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  • Is there a way to use template specialization to separate new from new[]?

    - by Marlon
    I have an auto pointer class and in the constructor I am passing in a pointer. I want to be able to separate new from new[] in the constructor so that I can properly call delete or delete[] in the destructor. Can this be done through template specialization? I don't want to have to pass in a boolean in the constructor. template <typename T> class MyAutoPtr { public: MyAutoPtr(T* aPtr); }; // in use: MyAutoPtr<int> ptr(new int); MyAutoPtr<int> ptr2(new int[10]);

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  • Multiplying complex with constant in C++

    - by Atilla Filiz
    The following code fails to compile #include <iostream> #include <cmath> #include <complex> using namespace std; int main(void) { const double b=3; complex <double> i(0, 1), comp; comp = b*i; comp=3*i; return 0; } with error: no match for ‘operator*’ in ‘3 * i’ What is wrong here, why cannot I multiply with immediate constants?

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  • Why wont my while loop wont take new input (c++)

    - by Van
    I've written a program to get a string input from a user and parse it into tokens and move a robot according to the input. My problem is trying to issue more than one command. The code looks like: void Navigator::manualDrive() { const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; while(true) { Navigator::parseInstruction(uinput); } } /* parseInstruction(char *c) -- parses cstring instructions received * and moves robot accordingly */ void Navigator::parseInstruction(char * c) { const int bufSize = 42; char uinput[bufSize]; char delim[] = " "; char *token; cout << "Enter your directions below: \n"; cin.ignore(); cin.getline (uinput, bufSize); token=strtok(uinput, delim); if(strcmp("forward", token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); Navigator::travel(inches); } if(strcmp("back",token) == 0) { int inches; token = strtok(NULL, delim); inches = atoi (token); double value = fabs(0.0735 * fabs(inches) - 0.0550); myRobot.backward(1/*speed*/, value/*time*/); } if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("left",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.0041 * degrees - 0.0523); myRobot.turnLeft(1/*speed*/, value/*time*/); } } if(strcmp("turn",token) == 0) { int degrees; token = strtok(NULL, delim); if(strcmp("right",token) == 0) { token = strtok(uinput, delim); degrees = atoi (token); double value = fabs(0.0041 * degrees - 0.0523); myRobot.turnRight(1/*speed*/, value/*time*/); } } if(strcmp("stop",token) == 0) { myRobot.motors(0,0); } } In the function manualDrive I have a while loop calling the function parseInstruction infinitely. The program outputs "Enter your directions below: " When I give the program instructions it executes them, and then it outputs "enter your directions below: " again and when I input my directions again it does not execute them and outputs "Enter your directions below: " instead. I'm sure this is a very simple fix I'm just very new to c++. So if you could please help me out and tell me why the program only takes the first set of directions. thanks

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  • Can i have a negative value as constant expression in Scala?

    - by Klinke
    I have an Java-Annotation that return a double value: @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.FIELD) public @interface DoubleValue { double value(); } When i try to attach the annotation to a field in a scala class and the value is negativ like here: class Test { @DoubleValue(-0.05) var a = _ } i get an compiler error with the message: "annotation argument needs to be a constant; found: 0.05.unary_-". I understood that i need a numerical literal and i looked into the Scala Language Specification and it seems, that the - sign is only used for the exponent but not for the mantissa. Does someone has an idea how i can have a negative value as runtime information using annotations? Thanks, Klinke

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  • Silencing GCC warnings when using an "Uncopyable" class

    - by Kazade
    I have several classes that I don't want to be copyable, some of these classes have pointer data members. To make these classes uncopyable I privately inherit the following class template: template <class T> class Uncopyable { protected: Uncopyable() {} virtual ~Uncopyable() {} private: Uncopyable(const Uncopyable &); T & operator=(const T&); }; Which I used like so: class Entity : private Uncopyable<Entity> { } This works fine, however when I compile with -Weffc++ I still get the following warning: class Entity has pointer data members but does not override Entity(const Entity&) or operator=(const Entity&) Why is it still giving me this warning?

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  • Cuda program results are always zero in HW, correct in EMU??

    - by Orion Nebula
    Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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  • business object and codelist

    - by feiroox
    Hi How to design a business object? I have a library which returns me an Object which have ten lists of other different objects. I need to store it into database all. List of objects are often like: class Item { private int id; private String name; private double point; } But the name is often the same. Like basic title of the product or code. Containing from 3 characters up to 70characters. Should I make conversion for every Object to: (or something similar) class ConvertedItem { private int id; private int code; private double point; } And have a separated table of codes ( I guess around 60). Or do not bother with duplicated stuff? It's not mission critical app. What would you do in my case? thanks in advance

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  • Operator() as a subscript (C++)

    - by Ivan Gromov
    I use operator() as a subscript operator this way: double CVector::operator() (int i) const { if (i >= 0 && i < this->size) return this->data[i]; else return 0; } double& CVector::operator() (int i) { return (this->data[i]); } It works when I get values, but I get an error when I try to write assign a value using a(i) = 1; UPD: Error text: Unhandled exception at 0x651cf54a (msvcr100d.dll) in CG.exe: 0xC0000005: Access violation reading location 0xccccccc0.

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  • Speed up multiple JDBC SQL querys?

    - by paddydub
    I'm working on a shortest path a* algorithm in java with a mysql db. I'm executing the following SQL Query approx 300 times in the program to find route connections from a database of 10,000 bus connections. It takes approx 6-7 seconds to execute the query 300 times. Any suggestions on how I can speed this up or any ideas on a different method i can use ? Thanks ResultSet rs = stmt.executeQuery("select * from connections" + " where Connections.From_Station_stopID ="+StopID+";"); while (rs.next()) { int id = rs.getInt("To_Station_id"); String routeID = rs.getString("To_Station_routeID"); Double lat = rs.getDouble("To_Station_lat"); Double lng = rs.getDouble("To_Station_lng"); int time = rs.getInt("Time"); }

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  • strange results with /fp:fast

    - by martinus
    We have some code that looks like this: inline int calc_something(double x) { if (x > 0.0) { // do something return 1; } else { // do something else return 0; } } Unfortunately, when using the flag /fp:fast, we get calc_something(0)==1 so we are clearly taking the wrong code path. This only happens when we use the method at multiple points in our code with different parameters, so I think there is some fishy optimization going on here from the compiler (Microsoft Visual Studio 2008, SP1). Also, the above problem goes away when we change the interface to inline int calc_something(const double& x) { But I have no idea why this fixes the strange behaviour. Can anyone explane this behaviour? If I cannot understand what's going on we will have to remove the /fp:fastswitch, but this would make our application quite a bit slower.

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  • Ruby on Rails: how to render a string as HTML?

    - by Tim
    I have @str = "<b>Hi</b>" and in my erb view: <%= @str > What will display on the page is: <b>Hi</b> when what I really want is Hi. What's the ruby way to "interpret" a string as HTML markup? Edit: the case where @str = "<span class=\"classname\">hello</span>" If in my view I do <%raw @str %> The HTML source code is <span class=\"classname\">hello</span where what I really want is <span class="classname">hello</span> (without the backslashes that were escaping the double quotes). What's the best way to "unescape" those double quotes?

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  • How to launch a mac application without a terminal window.

    - by KPexEA
    I've written an open-source c++ application and it works fine on Windows and Linux, I finally got a Mac Mini (with 10.5.8) so I've just been testing the Mac version. My application works fine when running it from inside a terminal window and typing ./appname , but if instead I double click on it from the finder, then it opens a termnial window first and then runs my app but it doesn't seem to set the working directory to the correct location so my app dies. How do I make my app so when it launches by being double clicked on it doesn't open a terminal window first and how can I have the current directory set to the apps location automatically?

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  • "SQLSTATE[23000]: Integrity constraint violation" in Doctrine

    - by rags
    Hi, i do get an Integrity constraint violation for Doctrine though i really can't see why. Schema.yml User: columns: id: type: integer primary: true autoincrement: true username: type: varchar(64) notnull: true email: type: varchar(128) notnull: true password: type: varchar(128) notnull: true relations: Websites: class: Website local: id foreign: owner type: many foreignType: one onDelete: CASCADE Website: columns: id: type: integer primary: true autoincrement: true active: type: bool owner: type: integer notnull: true plz: type: integer notnull: true longitude: type: double(10,6) notnull: true latitude: type: double(10,6) notnull: true relations: Owner: type: one foreignType: many class: User local: owner foreign: id And here's my data Fixtures (data.yml) Model_User: User_1: username: as email: as****.com password: ***** Model_Website: Website_1: active: true plz: 34222 latitude: 13.12 longitude: 3.56 Owner: User_1

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  • how to start stop tomcat server using CMD?

    - by ali
    i set the path for the tomcat and set all variables like 1.JAVA_HOME=C:\Program Files (x86)\Java\jdk1.6.0_22 2.CATALINA_HOME=G:\springwork\server\apache-tomcat-6.0.29 3.CLASSPATH=G:\springwork\server\apache-tomcat-6.0.29\lib\servlet-api.jar;G:\springwork\server\apache-tomcat-6.0.29\lib\jsp-api.jar;.; when i go to bin folder and double click on startup.bat then my tomcat start and when i double click on shutdown.bat tomcat is stop. But I want using CMD start and stop the tomcat. And in any folder i write command startup.bat the server will start and when i write the server will stop...... Thanks in advace..........

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  • Primary reasons why programming language runtimes use stacks?

    - by manuel aldana
    Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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  • For-Each and Pointers in Java

    - by John
    Ok, so I'm tyring to iterate through an ArrayList and remove a specefic element. However, I am having some trouble using the For-Each like structure. When I run the following code: ArrayList<String> arr = new ArrayList<String>(); //... fill with some values (doesn't really matter) for(String t : arr) { t = " some other value "; //hoping this would change the actual array } for(String t : arr) { System.out.println(t); //however, I still get the same array here } My question in, how can I make 't' a pointer to 'arr' so that I am able to change the values in a for-each loop? I know I could loop through the ArrayList using a different structure, but this one looks so clean and readable, it would just be nice to be able to make 't' a pointer. All comments are appreciated! Even if you say I should just suck it up and use a different construct.

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  • Code crashing compiler: main() returning a struct instead of an int

    - by AndrejaKo
    Hi! I'm experimenting with a piece of C code. Can anyone tell me why is VC 9.0 with SP1 crashing for me? Oh, and the code is meant to be an example used in a discussion why something like void main (void) is evil. struct foo { int i; double d; } main (double argc, struct foo argv) { struct foo a; a.d=0; a.i=0; return a.i; } If I put return a; compiler doesn't crash.

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • How do I implement this public accesible enum

    - by Psytronic
    Hey guys, I'm trying to access my class's private enum. But I don't understand the difference needed to get it working compared to other members; If this works: private double dblDbl = 2; //misc code public double getDblDbl{ get{ return dblDbl; } } Why can I not do it with enum? private enum myEnum{ Alpha, Beta}; //misc code public Enum getMyEnum{ get{ return myEnum; } } //throws "Window1.myEnum" is a "type" but is used like a variable

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  • grdb not working variables

    - by stupid_idiot
    hi, i know this is kinda retarded but I just can't figure it out. I'm debugging this: xor eax,eax mov ah,[var1] mov al,[var2] call addition stop: jmp stop var1: db 5 var2: db 6 addition: add ah,al ret the numbers that I find on addresses var1 and var2 are 0x0E and 0x07. I know it's not segmented, but that ain't reason for it to do such escapades, because the addition call works just fine. Could you please explain to me where is my mistake? I see the problem, dunno how to fix it yet though. The thing is, for some reason the instruction pointer starts at 0x100 and all the segment registers at 0x1628. To address the instruction the used combination is i guess [cs:ip] (one of the segment registers and the instruction pointer for sure). The offset to var1 is 0x10 (probably because from the begining of the code it's the 0x10th byte in order), i tried to examine the memory and what i got was: 1628:100 8 bytes 1628:108 8 bytes 1628:110 <- wtf? (assume another 8 bytes) 1628:118 ... whatever tricks are there in the memory [cs:var1] points somewhere else than in my code, which is probably where the label .data would usually address ds.... probably.. i don't know what is supposed to be at 1628:10 ok, i found out what caused the assness and wasted me whole fuckin day. the behaviour described above is just correct, the code is fully functional. what i didn't know is that grdb debugger for some reason sets the begining address to 0x100... the sollution is to insert the directive ORG 0x100 on the first line and that's the whole thing. the code was working because instruction pointer has the right address to first instruction and goes one by one, but your assembler doesn't know what effective address will be your program stored at so it pretty much remains relative to first line of the code which means all the variables (if not using label for data section) will remain pointing as if it started at 0x0. which of course wouldn't work with DOS. and grdb apparently emulates some DOS features... sry for the language, thx everyone for effort, hope this will spare someone's time if having the same problem... heheh.. at least now i know the reason why to use .data section :))))

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  • Matlab: Randomize and Split

    - by Null-Hypothesis
    I have following data matrix in Matlab, I am trying to actually split this into multiple segments by passing a variable to a matlab function. But before splitting I would like to shuffle the matrix. The size of my matrix is 150X4 s.data 5.1000 3.5000 1.4000 0.2000 4.9000 3.0000 1.4000 0.2000 4.7000 3.2000 1.3000 0.2000 4.6000 3.1000 1.5000 0.2000 5.0000 3.6000 1.4000 0.2000 .. s = data: [150x4 double] labels: [150x1 double] Coming from R environment I find MatLab is very strange. Initially I thought the columns in matrix has a relationshop like in a R dataframe but thats wrong in my assumption.

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  • Unmanaged C++ instantiation question

    - by Jim Jones
    Want to verify that my understanding of how this works. Have an unmanaged C++ Class with one public instance variable: char* character_encoding; and whose only constructor is defined as: TF_StringList(const char* encoding = "cp_1252"); when I use this class in either managed or unmanaged C++, the first thing I do is declare a pointer to an object of this class: const TF_StringList * categories; Then later I instantiate it: categories = new TF_StringList(); this gives me a pointer to an object of type TF_StringList whose variable character_encoding is set to "cp_1252"; So, is all that logic valid? Jim

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  • Multiple word Auttosuggest using Lucene.Net

    - by eric
    I am currently working on an search application which uses Lucene.Net to index the data from the database to Index file. I have a product catalog which has Name, short and long description, sku and other fields. The data is stored in Index using StandardAnalyzer. I am trying to add auto suggestion for a text field and using TermEnum to get all the keyword terms and its score from the Index. But the terms returned are of single term. For example, if I type for co, the suggestion returned are costume, count, collection, cowboy, combination etc. But I want the suggestion to return phrases. For exmaple, if I search for co, the suggestions should be cowboy costume, costume for adults, combination locks etc. The following is the code used to get the suggestions: public string[] GetKeywords(string strSearchExp) { IndexReader rd = IndexReader.Open(mIndexLoc); TermEnum tenum = rd.Terms(new Term("Name", strSearchExp)); string[] strResult = new string[10]; int i = 0; Dictionary<string, double> KeywordList = new Dictionary<string, double>(); do { //terms = tenum.Term(); if (tenum.Term() != null) { //strResult[i] = terms.text.ToString(); KeywordList.Add(tenum.Term().text.ToString(), tenum.DocFreq()); } } while (tenum.Next() && tenum.Term().text.StartsWith(strSearchExp) && tenum.Term().text.Length > 1); var sortedDict = (from entry in KeywordList orderby entry.Value descending select entry); foreach (KeyValuePair<string, double> data in sortedDict) { if (data.Key.Length > 1) { strResult[i] = data.Key; i++; } if (i >= 10) //Exit the for Loop if the count exceeds 10 break; } tenum.Close(); rd.Close(); return strResult; } Can anyone please give me directions to achive this? Thanks for looking into this.

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  • Android quotes within an sql query string

    - by miannelle
    I want to perform a query like the following: uvalue = EditText( some user value ); p_query = "select * from mytable where name_field = '" + uvalue + "'" ; mDb.rawQuery( p_query, null ); if the user enters a single quote in their input it crashes. If you change it to: p_query = "select * from mytable where name_field = \"" + uvalue + "\"" ; it crashes if the user enters a double quote in their input. and of course they could always enter both single and double quotes.

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  • Linq query: append column to query results

    - by jrubengb
    I am trying to figure out how to append a column to Linq query results based on the max value of the query. Essentially, I want to create an EnumerableRowCollection of DataRows that would include a max value record with the same value for each record. So if i have a hundred records returned through the query, I want to next calculate the max value of one of the fields, then append that max value to the original query table: DataTable dt = new DataTable(); dt = myDataSet.myDataTable; EnumerableRowCollection<DataRow> qrySelectRecords = (from d in dt.AsEnumerable() where d.Field<DateTime>("readingDate") >= startDate && g.Field<DateTime>("readingDate") <= endDate select d); Here's where I need help: double maxValue = qrySelectRecords.Field<double>("field1").Max(); foreach (DataRow dr in qrySelectRecords) { qrySelectRecords.Column.Append(maxValue) }

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