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  • What are function pointers good for ?

    - by gramm
    Hi, I have trouble seing the utility of the function pointers. I guess it may be useful in some case (it exists, after all), but I can't think of a case where it's better or unavoidable to use a function pointer. Could you give some example of good use of function pointers (in C or C++)? Many thanks :)

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  • Cocoa : How do I catch drag operations initiated from an IKBrowserView?

    - by bucketmouse
    So I've got an IKBrowserView all wired up and happily dragging my custom datatype (provided lazily via PasteboardItem) from one window to another, but now I'm interested in detecting when the user drops some data onto the trashcan. Cocoa's documentation says to check the return type of the drag operation itself, but how exactly do I do this with an IKBrowserView? Once I call imageBrowser:writeItemsAtIndexes:toPasteboard: I don't seem to get any notifications other than the request for the pasteboard contents, which doesn't provide a pointer to the drag operation that invoked it.

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  • How to create factories with attr_accesible?

    - by regedarek
    How to deal with factories and attr_accessible? My example: # model class SomeModel attr_accessible :name, full_name, other_name end #spec require 'spec_helper' describe "test" do it do create(:some_model, name: "test name", user: User.first) #factory end end #error ruby(17122,0x12a055000) malloc: *** error for object 0x8: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug I think the error is because user_id is not in attr_accesible atributes

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  • Communicate between separate MPI-Programs

    - by Fyg
    I have the following problem: Program 1 has a huge amount of data, say 10GB. The data in question consists of large integer- and double-arrays. Program 2 has 1..n MPI processes that use tiles of this data to compute results. How can I send the data from program 1 to the MPI Processes? Using File I/O is out of question. The compute node has sufficient RAM.

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  • How to access xmlParserCtxt structure from within xmlSAXHandler callbacks?

    - by Lux In Tenebris
    I'm parsing (X)HTML pages content with libxml using the following call: htmlDocPtr doc = htmlSAXParseDoc(content, NULL, &html_handler, NULL); But for debugging purposes I need to analyze some of the current node properties in the start/end element callbacks. I know that the fourth argument of htmlSAXParseDoc can be used to pass any user defined data to the callbacks, but I don't have a pointer to xmlParserCtxt.

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  • Unable to free const pointers in C

    - by lego69
    How can I free a const char*? I allocated new memory using malloc, and when I'm trying to free it I always receive the error "incompatible pointer type" The code that causes this is something like: char* name="Arnold"; const char* str=(const char*)malloc(strlen(name)+1); free(str); // error here

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  • Is there a way to prevent a string of letters with no spaces from overflowing out of its correspondi

    - by Scarface
    The question is pretty straight forward, I have tried using a span with rules set to clear:both; and display:block;, at the bottom of each list entry where the text is being inserted in with no luck. I am not really sure what to do on this. I don't expect to many entries with long consecutive letter strings but for example if someone does lolololololol or ahaahahahhhhhhhhhhhhaaaaaaaa for like 100 letters, it will overflow. If anyone can give me a pointer I would really appreciate it.

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  • text from a file turned into a variable?

    - by b3y4z1d
    If I made a program that stores strings on a text file using the "list"-function(#include ), and then I want to copy all of the text from that file and call it something(so I can tell the program to type in all of the text I copied somewhere by using that one variable to refer to the text), do I use a string,double,int or what do I declare that chunk of text as? I'm making the program using c++ in a simple console application.

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  • JRadio Menu buttons - JAVA

    - by user337465
    I have a relatively easy question. I have to create a java GUI to do math based calculations. I have to have a menu item that will double the variable that I am doing calculations with. For example variable = 1 if radio button = selected{ variable = variable * 2 } So, how would I achieve the if statement there? thankyou

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  • Fundamental types

    - by smerlin
    I always thought the following types are "fundamental types", so i thought my anwser to this question would be correct, but surprisingly it got downvoted... Searching the web, i found this. So, IBM says aswell those types are fundamental types.. Well how do you interpret the Standard, are following types (and similar types), "fundamental types" according to the c++ standard ? unsigned int signed char long double long long long long int unsigned long long int

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  • SDL_GL_SwapBuffers Segfault

    - by RyanG
    I'm getting a segfault that GDB says is coming from SDL_GL_SwapBuffers. However, I can't imagine why. The SDL documentation mentions no specific pre-conditions for calling swapBuffers except that double buffering be allowed. Is this an option I have to turn on while initializing OpenGL or is this a hardware capability thing? My code: http://pastie.org/859721 (Ignore the unused variables, strange comments and other things. I haven't prettied this up at all. :P)

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  • C++ segmentation error when first parameter is null in comparison operator overload

    - by user1774515
    I am writing a class called Word, that handles a c string and overloads the <, , <=, = operators. word.h: friend bool operator<(const Word &a, const Word &b); word.cc: bool operator<(const Word &a, const Word &b) { if(a == NULL && b == NULL) return false; if(a == NULL) return true; if(b == NULL) return false; return a.wd < b.wd; //wd is a valid c string } main: char* temp = NULL; //EDIT: i was mistaken, temp is a char pointer Word a("blah"); //a.wd = [b,l,a,h] cout << (temp<a); i get a segmentation error before the first line of the operator< method after the last line in the main. I can correct the problem by writing cout << (a>temp); where the operator> is similarly defined and i get no errors. but my assignment requires (temp < a) to work so this is where i ask for help. EDIT: i made a mistake the first time and i said temp was of type Word, but it is actually of type char*. so i assume that the compiler converts temp to a Word using one of my constructors. i dont know which one it would use and why this would work since the first parameter is not Word. here is the constructor i think is being used to make the Word using temp: Word::Word(char* c, char* delimeters=NULL) { char *temporary = "\0"; if(c == NULL) c = temporary; check(stoppers!=NULL, "(Word(char*,char*))NULL pointer"); //exits the program if the expression is false if(strlen(c) == 0) size = DEFAULT_SIZE; //10 else size = strlen(c) + 1 + DEFAULT_SIZE; wd = new char[size]; check(wd!=NULL, "Word(char*,char*))heap overflow"); delimiters = new char[strlen(stoppers) + 1]; //EDIT: changed to [] check(delimiters!=NULL,"Word(char*,char*))heap overflow"); strcpy(wd,c); strcpy(delimiters,stoppers); count = strlen(wd); } wd is of type char* thanks for looking at this big question and trying to help. let me know if you need more code to look at

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  • JNA array structure

    - by Burny
    I want to use a dll (IEC driver) in Java, for that I am using JNA. The problem in pseudo code: start the server allocate new memory for an array (JNA) client connect writing values from an array to the memory sending this array to the client client disconnect new client connect allocate new memory for an array (JNA) - JVM crash (EXCEPTION_ACCESS_VIOLATION) The JVM crash not by primitve data types and if the values will not writing from the array to the memory. the code in c: struct DataAttributeData CrvPtsArrayDAData = {0}; CrvPtsArrayDAData.ucType = DATATYPE_ARRAY; CrvPtsArrayDAData.pvData = XYValDAData; XYValDAData[0].ucType = FLOAT; XYValDAData[0].uiBitLength = sizeof(Float32)*8; XYValDAData[0].pvData = &(inUpdateValue.xVal); XYValDAData[1].ucType = FLOAT; XYValDAData[1].uiBitLength = sizeof(Float32)*8; XYValDAData[1].pvData = &(inUpdateValue.yVal); Send(&CrvPtsArrayDAData, 1); the code in Java: DataAttributeData[] data_array = (DataAttributeData[]) new DataAttributeData() .toArray(d.bitLength); for (DataAttributeData d_temp : data_array) { d_temp.data = new Memory(size / 8); d_temp.type = type_iec; d_temp.bitLength = size; d_temp.write(); } d.data = data_array[0].getPointer(); And then writing values whith this code: for (int i = 0; i < arraySize; i++) { DataAttributeData dataAttr = new DataAttributeData(d.data.share(i * d.size())); dataAttr.read(); dataAttr.data.setFloat(0, f[i]); dataAttr.write(); } the struct in c: struct DataAttributeData{ unsigned char ucType; int iArrayIndex; unsigned int uiBitLength; void * pvData;}; the struct in java: public static class DataAttributeData extends Structure { public DataAttributeData(Pointer p) { // TODO Auto-generated constructor stub super(p); } public DataAttributeData() { // TODO Auto-generated constructor stub super(); } public byte type; public int iArrayIndex; public int bitLength; public Pointer data; @Override protected List<String> getFieldOrder() { // TODO Auto-generated method stub return Arrays.asList(new String[] { "type", "iArrayIndex", "bitLength", "data" }); } } Can anybody help me?

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  • Fixing Floating Point Error

    - by HannesNZ
    I have some code that gets the leading value (non-zero) of a Double using normal math instead of String Math... For Example: 0.020 would return 2 3.12 would return 3 1000 should return 1 The code I have at the moment is: LeadingValue := Trunc(ResultValue * Power(10, -(Floor(Log10(ResultValue))))) However when ResultValue is 1000 then LeadingValue ends up as 0. What can I do to fix this problem I'm assuming is being caused by floating point errors? Thanks.

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  • How to handle when SSRS does not automatically update fields based on database query?

    - by badpanda
    So I am trying to change the number of fields in my dataset in SSRS and the refresh button is not picking up the added field from the SQL server. The query is definitely returning the correct data, as I have double checked in the server engine itself. Also, I have tried manually adding the field using the SSRS menu, but as soon as I execute it disappears. Any suggestions or similar experiences?

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  • looking for a javascript engine

    - by c0f33.alex
    i'm looking for a js engine to that I can (easily) expose C/C++ functions, classes etc. The API should allow changing exposed values from within C++ (by storing some kind of pointer or reference to an object inside js or so...). I've considered using google's v8 but I'm new to it and don't know whether it will satisfy my requirements. Can someone tell me whether I should stick to v8 or try something else?

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  • C++ memcpy problem :(

    - by Simon
    Hey all :) I have a problem my src pointer of memcpy is pointing wrong. unsigned char* lpBuffer is a buffer that contains my bytes, i checked with olly. The code: IMAGE_DOS_HEADER iDOSh; memcpy(&iDOSh,lpBuffer,sizeof(iDOSh)); The problem is that lpBuffer points wrong, output from debugger is dest = 002859E8 RIGHT src = 000001D8 FALSE src is pointing invalid :( i have no idea why Thanks for reading

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