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  • C++: get const or non-const reference type from trait

    - by maciekp
    I am writing a functor F which takes function of type void (*func)(T) and func's argument arg. Then functor F calls func with arg. I would like F not to copy arg, just to pass it as reference. But then I cannot simply write "void F(void (*func)(T), T&)" because T could be a reference. So I am trying to write a trait, which allows to get proper reference type of T: T -> T& T& -> T& const T -> const T& const T& -> const T& I come up with something like this: template<typename T> struct type_op { typedef T& valid_ref_type; }; template<typename T> struct type_op<T&> { typedef typename type_op<T>::valid_ref_type valid_ref_type; }; template<typename T> struct type_op<const T> { typedef const T& valid_ref_type; }; template<typename T> struct type_op<const T&> { typedef const T& valid_ref_type; }; Which doesn't work for example for void a(int x) { std::cout << x << std::endl; } F(&a, 7); Giving error: invalid initialization of non-const reference of type ‘int&’ from a temporary of type ‘int’ in passing argument 2 of ‘void f(void (*)(T), typename type_op::valid_ref_type) [with T = int]’ How to get this trait to work?

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  • Change HttpContext.Request.InputStream

    - by user320478
    I am getting lot of errors for HttpRequestValidationException in my event log. Is it possible to HTMLEncode all the inputs from override of ProcessRequest on web page. I have tried this but it gives context.Request.InputStream.CanWrite == false always. Is there any way to HTMLEncode all the feilds when request is made? public override void ProcessRequest(HttpContext context) { if (context.Request.InputStream.CanRead) { IEnumerator en = HttpContext.Current.Request.Form.GetEnumerator(); while (en.MoveNext()) { //Response.Write(Server.HtmlEncode(en.Current + " = " + //HttpContext.Current.Request.Form[(string)en.Current])); } long nLen = context.Request.InputStream.Length; if (nLen > 0) { string strInputStream = string.Empty; context.Request.InputStream.Position = 0; byte[] bytes = new byte[nLen]; context.Request.InputStream.Read(bytes, 0, Convert.ToInt32(nLen)); strInputStream = Encoding.Default.GetString(bytes); if (!string.IsNullOrEmpty(strInputStream)) { List<string> stream = strInputStream.Split('&').ToList<string>(); Dictionary<int, string> data = new Dictionary<int, string>(); if (stream != null && stream.Count > 0) { int index = 0; foreach (string str in stream) { if (str.Length > 3 && str.Substring(0, 3) == "txt") { string textBoxData = str; string temp = Server.HtmlEncode(str); //stream[index] = temp; data.Add(index, temp); index++; } } if (data.Count > 0) { List<string> streamNew = stream; foreach (KeyValuePair<int, string> kvp in data) { streamNew[kvp.Key] = kvp.Value; } string newStream = string.Join("", streamNew.ToArray()); byte[] bytesNew = Encoding.Default.GetBytes(newStream); if (context.Request.InputStream.CanWrite) { context.Request.InputStream.Flush(); context.Request.InputStream.Position = 0; context.Request.InputStream.Write(bytesNew, 0, bytesNew.Length); //Request.InputStream.Close(); //Request.InputStream.Dispose(); } } } } } } base.ProcessRequest(context); }

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  • what should be the return type of the hashCode()

    - by subhashis
    The signature of the hashCode() method is public int hashCode(){ return x; } in this case x must be an int(primitive) but plz can anyone explain it to me that the number which the hashCode() returns must be a prime number, even number...etc or there is no specification ? the reason behind i am asking this question is i have seen it in different ids the auto generated code always returns a prime number, so i need to know why? thanks in advance

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  • KeyNotFound Exception in Dictionary(of T)

    - by C Patton
    I'm about ready to bang my head against the wall I have a class called Map which has a dictionary called tiles. class Map { public Dictionary<Location, Tile> tiles = new Dictionary<Location, Tile>(); public Size mapSize; public Map(Size size) { this.mapSize = size; } //etc... I fill this dictionary temporarily to test some things.. public void FillTemp(Dictionary<int, Item> itemInfo) { Random r = new Random(); for(int i =0; i < mapSize.Width; i++) { for(int j=0; j<mapSize.Height; j++) { Location temp = new Location(i, j, 0); int rint = r.Next(0, (itemInfo.Count - 1)); Tile t = new Tile(new Item(rint, rint)); tiles[temp] = t; } } } and in my main program code Map m = new Map(10, 10); m.FillTemp(iInfo); Tile t = m.GetTile(new Location(2, 2, 0)); //The problem line now, if I add a breakpoint in my code, I can clearly see that my instance (m) of the map class is filled with pairs via the function above, but when I try to access a value with the GetTile function: public Tile GetTile(Location location) { if(this.tiles.ContainsKey(location)) { return this.tiles[location]; } else { return null; } } it ALWAYS returns null. Again, if I view inside the Map object and find the Location key where x=2,y=2,z=0 , I clearly see the value being a Tile that FillTemp generated.. Why is it doing this? I've had no problems with a Dictionary such as this so far. I have no idea why it's returning null. and again, when debugging, I can CLEARLY see that the Map instance contains the Location key it says it does not... very frustrating. Any clues? Need any more info? Help would be greatly appreciated :)

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  • How to Auto-Increment Non-Primary Key? - SQL Server

    - by user311509
    CREATE TABLE SupplierQuote ( supplierQuoteID int identity (3504,2) CONSTRAINT supquoteid_pk PRIMARY KEY, PONumber int identity (9553,20) NOT NULL . . . CONSTRAINT ponumber_uq UNIQUE(PONumber) ); The above ddl produces an error: Msg 2744, Level 16, State 2, Line 1 Multiple identity columns specified for table 'SupplierQuote'. Only one identity column per table is allowed. How can i solve it? I want PONumber to be auto-incremented.

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  • Why is the Objective-C Boolean data type defined as a signed char?

    - by EddieCatflap
    Something that has piqued my interest is Objective-C's BOOL type definition. Why is it defined as a signed char (which could cause unexpected behaviour if a value greater than 1 byte in length is assigned to it) rather than as an int, as C does (much less margin for error: a zero value is false, a non-zero value is true)? The only reason I can think of is the Objective-C designers micro-optimising storage because the char will use less memory than the int. Please can someone enlighten me?

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  • socket problem in java

    - by stefan89
    I have two classes X and Y, like this: class X implements Serializable { int val1; Y val2; } class Y implements Serializable { int val; } I want to transmit an object of type X from a client to server but i can't because the class X has a field of type Y. I replace the field of type Y with a field of type X in class X and it works.

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  • [Android] Show default selection color for custom listview

    - by Diego
    Hello, I have a listview with a custom BaseAdapter. Each row of the listview has a TextView and a CheckBox. The problem is when I click (or touch) any row, the textview foreground becomes gray, instead of the default behavior (background - green, textview foreground - white). Here is the code: row.xml: <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" style="@style/layout"> <TextView android:id="@+id/main_lv_item_textView" style="@style/textViewBig" android:layout_alignParentLeft="true"/> <CheckBox android:id="@+id/main_lv_item_checkBox" style="@style/checkBox" android:layout_width="wrap_content" android:layout_alignParentRight="true"/> </RelativeLayout> Custom Adapter: public class CustomAdapter extends BaseAdapter { private List<Profile> profiles; private LayoutInflater inflater; private TextView tvName; private CheckBox cbEnabled; public CustomAdapter(List<Profile> profiles) { this.profiles = profiles; inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } public int getCount() { return profiles.size(); } public Object getItem(int position) { return profiles.get(position); } public long getItemId(int position) { return position; } public View getView(final int position, View convertView, ViewGroup parent) { View row = inflater.inflate(R.layout.main_lv_item, null); final Profile profile = profiles.get(position); tvName = (TextView) row.findViewById(R.id.main_lv_item_textView); registerForContextMenu(tvName); cbEnabled = (CheckBox) row.findViewById(R.id.main_lv_item_checkBox); tvName.setText(profile.getName()); if (profile.isEnabled()) { cbEnabled.setChecked(true); } tvName.setOnClickListener(new OnClickListener() { public void onClick(View v) { Bundle bundle = new Bundle(); bundle.putString(PROFILE_NAME_KEY, profile.getName()); Intent intent = new Intent(context, GuiProfile.class); intent.putExtras(bundle); startActivity(intent); } }); tvName.setOnLongClickListener(new OnLongClickListener() { public boolean onLongClick(View v) { selectedProfileName = ((TextView) v).getText().toString(); return false; } }); cbEnabled.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { if (!profile.isEnabled()) { for (Profile profile : profiles) { if (profile.isEnabled()) { profile.setEnabled(false); Database.getInstance().storeProfile(profile); } } } profile.setEnabled(isChecked); Database.getInstance().storeProfile(profile); updateListView(); } }); return row; } } Any help would be appreciated.

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  • Selecting by ID in Castle ActiveRecord

    - by ripper234
    How can I write a criteria to return all Orders that belong to a specific User? public class User { [PrimaryKey] public virtual int Id { get; set; } } public class Order { [PrimaryKey] public virtual int Id { get; set; } [BelongsTo("UserId")] public virtual User User { get; set; } } return ActiveRecordMediator<Order>.FindAll( // What criteria should I write here ? );

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  • Multi-threaded random_r is slower than single threaded version.

    - by Nixuz
    The following program is essentially the same the one described here. When I run and compile the program using two threads (NTHREADS == 2), I get the following run times: real 0m14.120s user 0m25.570s sys 0m0.050s When it is run with just one thread (NTHREADS == 1), I get run times significantly better even though it is only using one core. real 0m4.705s user 0m4.660s sys 0m0.010s My system is dual core, and I know random_r is thread safe and I am pretty sure it is non-blocking. When the same program is run without random_r and a calculation of cosines and sines is used as a replacement, the dual-threaded version runs in about 1/2 the time as expected. #include <pthread.h> #include <stdlib.h> #include <stdio.h> #define NTHREADS 2 #define PRNG_BUFSZ 8 #define ITERATIONS 1000000000 void* thread_run(void* arg) { int r1, i, totalIterations = ITERATIONS / NTHREADS; for (i = 0; i < totalIterations; i++){ random_r((struct random_data*)arg, &r1); } printf("%i\n", r1); } int main(int argc, char** argv) { struct random_data* rand_states = (struct random_data*)calloc(NTHREADS, sizeof(struct random_data)); char* rand_statebufs = (char*)calloc(NTHREADS, PRNG_BUFSZ); pthread_t* thread_ids; int t = 0; thread_ids = (pthread_t*)calloc(NTHREADS, sizeof(pthread_t)); /* create threads */ for (t = 0; t < NTHREADS; t++) { initstate_r(random(), &rand_statebufs[t], PRNG_BUFSZ, &rand_states[t]); pthread_create(&thread_ids[t], NULL, &thread_run, &rand_states[t]); } for (t = 0; t < NTHREADS; t++) { pthread_join(thread_ids[t], NULL); } free(thread_ids); free(rand_states); free(rand_statebufs); } I am confused why when generating random numbers the two threaded version performs much worse than the single threaded version, considering random_r is meant to be used in multi-threaded applications.

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  • MySQL table data question?

    - by mySQL
    How should my Mysql table data look like for a single checkbox that checks and see if the user has said yes if its clicked or no if its not? Here is the checkbox. <input type="checkbox" name="yes" id="yes" value="yes" /> I was wondering how would I add it to the following table. CREATE TABLE IF NOT EXISTS `vote` ( `counter` int(8) NOT NULL default '0', `value` int(8) NOT NULL default '0' ) ENGINE=MyISAM DEFAULT CHARSET=latin1;

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  • C++ delete[] operator

    - by Betamoo
    Is this the right way to use delete[] operator? int* a=new int[size]; delete[] a; If yes, Who (compiler or GC or whoever) will determine the size of the newly created array? and where will it store the array size? Thanks

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  • changing a table to array

    - by LIX
    I have a temp table which I fill and clear it in a loop in my code. becouse of using database, it takes musch time. I want to change it to an array to run my app quicker. here is my table columns: ID ( int) , Type (string ), Amount (int) may anyone help me?

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  • C instruction address

    - by aaa
    hello. Disclaimer, I not do anything in particular with regards this question, just curious. Is it possible to take address of instruction or block in C? in essence, is there jump equivalent in C? for example: void function() { int k; { // is a possible to go to this address from arbitrary point in code? int i, j; k += j+i; } } thank you

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  • C++: Pass array created in the function call line

    - by Jarx
    How can I achieve a result like somebody would expect it according to the following code example: // assuming: void myFunction( int* arr ); myFunction( [ 123, 456, 789 ] ); // as syntactical sugar for... int values[] = { 123, 456, 789 }; myFunction( values ); The syntax I thought would work spit out a compile error. How can I define an argument array directly in the line where the function is called?

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  • passing an array struture as an array

    - by Matias
    I'm having trouble passing a struture array as a parameter of a funtion struct Estructure{ int a; intb; }; and a funtion Begining(Estructure &s1[]) { //modifi the estructure s1 }; and the main would be something like this int main() { Estructure m[200]; Begining(m); }; is this valid?

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  • Problem with pointers and getstring function

    - by volting
    I am trying to write a function to get a string from the uart1. Its for an embedded system so I don't want to use malloc. The pointer that is passed to the getstring function seems to point to garbage after the gets_e_uart1() is called. I don't use pointers too often so I'm sure it is something really stupid and trivial that Im doing wrong. Regards, V int main() { char *ptr = 0; while(1) { gets_e_uart1(ptr, 100); puts_uart1(ptr); } return 0; }*end main*/ //------------------------------------------------------------------------- //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char buffer_[SIZE_]; stringPtr_ = buffer_; int start_ = 0, end_ = SIZE_ - 1; char errorflag = 0; /*keep geting chars until newline char recieved*/ while((buffer_[start_++] = getchar_uart1())!= 0x0D) { putchar_uart1(buffer_[start_]);//echo it /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { start_ = 0; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { buffer_[0] = '\0'; errorflag = 1; } else { buffer_[start_++] = '\0'; } return errorflag; } Update: I decided to go with approach of passing a pointer an array to the function. This works nicely, thanks to everyone for the informative answers. Updated Code: //------------------------------------------------------------------------- //argument 1 should be a pointer to an array, //and the second argument should be the size of the array //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char *startPtr_ = stringPtr_; char *endPtr_ = startPtr_ + (SIZE_ - 1); char errorflag = 0; /*keep geting chars until newline char recieved*/ while((*stringPtr_ = getchar_uart1())!= 0x0D) { putchar_uart1(*stringPtr_);//echo it stringPtr_++; /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; *stringPtr_ = '\0'; errorflag = 1; } else { *stringPtr_ = '\0'; } return errorflag; }

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  • How to add a constructor to a subclassed numeric type?

    - by abbot
    I want to subclass a numeric type (say, int) in python and give it a shiny complex constructor. Something like this: class NamedInteger(int): def __init__(self, value): super(NamedInteger, self).__init__(value) self.name = 'pony' def __str__(self): return self.name x = NamedInteger(5) print x + 3 print str(x) This works fine under Python 2.4, but Python 2.6 gives a deprecation warning. What is the best way to subclass a numeric type and to redefine constructors for builtin types in newer Python versions?

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  • C: reading file and populating struct

    - by deostroll
    Hi, I have a structure with the following definition: typedef struct myStruct{ int a; char* c; int f; } OBJECT; I am able to populate this object and write it to a file. However I am not able to read the char* c value in it...while trying to read it, it gives me a segmentation fault error. Is there anything wrong with my code: //writensave.c #include "mystruct.h" #include <stdio.h> #include <string.h> #define p(x) printf(x) int main() { p("Creating file to write...\n"); FILE* file = fopen("struct.dat", "w"); if(file == NULL) { printf("Error opening file\n"); return -1; } p("creating structure\n"); OBJECT* myObj = (OBJECT*)malloc(sizeof(OBJECT)); myObj->a = 20; myObj->f = 45; myObj->c = (char*)calloc(30, sizeof(char)); strcpy(myObj->c, "This is a test"); p("Writing object to file...\n"); fwrite(myObj, sizeof(OBJECT), 1, file); p("Close file\n"); fclose(file); p("End of program\n"); return 0; } Here is how I am trying to read it: //readnprint.c #include "mystruct.h" #include <stdio.h> #define p(x) printf(x) int main() { FILE* file = fopen("struct.dat", "r"); char* buffer; buffer = (char*) malloc(sizeof(OBJECT)); if(file == NULL) { p("Error opening file"); return -1; } fread((void *)buffer, sizeof(OBJECT), 1, file); OBJECT* obj = (OBJECT*)buffer; printf("obj->a = %d\nobj->f = %d \nobj->c = %s", obj->a, obj->f, obj->c); fclose(file); return 0; }

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