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  • Java - What's the most efficient way of removing a set of elements from an Array[]

    - by fraido
    I've something like this Object[] myObjects = ...(initialized in some way)... int[] elemToRemove = new int[]{3,4,6,8,...} What's the most efficient way of removing the elements of index position 3,4,6,8... from myObjects ? I'd like to implement an efficient Utility method with a signature like public Object[] removeElements(Object[] object, int[] elementsToRemove) {...} The Object[] that is returned should be a new Object of size myObjects.length - elemToRemove.length

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  • Static member function pointer to hold non static member function

    - by user1425406
    This has defeated me. I want to have a static class variable which is a pointer to a (non-static) member function. I've tried all sorts of ways, but with no luck (including using typedefs, which just seemed to give me a different set of errors). In the code below I have the static class function pointer funcptr, and I can call it successfully from outside the class, but not from within the member function CallFuncptr - which is what I want to do. Any suggestions? #include <stdio.h> class A { public: static int (A::*funcptr)(); int Four() { return 4;}; int CallFuncptr() { return (this->*funcptr)(); } // doesn't link - undefined reference to `A::funcptr' }; int (A::*funcptr)() = &A::Four; int main() { A fred; printf("four? %d\n", (fred.*funcptr)()); // This works printf("four? %d\n", fred.CallFuncptr()); // But this is the way I want to call it }

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  • HashMap Memory Leak because of Dynamic Array

    - by Jake M
    I am attempting to create my own HashMap to understand how they work. I am using an array of Linked Lists to store the values(strings) in my hashmap. I am creating the array like this: Node** list; Instead of this: Node* list[nSize]; This is so the array can be any size at runtime. But I think I am getting a memory leak because of how I am doing this. I dont know where the error is but when I run the following simple code the .exe crashes. Why is my application crashing and how can I fix it? Note: I am aware that using a vector would be much better than an array but this is just for learning and I want to challenge myself to create the hashmap using a 'Dynamic' Array. PS: is that the correct term(Dynamic Array) for the kind of array I am using? struct Node { // to implement }; class HashMap { public: HashMap(int dynSize) { *list = new Node[dynSize]; size = dynSize; for (int i=0; i<size; i++) list[i] = NULL; cout << "END\n"; } ~HashMap() { for (int i=0; i<size; i++) delete list[i]; } private: Node** list; // I could use a vector here but I am experimenting with a pointer to an array(pointer), also its more elegant int size; }; int main() { // When I run this application it crashes. Where is my memory leak? HashMap h(5); system("PAUSE"); return 0; }

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  • Is it possible to run php exec through cygwin?

    - by Scarface
    Hey guys I have one command that works on my remote linux server but not my windows (WAMP package) local server. I really want to create an identical workstation so I can test locally and then update my remote server. If anyone has any suggestions or solutions other than converting to linux, I would really appreciate it. <?php $safe_path = escapeshellarg('fake-virus.txt'); $command = '/usr/bin/clamscan --stdout ' . $safe_path; $out = ''; $int = -1; exec($command, $out, $int); echo $int; if ($int == 0) { // all good; } else { echo 'o no';// VIRUS!; } ?>

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  • how to write binary copy of structure array to file

    - by cerr
    I would like to write a binary image of a structure array to a binary file. I have tried this so far: #include <stdio.h> #include <string.h> #define NUM 256 const char *fname="binary.bin"; typedef struct foo_s { int intA; int intB; char string[20]; }foo_t; void main (void) { foo_t bar[NUM]; bar[0].intA = 10; bar[0].intB = 999; strcpy(bar[0].string,"Hello World!"); Save(bar); printf("%s written succesfully!\n",fname); } int Save(foo_t* pData) { FILE *pFile; int ptr = 0; int itr = 0; pFile = fopen(fname, "w"); if (pFile == NULL) { printf("couldn't open %s\n", fname); return; } for (itr = 0; itr<NUM; itr++) { for (ptr=0; ptr<sizeof(foo_t); ptr++) { fputc((unsigned char)*((&pData[itr])+ptr), pFile); } fclose(pFile); } } but the compiler is saying aggregate value used where an integer was expected fputc((unsigned char)*((&pData[itr])+ptr), pFile); and I don't quite understand why, what am I doing wrong? Thanks!

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  • How to check if a position inside a std string exists ?? (c++)

    - by yox
    Hello, i have a long string variable and i want to search in it for specific words and limit text according to thoses words. Say i have the following text : "This amazing new wearable audio solution features a working speaker embedded into the front of the shirt and can play music or sound effects appropriate for any situation. It's just like starring in your own movie" and the words : "solution" , "movie". I want to substract from the big string (like google in results page): "...new wearable audio solution features a working speaker embedded..." and "...just like starring in your own movie" for that i'm using the code : for (std::vector<string>::iterator it = words.begin(); it != words.end(); ++it) { int loc1 = (int)desc.find( *it, 0 ); if( loc1 != string::npos ) { while(desc.at(loc1-i) && i<=80){ i++; from=loc1-i; if(i==80) fromdots=true; } i=0; while(desc.at(loc1+(int)(*it).size()+i) && i<=80){ i++; to=loc1+(int)(*it).size()+i; if(i==80) todots=true; } for(int i=from;i<=to;i++){ if(fromdots) mini+="..."; mini+=desc.at(i); if(todots) mini+="..."; } } but desc.at(loc1-i) causes OutOfRange exception... I don't know how to check if that position exists without causing an exception ! Help please!

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  • Using pow() for large number

    - by g4ur4v
    I am trying to solve a problem, a part of which requires me to calculate (2^n)%1000000007 , where n<=10^9. But my following code gives me output "0" even for input like n=99. Is there anyway other than having a loop which multilplies the output by 2 every time and finding the modulo every time (this is not I am looking for as this will be very slow for large numbers). #include<stdio.h> #include<math.h> #include<iostream> using namespace std; int main() { unsigned long long gaps,total; while(1) { cin>>gaps; total=(unsigned long long)powf(2,gaps)%1000000007; cout<<total<<endl; } }

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  • Bash PWD Shortening

    - by dlibby00
    I'm looking for a bash function that will shorten long path names to keep my PS1 variable from getting excessively long. Something along the lines of: /this/is/the/path/to/a/really/long/directory/i/would/like/shortened might end up as: /t../i../t../p../to/a/r../l../d../i/w../like/shortened something that the took the path and a maximum acceptable number of characters to shorten to would be perfect for my .bashrc file.

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  • Mysql query question

    - by brux
    I have 2 tables: Customer: customerid - int, pri-key,auto fname - varchar sname -varchar housenum - varchar street -varchar Items: itemid - int,pri-key,auto type - varchar collectiondate - date releasedate - date customerid - int I need a query which will get me all items that have a releasedate 3 days prior to (and including) the current date. i.e The query should return customerid,fname,sname,street,housenum,type,releasedate for all items which have releasedate within (and including)3 days prior today thanks in advance

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  • C++ Pointer Issue

    - by Winder
    _stuckVertices is an array of pointers and I would like to update one index of that array without using _stuckVertices[ (row * _cols) + column ] 3 times. The reason it is an array of pointers is because the vast majority of the time the pointer will be NULL. The following code works but I need to dereference a each time I use it: void Cloth::stickPoint(int column, int row) { Anchor **a = &_stuckVertices[ (row * _cols) + column ]; if (!*a) *a = new Anchor(this, column, row); (*a)->stick(); } I originally had it written like this, but the _stuckVertices pointer doesn't get updated: void Cloth::stickPoint(int column, int row) { Anchor *a = _stuckVertices[ (row * _cols) + column ]; if (!a) a = new Anchor(this, column, row); a->stick(); } Is there a way to write Anchor *a = _stuckVertices[ index ] so that a is like an alias into the array that I can update, or is something like the first piece of code how I should do this? Thanks

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  • Complex sorting on MySQL database

    - by ChrisR
    I'm facing the following situation. We've got an CMS with an entity with translations. These translations are stored in a different table with a one-to-many relationship. For example newsarticles and newsarticle_translations. The amount of available languages is dynamically determined by the same CMS. When entering a new newsarticle the editor is required to enter at least one translation, which one of the available languages he chooses is up to him. In the newsarticle overview in our CMS we would like to show a column with the (translated) article title, but since none of the languages are mandatory (one of them is mandatory but i don't know which one) i don't really know how to construct my mysql query to select a title for each newsarticle, regardless of the entered language. And to make it all a little harder, our manager asked for the possibilty to also be able to sort on title, so fetching the translations in a separate query is ruled out as far as i know. Anyone has an idea on how to solve this in the most efficient way? Here are my table schema's it it might help > desc news; +-----------------+----------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+----------------+------+-----+-------------------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | category_id | int(1) | YES | | NULL | | | created | timestamp | NO | | CURRENT_TIMESTAMP | | | user_id | int(10) | YES | | NULL | | +-----------------+----------------+------+-----+-------------------+----------------+ > desc news_translations; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | enabled | tinyint(1) | NO | | 0 | | | news_id | int(1) unsigned | NO | | NULL | | | title | varchar(255) | NO | | | | | summary | text | YES | | NULL | | | body | text | NO | | NULL | | | language | varchar(2) | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ PS: i've though about subqueries and coalesce() solutions but those seem rather dirty tricks, wondering if something better is know that i'm not thinking of?

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  • Cannot add or update a child row: a foreign key constraint fails

    - by Tom
    table 1 +----------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+-------------+------+-----+---------+----------------+ | UserID | int(11) | NO | PRI | NULL | auto_increment | | Password | varchar(20) | NO | | | | | Username | varchar(25) | NO | | | | | Email | varchar(60) | NO | | | | +----------+-------------+------+-----+---------+----------------+ table2 +------------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+--------------+------+-----+---------+----------------+ | UserID | int(11) | NO | MUL | | | | PostID | int(11) | NO | PRI | NULL | auto_increment | | Title | varchar(50) | NO | | | | | Summary | varchar(500) | NO | | | | +------------------+--------------+------+-----+---------+----------------+ com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (myapp/table2, CONSTRAINT table2_ibfk_1 FOREIGN KEY (UserID) REFERENCES table1 (UserID)) What have I done wrong? I read this: http://www.w3schools.com/Sql/sql_foreignkey.asp and i don't see whats wrong. :S

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  • Form graphics not set when form loads

    - by Jimmy
    My form has a group box which contains two overlapping rectangles. The form's other controls are two sets of four numeric up down controls to set the rectangles' colors. (nudF1,2,3 and 4 set the rectangle that's in front, and nudB1,2,3 and 4 set the rectangle that's behind.) Everything works fine, except that the rectangles do not display the colors set in the numeric up downs when the form first loads. The numeric up down controls' ChangeValue events all call the ShowColors() method. The form's Load event calls the csColorsForm_Load() method. Any suggestions? namespace csColors { public partial class csColorsForm : Form { public csColorsForm() { InitializeComponent(); } private void csColorsForm_Load(object sender, EventArgs e) { this.BackColor = System.Drawing.Color.DarkBlue; SetColors(sender, e); } private void SetColors(object sender, EventArgs e) { Control control = (Control)sender; String ctrlName = control.Name; Graphics objGraphics; Rectangle rect1, rect2; int colorBack, colorFore; objGraphics = this.grpColor.CreateGraphics(); // If calling control is not a forecolor control, paint backcolor rectangle if (ctrlName.Substring(0,4)!="nudF") { colorBack = int.Parse(SetColorsB("nudB"), NumberStyles.HexNumber); SolidBrush BrushB = new SolidBrush(Color.FromArgb(colorBack)); rect1 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushB, rect1); } // Always paint forecolor rectangle colorFore = int.Parse(SetColorsB("nudF"), NumberStyles.HexNumber); SolidBrush BrushF = new SolidBrush(Color.FromArgb(colorFore)); rect2 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushF, rect2); objGraphics.Dispose(); } private string SetColorsB(string nam) { string txt=""; for (int n = 1; n <= 4; ++n) { var ud = Controls[nam + n] as NumericUpDown; int hex = (int)ud.Value; txt += hex.ToString("X2"); } return txt; } private void btnClose_Click(object sender, EventArgs e) { this.Close(); } } }

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  • Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

    - by kpdvx
    An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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  • What's an elegant solution to get the property values from two classes (that have the same property

    - by SlipToFall
    Essentially I have to deal with a poorly implemented web service. They have two classes that don't derive from a parent class, but have the same properties (Ughh...). So it looks like this in my web service proxy class file: public partial class Product1 { public int Quantity; public int Price; } public partial class Product2 { public int Quantity; public int Price; } So what's the best way to grab the values from known properties without duplicating the code and casting to their respective classes? I know I probably could use reflection, but that can get ugly. If there is an easier less crazier way to do it (maybe in the new c# features?) please let me know.

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  • make a lazy var in scala

    - by ayvango
    Scala does not permit to create laze vars, only lazy vals. It make sense. But I've bumped on use case, where I'd like to have similar capability. I need a lazy variable holder. It may be assigned a value that should be calculated by time-consuming algorithm. But it may be later reassigned to another value and I'd like not to call first value calculation at all. Example assuming there is some magic var definition lazy var value : Int = _ val calc1 : () => Int = ... // some calculation val calc2 : () => Int = ... // other calculation value = calc1 value = calc2 val result : Int = value + 1 This piece of code should only call calc2(), not calc1 I have an idea how I can write this container with implicit conversions and and special container class. I'm curios if is there any embedded scala feature that doesn't require me write unnecessary code

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  • Assign the results of a stored procedure into a variable in another stored procedure

    - by RHPT
    The title of this question is a bit misleading, but I couldn't summarize this very well. I have two stored procedures. The first stored procedure (s_proc1) calls a second stored procedure (s_proc2). I want to assign the value returned from s_proc2 to a variable in s_proc1. Currently, I'm calling s_proc2 (inside s_proc1) in this manner: EXEC s_proc2 @SiteID, @count = @PagingCount OUTPUT s_proc2 contains a dynamic query statement (for reasons I will not outline here). CREATE dbo.s_proc2 ( @siteID int, @count int OUTPUT ) AS DECLARE @sSQL nvarchar(100) DECLARE @xCount int SELECT @sSQL = 'SELECT COUNT(ID) FROM Authors' EXEC sp_ExecuteSQL @sSQL, N'@xCount int output', @xCount output SET @count = @xCount RETURN @count Will this result in @PagingCount having the value of @count? I ask because the result I am getting from s_proc1 is wonky. In fact, what I do get is two results. The first being @count, then the result of s_proc1 (which is incorrect). So, it makes me wonder if @PagingCount isn't being set properly. Thank you.

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  • Why we can't we overload "=" using friend function?

    - by ashish-sangwan
    Why it is not allowed to overload "=" using friend function? I have written a small program but it is giving error. class comp { int real; int imaginary; public: comp(){real=0; imaginary=0;} void show(){cout << "Real="<<real<<" Imaginary="<<imaginary<<endl;} void set(int i,int j){real=i;imaginary=j;} friend comp operator=(comp &op1,const comp &op2); }; comp operator=(comp &op1,const comp &op2) { op1.imaginary=op2.imaginary; op1.real=op2.real; return op1; } int main() { comp a,b; a.set(10,20); b=a; b.show(); return 0; } The compilation gives the following error :- [root@dogmatix stackoverflow]# g++ prog4.cpp prog4.cpp:11: error: ‘comp operator=(comp&, const comp&)’ must be a nonstatic member function prog4.cpp:14: error: ‘comp operator=(comp&, const comp&)’ must be a nonstatic member function prog4.cpp: In function ‘int main()’: prog4.cpp:25: error: ambiguous overload for ‘operator=’ in ‘b = a’ prog4.cpp:4: note: candidates are: comp& comp::operator=(const comp&) prog4.cpp:14: note: comp operator=(comp&, const comp&)

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  • SQL swap field values

    - by Silence
    I have a SQL table (MYSQL 4.0 to be precise) composed of the following : int no (primary) int field1 int field2 I would like to swap the values of field1 with the values of field2 and vice-versa. Ex.: 1;2.5;3.76 becomes 1;3.76;2.5 I need a swapping temporary variable of some sort. But I don't think I can use something like Set @var1 = field1 inside my update statement. And I don't think altering the table to add a temporary column is my best best either.

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  • C++ pimpl idiom wastes an instruction vs. C style?

    - by Rob
    (Yes, I know that one machine instruction usually doesn't matter. I'm asking this question because I want to understand the pimpl idiom, and use it in the best possible way; and because sometimes I do care about one machine instruction.) In the sample code below, there are two classes, Thing and OtherThing. Users would include "thing.hh". Thing uses the pimpl idiom to hide it's implementation. OtherThing uses a C style – non-member functions that return and take pointers. This style produces slightly better machine code. I'm wondering: is there a way to use C++ style – ie, make the functions into member functions – and yet still save the machine instruction. I like this style because it doesn't pollute the namespace outside the class. Note: I'm only looking at calling member functions (in this case, calc). I'm not looking at object allocation. Below are the files, commands, and the machine code, on my Mac. thing.hh: class ThingImpl; class Thing { ThingImpl *impl; public: Thing(); int calc(); }; class OtherThing; OtherThing *make_other(); int calc(OtherThing *); thing.cc: #include "thing.hh" struct ThingImpl { int x; }; Thing::Thing() { impl = new ThingImpl; impl->x = 5; } int Thing::calc() { return impl->x + 1; } struct OtherThing { int x; }; OtherThing *make_other() { OtherThing *t = new OtherThing; t->x = 5; } int calc(OtherThing *t) { return t->x + 1; } main.cc (just to test the code actually works...) #include "thing.hh" #include <cstdio> int main() { Thing *t = new Thing; printf("calc: %d\n", t->calc()); OtherThing *t2 = make_other(); printf("calc: %d\n", calc(t2)); } Makefile: all: main thing.o : thing.cc thing.hh g++ -fomit-frame-pointer -O2 -c thing.cc main.o : main.cc thing.hh g++ -fomit-frame-pointer -O2 -c main.cc main: main.o thing.o g++ -O2 -o $@ $^ clean: rm *.o rm main Run make and then look at the machine code. On the mac I use otool -tv thing.o | c++filt. On linux I think it's objdump -d thing.o. Here is the relevant output: Thing::calc(): 0000000000000000 movq (%rdi),%rax 0000000000000003 movl (%rax),%eax 0000000000000005 incl %eax 0000000000000007 ret calc(OtherThing*): 0000000000000010 movl (%rdi),%eax 0000000000000012 incl %eax 0000000000000014 ret Notice the extra instruction because of the pointer indirection. The first function looks up two fields (impl, then x), while the second only needs to get x. What can be done?

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  • How to decrease size of c++ source code? [closed]

    - by free0u
    For example #include <iostream> using namespace std; int main() { freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); int n; cin >> n; for (int i = 0; i < n; i++) { cout << i; } return 0; } Decrease: #include <fstream> int main() { std::ifstream y("input.txt"); std::ofstream z("output.txt"); int n, i = 0; y >> n; while(i < n) z << i++; exit(0); } What's about "fstream"? std::fstream y("input.txt"), z("output.txt") It's amazing but output is not correct.) "output.txt" isn't remaking. Output is writing from begin of file. How to decrease code? Just for fun)

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  • Time complexity of a powerset generating function

    - by Lirik
    I'm trying to figure out the time complexity of a function that I wrote (it generates a power set for a given string): public static HashSet<string> GeneratePowerSet(string input) { HashSet<string> powerSet = new HashSet<string>(); if (string.IsNullOrEmpty(input)) return powerSet; int powSetSize = (int)Math.Pow(2.0, (double)input.Length); // Start at 1 to skip the empty string case for (int i = 1; i < powSetSize; i++) { string str = Convert.ToString(i, 2); string pset = str; for (int k = str.Length; k < input.Length; k++) { pset = "0" + pset; } string set = string.Empty; for (int j = 0; j < pset.Length; j++) { if (pset[j] == '1') { set = string.Concat(set, input[j].ToString()); } } powerSet.Add(set); } return powerSet; } So my attempt is this: let the size of the input string be n in the outer for loop, must iterate 2^n times (because the set size is 2^n). in the inner for loop, we must iterate 2*n times (at worst). 1. So Big-O would be O((2^n)*n) (since we drop the constant 2)... is that correct? And n*(2^n) is worse than n^2. if n = 4 then (4*(2^4)) = 64 (4^2) = 16 if n = 100 then (10*(2^10)) = 10240 (10^2) = 100 2. Is there a faster way to generate a power set, or is this about optimal?

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  • Please see following code and answer

    - by user323422
    template <class T> class _cExplicitInstation { public: void show1(T c) { double d =10.02 ; std::cout<<c; } void show2(T d) { std::cout<<d; } }; template _cExplicitInstation<char>; template void _cExplicitInstation<int>::show1(int c); int main() { _cExplicitInstation<char> abc; _cExplicitInstation<int>().show2(10);// it should show error as i have // explicitly declare for show1() function but its working // can u tell why? }

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  • How do you delete a pointer without deleting the data the pointer points to?

    - by Faken
    I have a pointer that points to an array and another pointer referencing the same array. How do i delete any one of those pointers without killing the array such that the second undeleted pointer still works? for example: int* pointer1 = new int [1000]; int* pointer2; pointer2 = pointer1; Now i want to get rid of pointer1, how would i do it such that i can continue to access the array normaly through pointer2?

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  • Query on the scope of local variables in C

    - by darkie15
    All, Consider the following code: void func(void) { int a; printf ("%d", a); } int main(int argc, char **argv) { int a = 3; func(); printf("%d", a); } According to my understanding, the output should be: <junk value><3> Can anyone please confirm my understanding? My basic query is, does the compiler refer to the outer scope for a variable that has been declared but not defined? Regards, darkie

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