> public static float Generate(float x) { int i0 = FastFloor(x); int i1 = i0 + 1; float x0 = x - i0; float x1 = x0 - 1.0f; float n0, n1; float t0 = 1.0f - x0 * x0; t0 *= t0; n0 = t0 * t0 * grad(perm[i0 & 0xff], x0); float t1 = 1.0f - x1 * x1; t1 *= t1; n1 = t1 * t1 * grad(perm[i1 & 0xff], x1); // The maximum value of this noise is 8*(3/4)^4 = 2.53125 // A factor of 0.395 scales to fit exactly within [-1,1] return 0.395f * (n0 + n1); } /// <summary> /// 2D simplex noise /// </summary> /// <param name="x"></param> /// <param name="y"></param> /// <returns></returns> public static float Generate(float x, float y) { const float F2 = 0.366025403f; // F2 = 0.5*(sqrt(3.0)-1.0) const float G2 = 0.211324865f; // G2 = (3.0-Math.sqrt(3.0))/6.0 float n0, n1, n2; // Noise contributions from the three corners // Skew the input space to determine which simplex cell we're in float s = (x + y) * F2; // Hairy factor for 2D float xs = x + s; float ys = y + s; int i = FastFloor(xs); int j = FastFloor(ys); float t = (float)(i + j) * G2; float X0 = i - t; // Unskew the cell origin back to (x,y) space float Y0 = j - t; float x0 = x - X0; // The x,y distances from the cell origin float y0 = y - Y0; // For the 2D case, the simplex shape is an equilateral triangle. // Determine which simplex we are in. int i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords if (x0 > y0) { i1 = 1; j1 = 0; } // lower triangle, XY order: (0,0)->(1,0)->(1,1) else { i1 = 0; j1 = 1; } // upper triangle, YX order: (0,0)->(0,1)->(1,1) // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where // c = (3-sqrt(3))/6 float x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords float y1 = y0 - j1 + G2; float x2 = x0 - 1.0f + 2.0f * G2; // Offsets for last corner in (x,y) unskewed coords float y2 = y0 - 1.0f + 2.0f * G2; // Wrap the integer indices at 256, to avoid indexing perm[] out of bounds int ii = i % 256; int jj = j % 256; // Calculate the contribution from the three corners float t0 = 0.5f - x0 * x0 - y0 * y0; if (t0 < 0.0f) n0 = 0.0f; else { t0 *= t0; n0 = t0 * t0 * grad(perm[ii + perm[jj]], x0, y0); } float t1 = 0.5f - x1 * x1 - y1 * y1; if (t1 < 0.0f) n1 = 0.0f; else { t1 *= t1; n1 = t1 * t1 * grad(perm[ii + i1 + perm[jj + j1]], x1, y1); } float t2 = 0.5f - x2 * x2 - y2 * y2; if (t2 < 0.0f) n2 = 0.0f; else { t2 *= t2; n2 = t2 * t2 * grad(perm[ii + 1 + perm[jj + 1]], x2, y2); } // Add contributions from each corner to get the final noise value. // The result is scaled to return values in the interval [-1,1]. return 40.0f * (n0 + n1 + n2); // TODO: The scale factor is preliminary! } public static float Generate(float x, float y, float z) { // Simple skewing factors for the 3D case const float F3 = 0.333333333f; const float G3 = 0.166666667f; float n0, n1, n2, n3; // Noise contributions from the four corners // Skew the input space to determine which simplex cell we're in float s = (x + y + z) * F3; // Very nice and simple skew factor for 3D float xs = x + s; float ys = y + s; float zs = z + s; int i = FastFloor(xs); int j = FastFloor(ys); int k = FastFloor(zs); float t = (float)(i + j + k) * G3; float X0 = i - t; // Unskew the cell origin back to (x,y,z) space float Y0 = j - t; float Z0 = k - t; float x0 = x - X0; // The x,y,z distances from the cell origin float y0 = y - Y0; float z0 = z - Z0; // For the 3D case, the simplex shape is a slightly irregular tetrahedron. // Determine which simplex we are in. int i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords int i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords /* This code would benefit from a backport from the GLSL version! */ if (x0 >= y0) { if (y0 >= z0) { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // X Y Z order else if (x0 >= z0) { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 0; k2 = 1; } // X Z Y order else { i1 = 0; j1 = 0; k1 = 1; i2 = 1; j2 = 0; k2 = 1; } // Z X Y order } else { // x0<y0 if (y0 < z0) { i1 = 0; j1 = 0; k1 = 1; i2 = 0; j2 = 1; k2 = 1; } // Z Y X order else if (x0 < z0) { i1 = 0; j1 = 1; k1 = 0; i2 = 0; j2 = 1; k2 = 1; } // Y Z X order else { i1 = 0; j1 = 1; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // Y X Z order } // A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z), // a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and // a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where // c = 1/6. float x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords float y1 = y0 - j1 + G3; float z1 = z0 - k1 + G3; float x2 = x0 - i2 + 2.0f * G3; // Offsets for third corner in (x,y,z) coords float y2 = y0 - j2 + 2.0f * G3; float z2 = z0 - k2 + 2.0f * G3; float x3 = x0 - 1.0f + 3.0f * G3; // Offsets for last corner in (x,y,z) coords float y3 = y0 - 1.0f + 3.0f * G3; float z3 = z0 - 1.0f + 3.0f * G3; // Wrap the integer indices at 256, to avoid indexing perm[] out of bounds int ii = i % 256; int jj = j % 256; int kk = k % 256; // Calculate the contribution from the four corners float t0 = 0.6f - x0 * x0 - y0 * y0 - z0 * z0; if (t0 < 0.0f) n0 = 0.0f; else { t0 *= t0; n0 = t0 * t0 * grad(perm[ii + perm[jj + perm[kk]]], x0, y0, z0); } float t1 = 0.6f - x1 * x1 - y1 * y1 - z1 * z1; if (t1 < 0.0f) n1 = 0.0f; else { t1 *= t1; n1 = t1 * t1 * grad(perm[ii + i1 + perm[jj + j1 + perm[kk + k1]]], x1, y1, z1); } float t2 = 0.6f - x2 * x2 - y2 * y2 - z2 * z2; if (t2 < 0.0f) n2 = 0.0f; else { t2 *= t2; n2 = t2 * t2 * grad(perm[ii + i2 + perm[jj + j2 + perm[kk + k2]]], x2, y2, z2); } float t3 = 0.6f - x3 * x3 - y3 * y3 - z3 * z3; if (t3 < 0.0f) n3 = 0.0f; else { t3 *= t3; n3 = t3 * t3 * grad(perm[ii + 1 + perm[jj + 1 + perm[kk + 1]]], x3, y3, z3); } // Add contributions from each corner to get the final noise value. // The result is scaled to stay just inside [-1,1] return 32.0f * (n0 + n1 + n2 + n3); // TODO: The scale factor is preliminary! } private static byte[] perm = new byte[512] { 151,160,137,91,90,15, 131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23, 190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33, 88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166, 77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244, 102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196, 135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123, 5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42, 223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9, 129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228, 251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107, 49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254, 138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180, 151,160,137,91,90,15, 131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23, 190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33, 88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166, 77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244, 102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196, 135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123, 5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42, 223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9, 129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228, 251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107, 49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254, 138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180 }; private static int FastFloor(float x) { return (x > 0) ? ((int)x) : (((int)x) - 1); } private static float grad(int hash, float x) { int h = hash & 15; float grad = 1.0f + (h & 7); // Gradient value 1.0, 2.0, ..., 8.0 if ((h & 8) != 0) grad = -grad; // Set a random sign for the gradient return (grad * x); // Multiply the gradient with the distance } private static float grad(int hash, float x, float y) { int h = hash & 7; // Convert low 3 bits of hash code float u = h < 4 ? x : y; // into 8 simple gradient directions, float v = h < 4 ? y : x; // and compute the dot product with (x,y). return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -2.0f * v : 2.0f * v); } private static float grad(int hash, float x, float y, float z) { int h = hash & 15; // Convert low 4 bits of hash code into 12 simple float u = h < 8 ? x : y; // gradient directions, and compute dot product. float v = h < 4 ? y : h == 12 || h == 14 ? x : z; // Fix repeats at h = 12 to 15 return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -v : v); } private static float grad(int hash, float x, float y, float z, float t) { int h = hash & 31; // Convert low 5 bits of hash code into 32 simple float u = h < 24 ? x : y; // gradient directions, and compute dot product. float v = h < 16 ? y : z; float w = h < 8 ? z : t; return ((h & 1) != 0 ? -u : u) + ((h & 2) != 0 ? -v : v) + ((h & 4) != 0 ? -w : w); } This Is My World Generation Code Block[,] BlocksInMap = new Block[1024, 256]; public bool IsWorldGenerated = false; Random r = new Random(); private void RunThread() { for (int BH = 0; BH <= 256; BH++) { for (int BW = 0; BW <= 1024; BW++) { Block b = new Block(); if (BH >= 192) { } BlocksInMap[BW, BH] = b; } } IsWorldGenerated = true; } public void GenWorld() { new Thread(new ThreadStart(RunThread)).Start(); } And This Is A Example Of How I Set Blocks Block b = new Block(); b.BlockType = = Block.BlockTypes.Air; This Is A Example Of How I Set Models foreach (Block b in MyWorld) { switch(b.BlockType) { case Block.BlockTypes.Dirt: b.Model = DirtModel; break; ect. } } How Would I Use These To Generate To World (The Block Array) And If Possible Thread It More? btw It's 1024 Wide And 256 Tall

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  • Using custom std::set comparator

    - by Omry
    I am trying to change the default order of the items in a set of integers to be lexicographic instead of numeric, and I can't get the following to compile with g++: file.cpp: bool lex_compare(const int64_t &a, const int64_t &b) { stringstream s1,s2; s1 << a; s2 << b; return s1.str() < s2.str(); } void foo() { set<int64_t, lex_compare> > s; s.insert(1); ... } I get the following error: error: type/value mismatch at argument 2 in template parameter list for ‘template<class _Key, class _Compare, class _Alloc> class std::set’ error: expected a type, got ‘lex_compare’ what am I doing wrong?

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  • WPF ComboBox Binding to non string object

    - by Mike L
    I'm using MVVM (MVVM Light Toolkit) and have a property on the view model which exposes a list of objects. The objects contain two properties, both strings, which correlate to an abbreviation and a description. I want the ComboBox to expose the pairing as "abbreviation - description". If I use a data template, it does this easily. I have another property on the view model which represents the object that should display as selected -- the chosen item in the ComboBox. I'm binding the ItemsSource to the list, as it represents the universe of available selections, and am trying to bind the SelectedItem to this object. I'm killing myself trying to figure out why I can't get it to work, and feeling more like a fraud by the hour. In trying to learn why this works, I created the same approach with just a list of strings, and a selected string. This works perfectly. So, it clearly has something to do with the typing... perhaps something in choosing equality? Or perhaps it has to do with the data template? Here is the XAML: <Window x:Class="MvvmLight1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="300" Width="300" DataContext="{Binding Main, Source={StaticResource Locator}}"> <Window.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="Skins/MainSkin.xaml" /> </ResourceDictionary.MergedDictionaries> <DataTemplate x:Key="DataTemplate1"> <StackPanel Orientation="Horizontal"> <TextBlock TextWrapping="Wrap" Text="{Binding CourtCode}"/> <TextBlock TextWrapping="Wrap" Text=" - "/> <TextBlock TextWrapping="Wrap" Text="{Binding CourtDescription}"/> </StackPanel> </DataTemplate> </ResourceDictionary> </Window.Resources> <Grid x:Name="LayoutRoot"> <ComboBox x:Name="cmbAbbrevDescriptions" Height="35" Margin="25,75,25,25" VerticalAlignment="Top" ItemsSource="{Binding Codes}" ItemTemplate="{DynamicResource DataTemplate1}" SelectedItem="{Binding selectedCode}" /> <ComboBox x:Name="cmbStrings" Height="35" Margin="25" VerticalAlignment="Top" ItemsSource="{Binding strs}" SelectedItem="{Binding selectedStr}"/> </Grid> </Window> And, if helpful, here is the ViewModel: using GalaSoft.MvvmLight; using MvvmLight1.Model; using System.Collections.Generic; namespace MvvmLight1.ViewModel { public class MainViewModel : ViewModelBase { public const string CodesPropertyName = "Codes"; private List<Court> _codes = null; public List<Court> Codes { get { return _codes; } set { if (_codes == value) { return; } var oldValue = _codes; _codes = value; // Update bindings and broadcast change using GalaSoft.Utility.Messenging RaisePropertyChanged(CodesPropertyName, oldValue, value, true); } } public const string selectedCodePropertyName = "selectedCode"; private Court _selectedCode = null; public Court selectedCode { get { return _selectedCode; } set { if (_selectedCode == value) { return; } var oldValue = _selectedCode; _selectedCode = value; // Update bindings and broadcast change using GalaSoft.Utility.Messenging RaisePropertyChanged(selectedCodePropertyName, oldValue, value, true); } } public const string strsPropertyName = "strs"; private List<string> _strs = null; public List<string> strs { get { return _strs; } set { if (_strs == value) { return; } var oldValue = _strs; _strs = value; // Update bindings and broadcast change using GalaSoft.Utility.Messenging RaisePropertyChanged(strsPropertyName, oldValue, value, true); } } public const string selectedStrPropertyName = "selectedStr"; private string _selectedStr = ""; public string selectedStr { get { return _selectedStr; } set { if (_selectedStr == value) { return; } var oldValue = _selectedStr; _selectedStr = value; // Update bindings and broadcast change using GalaSoft.Utility.Messenging RaisePropertyChanged(selectedStrPropertyName, oldValue, value, true); } } /// <summary> /// Initializes a new instance of the MainViewModel class. /// </summary> public MainViewModel() { Codes = new List<Court>(); Court code1 = new Court(); code1.CourtCode = "ABC"; code1.CourtDescription = "A Court"; Court code2 = new Court(); code2.CourtCode = "DEF"; code2.CourtDescription = "Second Court"; Codes.Add(code1); Codes.Add(code2); Court code3 = new Court(); code3.CourtCode = "DEF"; code3.CourtDescription = "Second Court"; selectedCode = code3; selectedStr = "Hello"; strs = new List<string>(); strs.Add("Goodbye"); strs.Add("Hello"); strs.Add("Ciao"); } } } And here is the ridiculously trivial class that is being exposed: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace MvvmLight1.Model { public class Court { public string CourtCode { get; set; } public string CourtDescription { get; set; } } } Thanks!

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  • C# Secure Sockets (SSL)

    - by Matthias Vance
    LS, I was planning on writing a wrapper around the System.Net.Sockets.Socket class, because I didn't feel like using the SSLStream class because I wanted to maintain backwards compatibility with other programs. I found an article which does exactly what I want, but on Windows Mobile. (Link: Enable SSL for managed socket on windows mobile) Quote: My first surprise was that SetSocketOption takes a SocketOptionName enum value as the second parameter, but this enum doesn’t have the equivalent of SO_SECURE. However, C# was nice enough to let me cast an arbitrary integer value to the enum I needed. I tried to do the same, but it doesn't work. Code: private const ushort SO_SECURE = 0x2001; private const ushort SO_SEC_SSL = 0x2004; this.SetSocketOption(SocketOptionLevel.Socket, (SocketOptionName) SO_SECURE, SO_SEC_SSL); Error: An unknown, invalid, or unsupported option or level was specified in a getsockopt or setsockopt call Is there a way to work around this? Kind regards, Matthias Vance

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  • how to instantiate template of template

    - by aaa
    hello I have template that looks like this: 100 template<size_t A0, size_t A1, size_t A2, size_t A3> 101 struct mask { 103 template<size_t B0, size_t B1, size_t B2, size_t B3> 104 struct compare { 105 static const bool value = (A0 == B0 && A1 == B1 && A2 == B2 && A3 == B3); 106 }; 107 }; ... 120 const typename boost::enable_if_c< 121 mask<a,b,c,d>::compare<2,3,0,1>::value || ...>::type I am trying to instantiate compare structure. How do I do get value in line 121?

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  • What should I do about this random iPhone crash in WebCore?

    - by xtravar
    This happens at random intervals. Any ideas would be appreciated. Obviously it has to do with the UIWebView, but not sure what's going on. Thread 1 Crashed: 0 WebCore 0x0006eb56 WebCore::ScrollView::repaintContentRectangle(WebCore::IntRect const&, bool) + 10 1 WebCore 0x0005ad88 WebCore::FrameView::doDeferredRepaints() + 32 2 WebCore 0x0005ad00 WebCore::FrameView::endDeferredRepaints() + 104 3 WebCore 0x00050818 WebCore::FrameView::layout(bool) + 844 4 WebCore 0x000504c4 WebCore::FrameView::layoutTimerFired(WebCore::Timer<WebCore::FrameView>*) + 4 5 WebCore 0x000504ae WebCore::Timer<WebCore::FrameView>::fired() + 26 6 WebCore 0x000502c6 WebCore::TimerBase::fireTimers(double, WTF::Vector<WebCore::TimerBase*, 0ul> const&) + 102 7 WebCore 0x0004fd1e WebCore::TimerBase::sharedTimerFired() + 66 8 WebCore 0x0004fcb2 WebCore::timerFired(__CFRunLoopTimer*, void*) + 34 9 CoreFoundation 0x00056bac CFRunLoopRunSpecific + 2112 10 CoreFoundation 0x00056356 CFRunLoopRunInMode + 42 11 WebCore 0x0005d6b2 RunWebThread(void*) + 286 12 libSystem.B.dylib 0x0002490a _pthread_body + 10

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  • C++ Preprocessor string literal concatenation

    - by ezpz
    I found this regarding how the C preprocessor should handle string literal concatenation (phase 6). However, I can not find anything regarding how this is handled in C++ (does C++ use the C preprocessor?). The reason I ask is that I have the following: const char * Foo::encoding = "\0" "1234567890\0abcdefg"; where encoding is a static member of class Foo. Without the availability of concatenation I wouldnt be able to write that sequence of characters like that. const char * Foo::encoding = "\01234567890\0abcdefg"; Is something entirely different due to the way \012 is interpreted. I dont have access to multiple platforms and I'm curious how confident I should be that the above is always handled correctly - i.e. I will always get { 0, '1', '2', '3', ... }

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  • Sort list using stl sort function

    - by Vlad
    I'm trying to sort a list (part of a class) in descending containg items of a struct but it doesn't compile(error: no match for 'operator-' in '__last - __first'): sort(Result.poly.begin(), Result.poly.end(), SortDescending()); And here's SortDescending: struct SortDescending { bool operator()(const term& t1, const term& t2) { return t2.pow < t1.pow; } }; Can anyone tell me what's wrong? Thanks!

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  • How to programmatically open the application menu in a .NET CF 2.0 application

    - by PabloG
    I'm developing an C# / .NET CF 2.0 application: it's supposed to be used with the touchscreen deactivated, then, I'm looking for a way to programmatically open the application menu (not the Windows menu). Looking here I tried to adapt the code to the .NET CF 2 but it doesn't work (no error messages neither) public const int WM_SYSCOMMAND = 0x0112; public const int SC_KEYMENU = 0xF100; private void cmdMenu_Click(object sender, EventArgs e) { Message msg = Message.Create(this.Handle, WM_SYSCOMMAND, new IntPtr(SC_KEYMENU), IntPtr.Zero); MessageWindow.SendMessage(ref msg); } Any ideas? TIA, Pablo After Hans answer, I edited the code to Message msg = Message.Create(this.Handle, WM_SYSCOMMAND, new IntPtr(SC_KEYMENU), new IntPtr(115)); // 's' key and added a submenu option as &Search, but it doesn't make any difference

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  • IXmlSerializable Dictionary

    - by Shimmy
    I was trying to create a generic Dictionary that implements IXmlSerializable. Here is my trial: Sub Main() Dim z As New SerializableDictionary(Of String, String) z.Add("asdf", "asd") Console.WriteLine(z.Serialize) End Sub Result: <?xml version="1.0" encoding="utf-16"?><Entry key="asdf" value="asd" /> I placed a breakpoint on top of the WriteXml method and I see that when it stops, the writer contains no data at all, and IMHO it should contain the root element and the xml declaration. <Serializable()> _ Public Class SerializableDictionary(Of TKey, TValue) : Inherits Dictionary(Of TKey, TValue) : Implements IXmlSerializable Private Const EntryString As String = "Entry" Private Const KeyString As String = "key" Private Const ValueString As String = "value" Private Shared ReadOnly AttributableTypes As Type() = New Type() {GetType(Boolean), GetType(Byte), GetType(Char), GetType(DateTime), GetType(Decimal), GetType(Double), GetType([Enum]), GetType(Guid), GetType(Int16), GetType(Int32), GetType(Int64), GetType(SByte), GetType(Single), GetType(String), GetType(TimeSpan), GetType(UInt16), GetType(UInt32), GetType(UInt64)} Private Shared ReadOnly GetIsAttributable As Predicate(Of Type) = Function(t) AttributableTypes.Contains(t) Private Shared ReadOnly IsKeyAttributable As Boolean = GetIsAttributable(GetType(TKey)) Private Shared ReadOnly IsValueAttributable As Boolean = GetIsAttributable(GetType(TValue)) Private Shared ReadOnly GetElementName As Func(Of Boolean, String) = Function(isKey) If(isKey, KeyString, ValueString) Public Function GetSchema() As System.Xml.Schema.XmlSchema Implements System.Xml.Serialization.IXmlSerializable.GetSchema Return Nothing End Function Public Sub WriteXml(ByVal writer As XmlWriter) Implements IXmlSerializable.WriteXml For Each entry In Me writer.WriteStartElement(EntryString) WriteData(IsKeyAttributable, writer, True, entry.Key) WriteData(IsValueAttributable, writer, False, entry.Value) writer.WriteEndElement() Next End Sub Private Sub WriteData(Of T)(ByVal attributable As Boolean, ByVal writer As XmlWriter, ByVal isKey As Boolean, ByVal value As T) Dim name = GetElementName(isKey) If attributable Then writer.WriteAttributeString(name, value.ToString) Else Dim serializer As New XmlSerializer(GetType(T)) writer.WriteStartElement(name) serializer.Serialize(writer, value) writer.WriteEndElement() End If End Sub Public Sub ReadXml(ByVal reader As XmlReader) Implements IXmlSerializable.ReadXml Dim empty = reader.IsEmptyElement reader.Read() If empty Then Exit Sub Clear() While reader.NodeType <> XmlNodeType.EndElement While reader.NodeType = XmlNodeType.Whitespace reader.Read() Dim key = ReadData(Of TKey)(IsKeyAttributable, reader, True) Dim value = ReadData(Of TValue)(IsValueAttributable, reader, False) Add(key, value) If Not IsKeyAttributable AndAlso Not IsValueAttributable Then reader.ReadEndElement() Else reader.Read() While reader.NodeType = XmlNodeType.Whitespace reader.Read() End While End While reader.ReadEndElement() End While End Sub Private Function ReadData(Of T)(ByVal attributable As Boolean, ByVal reader As XmlReader, ByVal isKey As Boolean) As T Dim name = GetElementName(isKey) Dim type = GetType(T) If attributable Then Return Convert.ChangeType(reader.GetAttribute(name), type) Else Dim serializer As New XmlSerializer(type) While reader.Name <> name reader.Read() End While reader.ReadStartElement(name) Dim value = serializer.Deserialize(reader) reader.ReadEndElement() Return value End If End Function Public Shared Function Serialize(ByVal dictionary As SerializableDictionary(Of TKey, TValue)) As String Dim sb As New StringBuilder(1024) Dim sw As New StringWriter(sb) Dim xs As New XmlSerializer(GetType(SerializableDictionary(Of TKey, TValue))) xs.Serialize(sw, dictionary) sw.Dispose() Return sb.ToString End Function Public Shared Function Deserialize(ByVal xml As String) As SerializableDictionary(Of TKey, TValue) Dim xs As New XmlSerializer(GetType(SerializableDictionary(Of TKey, TValue))) Dim xr As New XmlTextReader(xml, XmlNodeType.Document, Nothing) Return xs.Deserialize(xr) xr.Close() End Function Public Function Serialize() As String Dim sb As New StringBuilder Dim xw = XmlWriter.Create(sb) WriteXml(xw) xw.Close() Return sb.ToString End Function Public Sub Parse(ByVal xml As String) Dim xr As New XmlTextReader(xml, XmlNodeType.Document, Nothing) ReadXml(xr) xr.Close() End Sub End Class

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  • Can't define static abstract string property

    - by goombaloon
    I've run into an interesting problem and am looking for some suggestions on how best to handle this... I have an abstract class that contains a static method that accepts a static string that I would like to define as an abstract property. Problem is that C# doesn't doesn't support the following (see the ConfigurationSectionName and Current properties): public abstract class ProviderConfiguration : ConfigurationSection { private const string _defaultProviderPropertyName = "defaultProvider"; private const string _providersPropertyName = "providers"; protected static string ConfigurationSectionName { get; } public static Configuration Current { get { return Configuration)ConfigurationManager.GetSection(ConfigurationSectionName); } } } I suppose one way to handle this would be to make ConfigurationSectionName NOT abstract and then create a new definition of ConfigurationSectionName in the derived classes, but that feels pretty hackish. Any suggestions would be most welcome. Gratias!!!

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  • C++ / error LNK2019 - XpokerEval library

    - by user1068115
    I have been struggling all the afternoon with the XPokerEval Library I downloaded here: http://www.codingthewheel.com/archives/poker-hand-evaluator-roundup#xpokereval I am trying to make the XPokerEval.PokerSim work, using Visual C++ 2010 express but i get the following errors: 1>psim_test.obj : error LNK2019: unresolved external symbol "void __cdecl SimulateHand(char const *,struct SimResults *,float,float,unsigned int)" (?SimulateHand@@YAXPBDPAUSimResults@@MMI@Z) referenced in function _wmain 1>psim_test.obj : error LNK2019: unresolved external symbol "unsigned int __cdecl RankHand(int const *)" (?RankHand@@YAIPBH@Z) referenced in function _wmain Do you think this can be due to a missing link to a library or a incompatibility with my IDE? The script uses the Pokersource Poker-Eval library which is also included in the zip file, I added to the project directories but it still does not work! I cannot figure out why and I am getting mad! Thanks in advance for any tips on this!

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  • Memory allocation in case of static variables

    - by eSKay
    I am always confused about static variables, and the way memory allocation happens for them. For example: int a = 1; const int b = 2; static const int c = 3; int foo(int &arg){ arg++; return arg; } How is the memory allocated for a,b and c? What is the difference (in terms of memory) if I call foo(a), foo(b) and foo(c)?

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  • Compilation error when using boost serialization library

    - by Shakir
    I have been struggling with this error for a long time. The following is my code snippet. //This is the header file template<typename TElem> class ArrayList { public: /** An accessible typedef for the elements in the array. */ typedef TElem Elem; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & ptr_; ar & size_; ar & cap_; } Elem *ptr_; // the stored or aliased array index_t size_; // number of active objects index_t cap_; // allocated size of the array; -1 if alias }; template <typename TElem> class gps_position { public: typedef TElem Elem; friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & degrees; ar & minutes; ar & seconds; } private: Elem degrees; index_t minutes; index_t seconds; }; // This is the .cc file #include #include #include #include #include #include #include #include #include "arraylist.h" int main() { // create and open a character archive for output std::ofstream ofs("filename"); // create class instance // gps_position<int> g(35.65, 59, 24.567f); gps_position<float> g; // save data to archive { boost::archive::text_oarchive oa(ofs); // write class instance to archive //oa << g; // archive and stream closed when destructors are called } // ... some time later restore the class instance to its orginal state /* gps_position<int> newg; { // create and open an archive for input std::ifstream ifs("filename"); boost::archive::text_iarchive ia(ifs); // read class state from archive ia >> newg; // archive and stream closed when destructors are called }*/ ArrayList<float> a1; ArrayList<int> a2; a1.Init(22); a2.Init(21); // a1.Resize(30); // a1.Resize(12); // a1.Resize(22); // a2.Resize(22); a1[21] = 99.0; a1[20] = 88.0; for (index_t i = 0; i < a1.size(); i++) { a1[i] = i; a1[i]++; } std::ofstream s("test.txt"); { boost::archive::text_oarchive oa(s); oa << a1; } return 0; } The following is the compilation error i get. In file included from /usr/include/boost/serialization/split_member.hpp:23, from /usr/include/boost/serialization/nvp.hpp:33, from /usr/include/boost/serialization/serialization.hpp:17, from /usr/include/boost/archive/detail/oserializer.hpp:61, from /usr/include/boost/archive/detail/interface_oarchive.hpp:24, from /usr/include/boost/archive/detail/common_oarchive.hpp:20, from /usr/include/boost/archive/basic_text_oarchive.hpp:32, from /usr/include/boost/archive/text_oarchive.hpp:31, from demo.cc:4: /usr/include/boost/serialization/access.hpp: In static member function ‘static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = float]’: /usr/include/boost/serialization/serialization.hpp:74: instantiated from ‘void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = float]’ /usr/include/boost/serialization/serialization.hpp:133: instantiated from ‘void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive, T = float]’ /usr/include/boost/archive/detail/oserializer.hpp:140: instantiated from ‘void boost::archive::detail::oserializer<Archive, T>::save_object_data(boost::archive::detail::basic_oarchive&, const void*) const [with Archive = boost::archive::text_oarchive, T = float]’ demo.cc:105: instantiated from here /usr/include/boost/serialization/access.hpp:109: error: request for member ‘serialize’ in ‘t’, which is of non-class type ‘float’ Please help me out.

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  • GSL-GNU in Visual studio

    - by Arman
    I have visual studio 2008, I want to integrate GSL library in my project, kindly give me some guidelines so that I can make it possible. I have added the GSL library but the following error come. Error 1 error LNK2028: unresolved token (0A000010) "extern "C" void __cdecl gsl_matrix_set(struct gsl_matrix *,unsigned int,unsigned int,double)" (?gsl_matrix_set@@$$J0YAXPAUgsl_matrix@@IIN@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 2 error LNK2028: unresolved token (0A000011) "extern "C" struct gsl_matrix * __cdecl gsl_matrix_alloc(unsigned int,unsigned int)" (?gsl_matrix_alloc@@$$J0YAPAUgsl_matrix@@II@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 3 error LNK2028: unresolved token (0A000014) "extern "C" double __cdecl gsl_matrix_get(struct gsl_matrix const *,unsigned int,unsigned int)" (?gsl_matrix_get@@$$J0YANPBUgsl_matrix@@II@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 4 error LNK2019: unresolved external symbol "extern "C" double __cdecl gsl_matrix_get(struct gsl_matrix const *,unsigned int,unsigned int)" (?gsl_matrix_get@@$$J0YANPBUgsl_matrix@@II@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ) Error 5 error LNK2019: unresolved external symbol "extern "C" void __cdecl gsl_matrix_set(struct gsl_matrix *,unsigned int,unsigned int,double)" (?gsl_matrix_set@@$$J0YAXPAUgsl_matrix@@IIN@Z) referenced in function "int __cdecl main(void)" (?main@@$$HYAHXZ)

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  • Difference between Singleton implemention using pointer and using static object

    - by Anon
    EDIT: Sorry my question was not clear, why do books/articles prefer implementation#1 over implementation#2? What is the actual advantage of using pointer in implementation of Singleton class vs using a static object? Why do most books prefer this class Singleton { private: static Singleton *p_inst; Singleton(); public: static Singleton * instance() { if (!p_inst) { p_inst = new Singleton(); } return p_inst; } }; over this class Singleton { public: static Singleton& Instance() { static Singleton inst; return inst; } protected: Singleton(); // Prevent construction Singleton(const Singleton&); // Prevent construction by copying Singleton& operator=(const Singleton&); // Prevent assignment ~Singleton(); // Prevent unwanted destruction };

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