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• Strange Matlab error: "??? Subscript indices must either be real positive integers or logicals"

  - by Roee Adler

  I have a function func that returns a vector a. I usually plot a and then perform further analysis on it. I have a certain scenario when once I try to plot a, I get a "??? Subscript indices must either be real positive integers or logicals" error. Take a look at the following piece of code to see the vector's behavior: K>> a a = 5.7047 6.3529 6.4826 5.5750 4.1488 5.8343 5.3157 5.4454 K>> plot(a) ??? Subscript indices must either be real positive integers or logicals. K>> for i=1:length(a); b(i) = a(i); end; K>> b b = 5.7047 6.3529 6.4826 5.5750 4.1488 5.8343 5.3157 5.4454 K>> plot(b) ??? Subscript indices must either be real positive integers or logicals. The scenario where this happens is when I call function func from within another function (call it outer_func), and return the result directly as outer_func's result. When debugging inside outer_func, I can plot a properly, but outside the scope of outer_func, its result has the above behavior. What can cause this? Where do I start from?

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• How much effort do you have to put in to get gains from using SSE?

  - by John

  Case One Say you have a little class: class Point3D { private: float x,y,z; public: operator+=() ...etc }; Point3D &Point3D::operator+=(Point3D &other) { this->x += other.x; this->y += other.y; this->z += other.z; } A naive use of SSE would simply replace these function bodies with using a few intrinsics. But would we expect this to make much difference? MMX used to involve costly state cahnges IIRC, does SSE or are they just like other instructions? And even if there's no direct "use SSE" overhead, would moving the values into SSE registers and back out again really make it any faster? Case Two Instead, you're working with a less OO-based code base. Rather than an array/vector of Point3D objects, you simply have a big array of floats: float coordinateData[NUM_POINTS*3]; void add(int i,int j) //yes it's unsafe, no overlap check... example only { for (int x=0;x<3;++x) { coordinateData[i*3+x] += coordinateData[j*3+x]; } } What about use of SSE here? Any better? In conclusion Is trying to optimise single vector operations using SSE actually worthwhile, or is it really only valuable when doing bulk operations?

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• Blackberry invalidate field not causing a repaint

  - by Michaela

  I'm writing a Blackberry app. I have a custom list field where I can select an item in the list which pushes the edit screen onto the stack. I edit the item and save, and when I pop that screen off so I am back on my list screen, I want to view the update I just made reflected in the list. I have done this on other screens which just had LabelFields and it worked fine. However, with the list screen, calling invalidate() seems to do nothing. I know the value has saved correctly through print lines, and I see the paint() method in the listfield is getting called. But the only way I can get the list field to update is to delete it from the screen and re-add it. That seems wrong. What am I doing wrong? public class ListTasksScreen extends MainScreen{ private TaskList tasks; private CustomListField taskListField; public ListTasksScreen (TaskList tasks){ super(); this.tasks = tasks; Vector incompleteTasks = tasks.getIncompleteTasks(); taskListField = new CustomListField(incompleteTasks, tasks); add(taskListField); } public void updateTaskList(TaskList t) { Vector incompleteTasks = t.getIncompleteTasks(); taskListField= new TaskListField(incompletetTasks, t); //I just want to call taskListField.invalidate() here. //the only thing that seems to work is deleting taskListField //and re-adding this.delete(taskListField); add(taskListField); } }

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• What most efficient method to find a that triangle which contains the given point?

  - by Christo

  Given the triangle with vertices (a,b,c): c / \ / \ / \ a - - - b Which is then subdivided into four triangles by halving each of the edges: c / \ / \ ca / \ bc /\ - - - /\ / \ / \ / \ / \ a- - - - ab - - - -b Wich results in four triangles (a, ab, ca), (b, bc, ab), (c, ca, bc), (ab, bc, ca). Now given a point p. How do I determine in which triangle p lies, given that p is within the outer triangle (a, b, c)? Currently I intend to use ab as the origin. Check whether it is to the left of right of the line "ca - ab" using the perp of "ca - ab" and checking the sign against the dot product of "ab - a" and the perp vector and the vector "p - ab". If it is the same or the dot product is zero then it must be in (a, ab, ca)... Continue with this procedure with the other outer triangles (b, ba, ab) & (c, ca, ba). In the end if it didn't match with these it must be contained within the inner triangle (ab, bc, ca). Is there a better way to do it?

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• Large flags enumerations in C#

  - by LorenVS

  Hey everyone, got a quick question that I can't seem to find anything about... I'm working on a project that requires flag enumerations with a large number of flags (up to 40-ish), and I don't really feel like typing in the exact mask for each enumeration value: public enum MyEnumeration : ulong { Flag1 = 1, Flag2 = 2, Flag3 = 4, Flag4 = 8, Flag5 = 16, // ... Flag16 = 65536, Flag17 = 65536 * 2, Flag18 = 65536 * 4, Flag19 = 65536 * 8, // ... Flag32 = 65536 * 65536, Flag33 = 65536 * 65536 * 2 // right about here I start to get really pissed off } Moreover, I'm also hoping that there is an easy(ier) way for me to control the actual arrangement of bits on different endian machines, since these values will eventually be serialized over a network: public enum MyEnumeration : uint { Flag1 = 1, // BIG: 0x00000001, LITTLE:0x01000000 Flag2 = 2, // BIG: 0x00000002, LITTLE:0x02000000 Flag3 = 4, // BIG: 0x00000004, LITTLE:0x03000000 // ... Flag9 = 256, // BIG: 0x00000010, LITTLE:0x10000000 Flag10 = 512, // BIG: 0x00000011, LITTLE:0x11000000 Flag11 = 1024 // BIG: 0x00000012, LITTLE:0x12000000 } So, I'm kind of wondering if there is some cool way I can set my enumerations up like: public enum MyEnumeration : uint { Flag1 = flag(1), // BOTH: 0x80000000 Flag2 = flag(2), // BOTH: 0x40000000 Flag3 = flag(3), // BOTH: 0x20000000 // ... Flag9 = flag(9), // BOTH: 0x00800000 } What I've Tried: // this won't work because Math.Pow returns double // and because C# requires constants for enum values public enum MyEnumeration : uint { Flag1 = Math.Pow(2, 0), Flag2 = Math.Pow(2, 1) } // this won't work because C# requires constants for enum values public enum MyEnumeration : uint { Flag1 = Masks.MyCustomerBitmaskGeneratingFunction(0) } // this is my best solution so far, but is definitely // quite clunkie public struct EnumWrapper<TEnum> where TEnum { private BitVector32 vector; public bool this[TEnum index] { // returns whether the index-th bit is set in vector } // all sorts of overriding using TEnum as args } Just wondering if anyone has any cool ideas, thanks!

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• How to determine Scale of Line Graph based on Pixels/Height?

  - by Dexter

  I have a problem due to my terrible math abilities, that I cannot figure out how to scale a graph based on the maximum and minimum values so that the whole graph will fit onto the graph-area (400x420) without parts of it being off the screen (based on a given equation by user). Let's say I have this code, and it automatically draws squares and then the line graph based on these values. What is the formula (what do I multiply) to scale it so that it fits into the small graphing area? vector<int> m_x; vector<int> m_y; // gets automatically filled by user equation or values int HeightInPixels = 420;// Graphing area size!! int WidthInPixels = 400; int best_max_y = GetMaxOfVector(m_y); int best_min_y = GetMinOfVector(m_y); m_row = 0; m_col = 0; y_magnitude = (HeightInPixels/(best_max_y+best_min_y)); // probably won't work magnitude = (WidthInPixels/(int)m_x.size()); m_col = m_row = best_max_y; // number of vertical/horizontal lines to draw ////x_magnitude = (WidthInPixels/(int)m_x.size())/2; Doesn't work well ////y_magnitude = (HeightInPixels/(int)m_y.size())/2; Doesn't work well ready = true; // we have values, graph it Invalidate(); // uses WM_PAINT

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• Cann Boost Program_options separate comma separated argument values

  - by lrm

  If my command line is: > prog --mylist=a,b,c Can Boost's program_options be setup to see three distinct argument values for the mylist argument? I have configured program_options as: namespace po = boost::program_options; po::options_description opts("blah") opts.add_options() ("mylist", std::vector<std::string>>()->multitoken, "description"); po::variables_map vm; po::store(po::parse_command_line(argc, argv, opts), vm); po::notify(vm); When I check the value of the mylist argument, I see one value as a,b,c. I'd like to see three distinct values, split on comma. This works fine if I specify the command line as: > prog --mylist=a b c or > prog --mylist=a --mylist=b --mylist=c Is there a way to configure program_options so that it sees a,b,c as three values that should each be inserted into the vector, rather than one? I am using boost 1.41, g++ 4.5.0 20100520, and have enabled c++0x experimental extensions.

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• JTable Insert row and refresh

  - by user269723

  Hi All, I am trying to create simple application where JTable gets updated and refreshed after data is changed.Structure is as follows. 1)Class Main which contains JFrame,JTable details. 2)SampleTableModel class which extends AbstractTableModel.I am overriding most of the methods.`import javax.swing.table.; import javax.swing.event.; import java.util.*; public class SampleTableModel extends AbstractTableModel { public SampleTableModel(){ // this.addTableModelListener( } String[] columnNames = {"A","B","C","D","E"}; int[][] data = {{1,2,3,4,5},{5,6,7,8,9},{12,13,14,15,16}}; Vector dataVector = new Vector(); public Object getValueAt(int rowIndex,int columnIndex) { return data[rowIndex][columnIndex]; } public int getColumnCount(){ return 5; } public int getRowCount(){ return 3; } public String getColumnName(int columnIndex){ return columnNames[columnIndex]; } public void setValueAt(Object value,int row,int column){ data[row][column] =99; } public void notifyTable(AEMessage message){ /* * This method will be called from another class to update JTable. * */ data[0][1]=999; data[0][2]=8838; data[1][1]=8883; fireTableRowsUpdated(0,3); } } ` As you can see, notifyTable will be called from another class(which is actually a thread-which calls this method frequently) Problem is I don't see data being changed in JTable.I see only the initialized data. In the Main class- I am setting like this- RVJDataTable.setModel(new SampleTableModel());

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• Simulated Annealing and Yahtzee!

  - by Jasie

  I've picked up Programming Challenges and found a Yahtzee! problem which I will simplify: There are 13 scoring categories There are 13 rolls by a player (comprising a play) Each roll must fit in a distinct category The goal is to find the maximum score for a play (the optimal placement of rolls in categories); score(play) returns the score for a play Brute-forcing to find the maximum play score requires 13! (= 6,227,020,800) score() calls. I choose simulated annealing to find something close to the highest score, faster. Though not deterministic, it's good enough. I have a list of 13 rolls of 5 die, like: ((1,2,3,4,5) #1 (1,2,6,3,4),#2 ... (1,4,3,2,2) #13 ) And a play (1,5,6,7,2,3,4,8,9,10,13,12,11) passed into score() returns a score for that play's permutation. How do I choose a good "neighboring state"? For random-restart, I can simply choose a random permutation of nos. 1-13, put them in a vector, and score them. In the traveling salesman problem, here's an example of a good neighboring state: "The neighbours of some particular permutation are the permutations that are produced for example by interchanging a pair of adjacent cities." I have a bad feeling about simply swapping two random vector positions, like so: (1,5,6,7, 2 , 3,4,8,9,10, 13, 12,11) # switch 2 and 13 (1,5,6,7, 13, 3,4,8,9,10, 2 , 12,11) # now score this one But I have no evidence and don't know how to select a good neighboring state. Anyone have any ideas on how to pick good neighboring states?

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• c++ function scope

  - by Myx

  I have a main function in A.cpp which has the following relevant two lines of code: B definition(input_file); definition.Print(); In B.h I have the following relevant lines of code: class B { public: // Constructors B(void); B(const char *filename); ~B(void); // File input int ParseLSFile(const char *filename); // Debugging void Print(void); // Data int var1; double var2; vector<char* > var3; map<char*, vector<char* > > var4; } In B.cpp, I have the following function signatures (sorry for being redundant): B::B(void) : var1(-1), var2(numeric_limits<double>::infinity()) { } B::B(const char *filename) { B *def = new B(); def->ParseLSFile(filename); } B::~B(void) { // Free memory for var3 and var 4 } int B::ParseLSFile(const char *filename) { // assign var1, var2, var3, and var4 values } void B::Print(void) { // print contents of var1, var2, var3, and var4 to stdout } So when I call Print() from within B::ParseLSFile(...), then the contents of my structures print correctly to stdout. However, when I call definition.Print() from A.cpp, my structures are empty or contain garbage. Can anyone recommend the correct way to initialize/pass my structures so that I can access them outside of the scope of my function definition? Thanks.

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• dealing cards in Clojure

  - by Ralph

  I am trying to write a Spider Solitaire player as an exercise in learning Clojure. I am trying to figure out how to deal the cards. I have created (with the help of stackoverflow), a shuffled sequence of 104 cards from two standard decks. Each card is represented as a (defstruct card :rank :suit :face-up) The tableau for Spider will be represented as follows: (defstruct tableau :stacks :complete) where :stacks is a vector of card vectors, 4 of which contain 5 cards face down and 1 card face up, and 6 of which contain 4 cards face down and 1 card face up, for a total of 54 cards, and :complete is an (initially) empty vector of completed sets of ace-king (represented as, for example, king-hearts, for printing purposes). The remainder of the undealt deck should be saved in a ref (def deck (ref seq)) During the game, a tableau may contain, for example: (struct-map tableau :stacks [[AH 2C KS ...] [6D QH JS ...] ... ] :complete [KC KS]) where "AH" is a card containing {:rank :ace :suit :hearts :face-up false}, etc. How can I write a function to deal the stacks and then save the remainder in the ref?

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• Boost binding a function taking a reference

  - by Jamie Cook

  Hi all, I am having problems compiling the following snippet int temp; vector<int> origins; vector<string> originTokens = OTUtils::tokenize(buffer, ","); // buffer is a char[] array // original loop BOOST_FOREACH(string s, originTokens) { from_string(temp, s); origins.push_back(temp); } // I'd like to use this to replace the above loop std::transform(originTokens.begin(), originTokens.end(), origins.begin(), boost::bind<int>(&FromString<int>, boost::ref(temp), _1)); where the function in question is // the third parameter should be one of std::hex, std::dec or std::oct template <class T> bool FromString(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec) { std::istringstream iss(s); return !(iss >> f >> t).fail(); } the error I get is 1>Compiling with Intel(R) C++ 11.0.074 [IA-32]... (Intel C++ Environment) 1>C:\projects\svn\bdk\Source\deps\boost_1_42_0\boost/bind/bind.hpp(303): internal error: assertion failed: copy_default_arg_expr: rout NULL, no error (shared/edgcpfe/il.c, line 13919) 1> 1> return unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]); 1> ^ 1> 1>icl: error #10298: problem during post processing of parallel object compilation Google is being unusually unhelpful so I hope that some one here can provide some insights.

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• Problem in Building mplsh-run in lshkit

  - by Yijinsei

  Hi guy, been trying out this for quite some time but I'm still unable to built mplsh-run from lshkit Not sure if this would help to explain my situation during the building process /tmp/cc17kth4.o: In function `lshkit::MultiProbeLshRecallTable::reset(lshkit::MultiProbeLshModel, unsigned int, double, double)': mplsh-run.cpp:(.text._ZN6lshkit24MultiProbeLshRecallTable5resetENS_18MultiProbeLshModelEjdd[lshkit::MultiProbeLshRecallTable::reset(lshkit::MultiProbeLshModel, unsigned int, double, double)]+0x230): undefined reference to `lshkit::MultiProbeLshModel::recall(double) const' /tmp/cc17kth4.o: In function `void lshkit::MultiProbeLshIndex<unsigned int>::query_recall<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, float, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&) const': mplsh-run.cpp:(.text._ZNK6lshkit18MultiProbeLshIndexIjE12query_recallINS_11TopkScannerINS_6MatrixIfE8AccessorENS_6metric5l2sqrIfEEEEEEvPKffRT_[void lshkit::MultiProbeLshIndex<unsigned int>::query_recall<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, float, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&) const]+0x2c4): undefined reference to `lshkit::MultiProbeLsh::genProbeSequence(float const*, std::vector<unsigned int, std::allocator<unsigned int> >&, unsigned int) const' /tmp/cc17kth4.o: In function `void lshkit::MultiProbeLshIndex<unsigned int>::query<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, unsigned int, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&)': mplsh-run.cpp:(.text._ZN6lshkit18MultiProbeLshIndexIjE5queryINS_11TopkScannerINS_6MatrixIfE8AccessorENS_6metric5l2sqrIfEEEEEEvPKfjRT_[void lshkit::MultiProbeLshIndex<unsigned int>::query<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, unsigned int, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&)]+0x4a): undefined reference to `lshkit::MultiProbeLsh::genProbeSequence(float const*, std::vector<unsigned int, std::allocator<unsigned int> >&, unsigned int) const' collect2: ld returned 1 exit status the command that i used to built mplsh-run is g++ -I./lshkit/include -L/usr/lib -lm -lgsl -lgslcblas -lboost_program_options-mt mplsh-run.cpp Do you guys have any clue on how I could solve this?

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• How do I refactor code into a subroutine but allow for early exit?

  - by deworde

  There's a really obvious refactoring opportunity in this (working) code. bool Translations::compatibleNICodes(const Rule& rule, const std::vector<std::string>& nicodes) { bool included = false; // Loop through the ni codes. for(std::vector<std::string> iter = nicodes.begin(); iter != nicodes.end(); ++iter) { // Match against the ni codes of the rule if(rule.get_ni1() == *iter) { // If there's a match, check if the rule is include or exclude const std::string flag = rule.get_op1(); // If include, code is included unless a later rule excludes it if(flag == "INCLUDE"){ included = true; } // If exclude, code is specifically excluded else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni2() == *iter) { const std::string flag = rule.get_op2(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni3() == *iter) { const std::string flag = rule.get_op3(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni4() == *iter) { const std::string flag = rule.get_op4(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } if(rule.get_ni5() == *iter) { const std::string flag = rule.get_op5(); if(flag == "INCLUDE"){ included = true; } else if(flag == "EXCLUDE"){ return false; } } } return included; } The problem is that I can't get around the problem that I want to exit early if it's an exclude statement. Note that I can't change the structure of the Rule class. Any advice?

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• Jboss 6 Cluster Singleton Clustered

  - by DanC

  I am trying to set up a Jboss 6 in a clustered environment, and use it to host clustered stateful singleton EJBs. So far we succesfully installed a Singleton EJB within the cluster, where different entrypoints to our application (through a website deployed on each node) point to a single environment on which the EJB is hosted (thus mantaining the state of static variables). We achieved this using the following configuration: Bean interface: @Remote public interface IUniverse { ... } Bean implementation: @Clustered @Stateful public class Universe implements IUniverse { private static Vector<String> messages = new Vector<String>(); ... } jboss-beans.xml configuration: <deployment xmlns="urn:jboss:bean-deployer:2.0"> <!-- This bean is an example of a clustered singleton --> <bean name="Universe" class="Universe"> </bean> <bean name="UniverseController" class="org.jboss.ha.singleton.HASingletonController"> <property name="HAPartition"><inject bean="HAPartition"/></property> <property name="target"><inject bean="Universe"/></property> <property name="targetStartMethod">startSingleton</property> <property name="targetStopMethod">stopSingleton</property> </bean> </deployment> The main problem for this implementation is that, after the master node (the one that contains the state of the singleton EJB) shuts down gracefuly, the Singleton's state is lost and reset to default. Please note that everything was constructed following the JBoss 5 Clustering documents, as no JBoss 6 documents were found on this subject. Any information on how to solve this problem or where to find JBoss 6 documention on clustering is appreciated.

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• Compilation errors calling find_if using a functor

  - by Jim Wong

  We are having a bit of trouble using find_if to search a vector of pairs for an entry in which the first element of the pair matches a particular value. To make this work, we have defined a trivial functor whose operator() takes a pair as input and compares the first entry against a string. Unfortunately, when we actually add a call to find_if using an instance of our functor constructed using a temporary string value, the compiler produces a raft of error messages. Oddly (to me, anyway), if we replace the temporary with a string that we've created on the stack, things seem to work. Here's what the code (including both versions) looks like: typedef std::pair<std::string, std::string> MyPair; typedef std::vector<MyPair> MyVector; struct MyFunctor: std::unary_function <const MyPair&, bool> { explicit MyFunctor(const std::string& val) : m_val(val) {} bool operator() (const MyPair& p) { return p.first == m_val; } const std::string m_val; }; bool f(const char* s) { MyFunctor f(std::string(s)); // ERROR // std::string str(s); // MyFunctor f(str); // OK MyVector vec; MyVector::const_iterator i = std::find_if(vec.begin(), vec.end(), f); return i != vec.end(); } And here's what the most interesting error message looks like: /usr/include/c++/4.2.1/bits/stl_algo.h:260: error: conversion from ‘std::pair, std::allocator , std::basic_string, std::allocator ’ to non-scalar type ‘std::string’ requested Because we have a workaround, we're mostly curious as to why the first form causes problems. I'm sure we're missing something, but we haven't been able to figure out what it is.

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• Parse string to create a list of element

  - by Nick

  I have a string like this: "\r color=\"red\" name=\"Jon\" \t\n depth=\"8.26\" " And I want to parse this string and create a std::list of this object: class data { std::string name; std::string value; }; Where for example: name = color value = red What is the fastest way? I can use boost. EDIT: This is what i've tried: vector<string> tokens; split(tokens, str, is_any_of(" \t\f\v\n\r")); if(tokens.size() > 1) { list<data> attr; for_each(tokens.begin(), tokens.end(), [&attr](const string& token) { if(token.empty() || !contains(token, "=")) return; vector<string> tokens; split(tokens, token, is_any_of("=")); erase_all(tokens[1], "\""); attr.push_back(data(tokens[0], tokens[1])); } ); } But it does not work if there are spaces inside " ": like color="red 1".

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• Google App Engine how to get an object from the servlet ?

  - by Frank

  I have the following class objects in Google App Engine's dadastore, I can see them from the "Datastore Viewer " : import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) Long Id; public static final long serialVersionUID=26362862L; String Contact_Id="",First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country=""; double D_1,D_2; boolean B_1,B_2; Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } How can my java applications get the object from a servlet url ? For instance if have an instance of Contact_Info_Entry who's Contact_Id is "ABC-123", and my App Id is : nm-java When my java program accesses the url : "http://nm-java.appspot.com/Check_Contact_Info?Contact_Id=ABC-123 How will the Check_Contact_Info servlet get the object from datastore and return it to my app ? public class Check_Contact_Info_Servlet extends HttpServlet { static boolean Debug=true; public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { } ... protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doGet(request,response); } } Frank

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• Why won't this loop normalize my Vector2 list?

  - by ssb

  See the following code: List<Vector2> axes = new List<Vector2>(); axes.Add(TopRight() - TopLeft()); axes.Add(BottomLeft() - TopLeft()); axes.Add(otherRectangle.TopRight() - otherRectangle.TopLeft()); axes.Add(otherRectangle.BottomLeft() - otherRectangle.TopLeft()); // Try normalizing vectors? foreach (Vector2 axis in axes) { axis.Normalize(); } the Vector2.Normalize() method is a void method that normalizes the vector it's called on. Yet for some reason when I do this loop it doesn't normalize the vectors. Am I just unable to modify a list this way? Some oddities: Iterating with a for loop, i.e. axis[i].Normalize() doesn't work. Iterating with the built-in List<T>.ForEach iterator does not work. Creating a normalizing the vector before adding it to the list rather than iterating over the list does work. Why does iteration not work?

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• Why doesn't this for-loop execute?

  - by Maulrus

  I'm writing a program for an exercise that will read data from a file and format it to be readable. So far, I have a bit of code that will separate a header from the data that goes under it. Here it is: int main() { ifstream in("records.txt"); ofstream out("formatted_records.txt"); vector<string> temp; vector<string> headers; for (int i = 0; getline(in,temp[i]); ++i) { static int k = -1; if (str_isalpha(temp[i])) { headers[++k] = temp[i]; temp.erase(temp.begin() + i); } else { temp[i] += "," + headers[k]; } } } (str_isalpha() is just a function that applies isalpha() to every character in a string.) Now, the for-loop in this program doesn't execute, and I can't figure out why. Does anybody know?

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• Indices instead of pointers in STL containers?

  - by zvrba

  Due to specific requirements [*], I need a singly-linked list implementation that uses integer indices instead of pointers to link nodes. The indices are always interpreted with respect to a vector containing the list nodes. I thought I might achieve this by defining my own allocator, but looking into the gcc's implementation of , they explicitly use pointers for the link fields in the list nodes (i.e., they do not use the pointer type provided by the allocator): struct _List_node_base { _List_node_base* _M_next; ///< Self-explanatory _List_node_base* _M_prev; ///< Self-explanatory ... } (For this purpose, the allocator interface is also deficient in that it does not define a dereference function; "dereferencing" an integer index always needs a pointer to the underlying storage.) Do you know a library of STL-like data structures (i am mostly in need of singly- and doubly-linked list) that use indices (wrt. a base vector) instead of pointers to link nodes? [*] Saving space: the lists will contain many 32-bit integers. With two pointers per node (STL list is doubly-linked), the overhead is 200%, or 400% on 64-bit platform, not counting the overhead of the default allocator.

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• Providing less than operator for one element of a pair

  - by Koszalek Opalek

  What would be the most elegant way too fix the following code: #include <vector> #include <map> #include <set> using namespace std; typedef map< int, int > row_t; typedef vector< row_t > board_t; typedef row_t::iterator area_t; bool operator< ( area_t const& a, area_t const& b ) { return( a->first < b->first ); }; int main( int argc, char* argv[] ) { int row_num; area_t it; set< pair< int, area_t > > queue; queue.insert( make_pair( row_num, it ) ); // does not compile }; One way to fix it is moving the definition of less< to namespace std (I know, you are not supposed to do it.) namespace std { bool operator< ( area_t const& a, area_t const& b ) { return( a->first < b->first ); }; }; Another obvious solution is defining less than< for pair< int, area_t but I'd like to avoid that and be able to define the operator only for the one element of the pair where it is not defined.

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• using string to read file - XCode

  - by Fernando

  The following does not work and gives me a SIGABRT when I run in the debugger: std::ifstream inFile; inFile.open("/Users/fernandonewyork/inputText.txt"); cout << inFile << endl; vector<string> inText; if (inFile) { string s4; while (inFile>>s4) { inText.push_back(s4); } } inFile.close(); The following does: std::ifstream inFile; inFile.open("/Users/fernandonewyork/inputText.txt"); cout << inFile << endl; vector<string> inText; if (inFile) { string s4("This is no lnger an empty string"); while (inFile>>s4) { inText.push_back(s4); } } inFile.close(); I was under the impression I was able to simply use s4 without having to worry about any space considerations, or is something else happening here? This is the full error I get from the top code: malloc: * error for object 0x100010a20: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug Program received signal: “SIGABRT”.

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• Swt file dialog too much files selected?

  - by InsertNickHere

  Hi there, the swt file dialog will give me an empty result array if I select too much files (approx. 2500files). The listing shows you how I use this dialog. If i select too many sound files, the syso will show 0. Debugging tells me, that the files array is empty in this case. Is there any way to get this work? FileDialog fileDialog = new FileDialog(mainView.getShell(), SWT.MULTI); fileDialog.setText("Choose sound files"); fileDialog.setFilterExtensions(new String[] { new String("*.wav") }); Vector<String> result = new Vector<String>(); fileDialog.open(); String[] files = fileDialog.getFileNames(); for (int i = 0, n = files.length; i < n; i++) { if( !files[i].contains(".wav")) { System.out.println(files[i]); } StringBuffer stringBuffer = new StringBuffer(); stringBuffer.append(fileDialog.getFilterPath()); if (stringBuffer.charAt(stringBuffer.length() - 1) != File.separatorChar) { stringBuffer.append(File.separatorChar); } stringBuffer.append(files[i]); stringBuffer.append(""); String finalName = stringBuffer.toString(); if( !finalName.contains(".wav")) { System.out.println(finalName); } result.add(finalName); } System.out.println(result.size()) ;

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• Accept templated parameter of stl_container_type<string>::iterator

  - by Rodion Ingles

  I have a function where I have a container which holds strings (eg vector<string>, set<string>, list<string>) and, given a start iterator and an end iterator, go through the iterator range processing the strings. Currently the function is declared like this: template< typename ContainerIter> void ProcessStrings(ContainerIter begin, ContainerIter end); Now this will accept any type which conforms to the implicit interface of implementing operator*, prefix operator++ and whatever other calls are in the function body. What I really want to do is have a definition like the one below which explicitly restricts the amount of input (pseudocode warning): template< typename Container<string>::iterator> void ProcessStrings(Container<string>::iterator begin, Container<string>::iterator end); so that I can use it as such: vector<string> str_vec; list<string> str_list; set<SomeOtherClass> so_set; ProcessStrings(str_vec.begin(), str_vec.end()); // OK ProcessStrings(str_list.begin(), str_list.end()); //OK ProcessStrings(so_set.begin(), so_set.end()); // Error Essentially, what I am trying to do is restrict the function specification to make it obvious to a user of the function what it accepts and if the code fails to compile they get a message that they are using the wrong parameter types rather than something in the function body that XXX function could not be found for XXX class.

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