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• Invalid conversion from int to int** C++

  - by user69514

  Not sure why I'm getting this error. I have the following: int* arr = new int[25]; int* foo(){ int* i; cout << "Enter an integer:"; cin >> *i; return i; } void test(int** myInt){ *myInt = foo(); } This call here is where I get the error: test(arr[0]); //here i get invalid conversion from int to int**

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• Using php's magic function inside another function does not work

  - by Sirber

  I want to use magic function __set() and __get() for storing SQL data inside a php5 class and I get some strange issue using them inside a function: Works: if (!isset($this->sPrimaryKey) || !isset($this->sTable)) return false; $id = $this->{$this->sPrimaryKey}; if (empty($id)) return false; echo 'yaay!'; Does not work: if (!isset($this->sPrimaryKey) || !isset($this->sTable)) return false; if (empty($this->{$this->sPrimaryKey})) return false; echo 'yaay!'; would this be a php bug?

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• Haskell IO Passes to Another Function

  - by peterwkc

  This question here is related to http://stackoverflow.com/questions/3066956/haskell-input-return-tuple I wonder how we can passes the input from monad IO to another function in order to do some computation. Actually what i want is something like -- First Example test = savefile investinput -- Second Example maxinvest :: a maxinvest = liftM maximuminvest maxinvestinput maxinvestinput :: IO() maxinvestinput = do str <- readFile "C:\\Invest.txt" let cont = words str let mytuple = converttuple cont let myint = getint mytuple putStrLn "" -- Convert to Tuple converttuple :: [String] -> [(String, Integer)] converttuple [] = [] converttuple (x:y:z) = (x, read y):converttuple z -- Get Integer getint :: [(String, Integer)] -> [Integer] getint [] = [] getint (x:xs) = snd (x) : getint xs -- Search Maximum Invest maximuminvest :: (Ord a) => [a] -> a maximuminvest [] = error "Empty Invest Amount List" maximuminvest [x] = x maximuminvest (x:xs) | x > maxTail = x | otherwise = maxTail where maxTail = maximuminvest xs In the second example, the maxinvestinput is read from file and convert the data to the type maximuminvest expected. Please help. Thanks.

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• Passing a 2D array to a function in C

  - by Tyler Treat

  I have, essentially, a matrix of data (lets say ints) that I would like to store in a 2D array in which the dimensions are not known until runtime (say x columns and y rows). I want to populate the array in a function, so I assume I need to do something like this: int main(int argc, char **argv) { int y = atoi(argv[1]); int x = atoi(argv[2]); int **matrix = malloc(x * sizeof(int*)); populateMatrix(matrix, y, x); return 0; } void populateMatrix(**matrix, int y, int x) { int i, j; for (i = 0; i < y; i++) { for (j = 0; j < x; j++) { matrix[i][j] = i * j; // populated with trivial data to keep it simple } } } Obviously this doesn't work, but I'm not sure how to do what I'm describing exactly.

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• Javascript function as a parameter to another function?

  - by Alex

  Hello there, I'm learning lots of javascript these days, and one of the things I'm not quite understanding is passing functions as parameters to other functions. I get the concept of doing such things, but I myself can't come up with any situations where this would be ideal? My question is: When do you want to have your javascript functions take another function as a parameter? Why not just assign a variable to that functions return value and pass that variable to the function like so: // Why not do this var foo = doStuff(params); callerFunction(foo); //instead of this callerFunction(doStuff); I'm confused as to why I would ever choose to do things as in my second example. Why would you do this? What are the use cases? Thanks!!

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• Returning a local object from a function

  - by pocoa

  Is this the right way to return an object from a function? Car getCar(string model, int year) { Car c(model, year); return c; } void displayCar(Car &car) { cout << car.getModel() << ", " << car.getYear() << endl; } displayCar(getCar("Honda", 1999)); I'm getting an error, "taking address of temporary". Should I use this way: Car &getCar(string model, int year) { Car c(model, year); return c; }

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• template class: ctor against function -> new C++ standard

  - by Oops

  Hi in this question: http://stackoverflow.com/questions/2779155/template-point2-double-point3-double Dennis and Michael noticed the unreasonable foolishly implemented constructor. They were right, I didn't consider this at that moment. But I found out that a constructor does not help very much for a template class like this one, instead a function is here much more convenient and safe namespace point { template < unsigned int dims, typename T > struct Point { T X[ dims ]; std::string str() { std::stringstream s; s << "{"; for ( int i = 0; i < dims; ++i ) { s << " X" << i << ": " << X[ i ] << (( i < dims -1 )? " |": " "); } s << "}"; return s.str(); } Point<dims, int> toint() { Point<dims, int> ret; std::copy( X, X+dims, ret.X ); return ret; } }; template < typename T > Point< 2, T > Create( T X0, T X1 ) { Point< 2, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; return ret; } template < typename T > Point< 3, T > Create( T X0, T X1, T X2 ) { Point< 3, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; ret.X[ 2 ] = X2; return ret; } template < typename T > Point< 4, T > Create( T X0, T X1, T X2, T X3 ) { Point< 4, T > ret; ret.X[ 0 ] = X0; ret.X[ 1 ] = X1; ret.X[ 2 ] = X2; ret.X[ 3 ] = X3; return ret; } }; int main( void ) { using namespace point; Point< 2, double > p2d = point::Create( 12.3, 34.5 ); Point< 3, double > p3d = point::Create( 12.3, 34.5, 56.7 ); Point< 4, double > p4d = point::Create( 12.3, 34.5, 56.7, 78.9 ); //Point< 3, double > p1d = point::Create( 12.3, 34.5 ); //no suitable user defined conversion exists //Point< 3, int > p1i = p4d.toint(); //no suitable user defined conversion exists Point< 2, int > p2i = p2d.toint(); Point< 3, int > p3i = p3d.toint(); Point< 4, int > p4i = p4d.toint(); std::cout << p2d.str() << std::endl; std::cout << p3d.str() << std::endl; std::cout << p4d.str() << std::endl; std::cout << p2i.str() << std::endl; std::cout << p3i.str() << std::endl; std::cout << p4i.str() << std::endl; char c; std::cin >> c; } has the new C++ standard any new improvements, language features or simplifications regarding this aspect of ctor of a template class? what do you think about the implementation of the combination of namespace, stuct and Create function? many thanks in advance Oops

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• How to do an if statement on a function in PHP?

  - by Bruce

  I just realized that you can't just use an if statement on a function, for example this doesn't work: function sayHello() { echo "Hello World"; } if(sayHello()) echo "Function Worked"; else echo "Function Failed"; I also saw that a function can't be put as the value of a variable. So how can I do an if statement to check if a function has executed properly and display it to the browser?

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• Template meta-programming with member function pointers?

  - by wheaties

  Is it possible to use member function pointers with template meta-programming? Such as: class Connection{ public: string getName() const; string getAlias() const; //more stuff }; typedef string (Connection::*Con_Func)() const; template<Con_Func _Name> class Foo{ Connection m_Connect; public: void Foo(){ cout << m_Connect.(*_Name); } }; typedef Foo<&Connection::getName> NamedFoo; typedef Foo<&Connection::getAlias> AliasFoo; Granted, this is rather contrived but is it possible? (yes, there are probably much better ways but humor me.)

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• Const Member function Vs Const Friend Function

  - by strut

  How this code modifies a value in a const function: http://www.ideone.com/vjVsf And this code gives an error: http://www.ideone.com/346Xg

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• Creating a function that will handle objects with common properties

  - by geocine

  Take this as an example I have trimmed this example for readability and you may not find the use of this concept here. class Teacher() { public Name {get; set;} public Salt {get; set;} public Department{get; set;} } class Student() { public Name {get; set;} public Salt {get; set;} public Section{get; set;} } public string GetEncryptedName(object Person) { //return encrypted name based on Name and Salt property return encrypt(object.Salt,object.Name) } callig the function GetEncryptedName(Teacher) GetEncryptedName(Student) How do you implement this kind of stuff?

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• "Inline" function call: function is never hit

  - by Shimrod

  Hi everybody. I'm trying to make a tabbed menu for the asp.net website I'm working on. One of the pre-requisite is obviously to color the current tab differently, so the user can know on which tab is currently is. To do this, I made this method in my code-behind: Protected Function GetCssClass(ByVal ctrl As LinkButton) As String If ctrl.ID = currentLink Then Return "current" Else Return String.Empty End If End Function and I call the method like this in my aspx page: <asp:LinkButton ID="LinkButton1" runat="server" PostBackUrl="/Default.aspx" CssClass="<%#GetCssClass(LinkButton1) %>" >Home</asp:LinkButton> <asp:LinkButton ID="LinkButton2" runat="server" PostBackUrl="/Directory/page1.aspx" CssClass="<%#GetCssClass(LinkButton2) %>" >Page1</asp:LinkButton> But the method is never hit... As I understand, the method should be called each time the LinkButton is drawn... Does someone have an idea why? Thanks in advance !

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• Possible to change function name in definition?

  - by Bird Jaguar IV

  I tried several ways to change the function name in the definition, but they failed. >>> def f(): pass >>> f.__name__ 'f' >>> def f(): f.__name__ = 'new name' >>> f.__name__ 'f' >>> def f(): self.__name__ = 'new name' >>> f.__name__ 'f' But I can change the name attribute after defining it. >>> def f(): pass >>> f.__name__ = 'new name' >>> f.__name__ 'new name' Any way to change/set it in the definition (other than using a decorator)?

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• Function declaration in C and C++

  - by Happy Mittal

  I have two C++ files, say file1.cpp and file2.cpp as //file1.cpp #include<cstdio> void fun(int i) { printf("%d\n",i); } //file2.cpp void fun(double); int main() { fun(5); } When I compile them and link them as c++ files, I get an error "undefined reference to fun(double)". But when I do this as C files, I don't get error and 0 is printed instead of 5. Please explain the reason. Moreover I want to ask whether we need to declare a function before defining it because I haven't declared it in file1.cpp but no error comes in compilation.

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• Android Camera takePicture function does not call Callback function

  - by Tomáš 'Guns Blazing' Frcek

  I am working on a custom Camera activity for my application. I was following the instruction from the Android Developers site here: http://developer.android.com/guide/topics/media/camera.html Everything seems to works fine, except the Callback function is not called and the picture is not saved. Here is my code: public class CameraActivity extends Activity { private Camera mCamera; private CameraPreview mPreview; private static final String TAG = "CameraActivity"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.camera); // Create an instance of Camera mCamera = getCameraInstance(); // Create our Preview view and set it as the content of our activity. mPreview = new CameraPreview(this, mCamera); FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview); preview.addView(mPreview); Button captureButton = (Button) findViewById(R.id.button_capture); captureButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Log.v(TAG, "will now take picture"); mCamera.takePicture(null, null, mPicture); Log.v(TAG, "will now release camera"); mCamera.release(); Log.v(TAG, "will now call finish()"); finish(); } }); } private PictureCallback mPicture = new PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { Log.v(TAG, "Getting output media file"); File pictureFile = getOutputMediaFile(); if (pictureFile == null) { Log.v(TAG, "Error creating output file"); return; } try { FileOutputStream fos = new FileOutputStream(pictureFile); fos.write(data); fos.close(); } catch (FileNotFoundException e) { Log.v(TAG, e.getMessage()); } catch (IOException e) { Log.v(TAG, e.getMessage()); } } }; private static File getOutputMediaFile() { String state = Environment.getExternalStorageState(); if (!state.equals(Environment.MEDIA_MOUNTED)) { return null; } else { File folder_gui = new File(Environment.getExternalStorageDirectory() + File.separator + "GUI"); if (!folder_gui.exists()) { Log.v(TAG, "Creating folder: " + folder_gui.getAbsolutePath()); folder_gui.mkdirs(); } File outFile = new File(folder_gui, "temp.jpg"); Log.v(TAG, "Returnng file: " + outFile.getAbsolutePath()); return outFile; } } After clicking the Button, I get logs: "will now take picture", "will now release camera" and "will now call finish". The activity finishes succesfully, but the Callback function was not called during the mCamera.takePicture(null, null, mPicture); function (There were no logs from the mPicture callback or getMediaOutputFile functions) and there is no file in the location that was specified. Any ideas? :) Much thanks!

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• Member Function Pointer not quite right

  - by BlackDuck

  I have a SpecialisedRedBlackTree class that is templated. My Month class is not. In my Month class I have a private member which is an instance of SpecialisedRedBlackTree: SpecialisedRedBlackTree<Day> m_windSpeedTree; As you can see it will take the Day class/object (please correct me on any terms I get wrong). In my Month class, I have a method passing a method function pointer to this method: bool Month::CompareWindSpeed(Day a, Day b) { return ( a.GetData(WIND_SPEED_CODE) < b.GetData(WIND_SPEED_CODE)? true : false); } bool (Month::*myFuncPtr)(Day, Day); myFuncPtr = &Month::CompareWindSpeed; m_windSpeedTree.Insert(dayReading, myFuncPtr); But because I am passing a bool (Day, Day) pointer to a templated class expecting bool (T, T) T being part of this .... template Error 1 error C2664: 'SpecialisedRedBlackTree<T>::Insert' : cannot convert parameter 2 from 'bool (__thiscall Month::* )(Day,Day)' to 'bool (__cdecl *)(T,T)' Any advice?

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• NSPredicate aggregate function [SIZE] gives 'unsupported function expression' error

  - by jinglesthula

  iOS 4: I have entities in Core Data (using SQLite, which is a requirement) of: Request Response (which has a property personId) Revision Relationships are: Request <-- Revision Request <-- Response Revision <-- Response (e.g. each request may have many responses; each request/response pair may have many revisions) I'm trying to do a predicate to get all Responses with a given personId that have zero Revisions. Using: (personId == %d) && (Request.Revision[SIZE] == 0) in my predicate string gives me a runtime exception "Unsupported function expression Request.Revision[SIZE]" The documentation seems pretty sparse on aggregate functions, only noting that they exist, but with no syntax or examples. Not sure if it's my syntax or if the SIZE function really isn't supported in iOS.

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• Pass the current state of a function into another function in C/C++

  - by sand

  Is there a way to pass the current state of a function into another function in C/C++? I mean all the parameters and local variables by current state. For example: void funcA (int a, int b) { char c; int d, e; // Do something with the variables. // ... funcB(); // Do something more. } void funcB() { // funcB() should be able to access variables a,b,c,d & e // and any change in these variables reflect into funcA(). } The code is in bad shape if there is a need for funcB() kind of functions. But can it be achieved? This can help if someone is starting to re-factor a long method with multiple parameters.

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• C++ Function Calling Itself

  - by Ben

  Suppose I wish to have a function that fills an array either in pattern x,y,x,y,x,ywhere x and y are variables defined by some algorithm and x,y,z,x,y,z where x, y and z are variables defined by the same algorithm. This should continue for all number of variables. Is this a viable way to implement it. int recurse_n(int n) { while(n > 0) { --n; recurse_n(n); n = 0; // Use algorithm here } }

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• convert function from Access SQL to T-SQL 2005

  - by Pace

  Can someone please convert this access sql function for me to work in t-sql 2005. I am tring to take the selling price minus the cost as one number. And divide that by the original selling price to produce a second number Thanks :) =IIf([Selling Price]=0,0,([Selling Price]-Nz([Cost]))/[Selling Price]) IIRC it should be something along the lines of; ISNULL((ISNULL([Selling Price],0) - ISNULL(Cost,0)),0) / ISNULL([Selling Price],0) AS Margin But here I am getting a divide by Zero error. any suggestions?

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• fancybox - passing 'this' to onClosed function

  - by Phil Jackson

  Hi this is probly really simple but I juast cant seem to figure it out! if( is_logged_out( html ) ) { var throughClick = $(this); $.fancybox( html, { 'autoDimensions' : false, 'width' : 'auto', 'height' : 'auto', 'transitionIn' : 'none', 'transitionOut' : 'none', 'hideOnOverlayClick' : false, 'showCloseButton' : false, 'onClosed' : function( throughClick ) { alert(throughClick.attr('name')); throughClick.trigger('click'); } }); }else{ All i want to do is pass the object of whichever button or link that was clicked, so once the user has logged back in it will process again. Any help is much appreciated.

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• passing different structs to a function in c

  - by clear2k

  I have different structures that need to be filled out the same way. The only difference is that they are filled based on different data. I was wondering if it's possible to pass different structures to a certain function. What I have in mind is something like: struct stu1 { char *a; int b; }; struct stu2 { char *a; int b; }; static struct not_sure **some_func(struct not_sure *not_sure_here, original_content_list) { // do something and return passed struct for(i=0; i<size_of_original_content_list; i++){ //fill out passed structure } return the_struct; } int main(int argc, char *argv[]) { return_struct1 = some_func(stu1); return_struct2 = some_func(stu2); // do something separate with each return struct... } Any comments will be appreciate it.

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• sql charateristic function for avg dates

  - by holden

  I have a query which I use to grab specific dates and a price for the date, but now I'd like to use something similar to grab the avg prices for particular days of the week. Here's my current query which works for specific dates to pull from a table called availables: SELECT rooms.name, rooms.roomtype, rooms.id, max(availables.updated_at), MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 0, (availables.price*0.66795805223432), '')) AS day1, MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 1, (availables.price*0.66795805223432), '')) AS day2, MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 2, (availables.price*0.66795805223432), '')) AS day3, MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 3, (availables.price*0.66795805223432), '')) AS day4, MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 4, (availables.price*0.66795805223432), '')) AS day5, MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 5, (availables.price*0.66795805223432), '')) AS day6, MAX(IF(to_days(availables.bookdate) - to_days('2009-12-10') = 6, (availables.price*0.66795805223432), '')) AS day7, MIN(spots) as spots FROM `availables` INNER JOIN rooms ON availables.room_id=rooms.id WHERE rooms.hotel_id = '5064' AND bookdate BETWEEN '2009-12-10' AND DATE_ADD('2009-12-10', INTERVAL 6 DAY) GROUP BY rooms.name ORDER BY rooms.ppl My first stab which doesn't work, probably because the DAYSOFWEEK function is much different from the to_days... SELECT rooms.id, rooms.name, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 0, (availables.price*0.66795805223432), '')) AS day1, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 1, (availables.price*0.66795805223432), '')) AS day2, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 2, (availables.price*0.66795805223432), '')) AS day3, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 3, (availables.price*0.66795805223432), '')) AS day4, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 4, (availables.price*0.66795805223432), '')) AS day5, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 5, (availables.price*0.66795805223432), '')) AS day6, MAX(IF(DAYOFWEEK(availables.bookdate) - DAYOFWEEK('2009-12-10') = 6, (availables.price*0.66795805223432), '')) AS day7,rooms.ppl AS spots FROM `availables` INNER JOIN `rooms` ON `rooms`.id = `availables`.room_id WHERE (rooms.hotel_id = 5064 AND rooms.ppl > 3 AND availables.price > 0 AND availables.spots > 1) GROUP BY rooms.name ORDER BY rooms.ppl Maybe i'm making this crazy hard and someone knows a much simpler way. It takes data that looks like this #Availables id room_id price spots bookdate 1 26 $5 5 2009-10-20 2 26 $6 5 2009-10-21 to: +----+-------+--------------------+---------------------+---------------------+---------------------+------+------+------+------+ | id | spots | name | day1 | day2 | day3 | day4 | day5 | day6 | day7 | +----+-------+--------------------+---------------------+---------------------+---------------------+------+------+------+------+ | 25 | 4 | Blue Room | 14.9889786921381408 | 14.9889786921381408 | 14.9889786921381408 | | | | | | 26 | 6 | Whatever | 13.7398971344599624 | 13.7398971344599624 | 13.7398971344599624 | | | | | | 27 | 8 | Some name | 11.2417340191036056 | 11.2417340191036056 | 11.2417340191036056 | | | | | | 28 | 8 | Another | 9.9926524614254272 | 9.9926524614254272 | 9.9926524614254272 | | | | | | 29 | 10 | Stuff | 7.4944893460690704 | 7.4944893460690704 | 7.4944893460690704 | | | | | +----+-------+--------------------+---------------------+---------------------+---------------------+------+------+------+---

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• C++ Newbie: Passing an fstream to a function to read data

  - by vgm64

  I have a text file named num.txt who's only contents is the line 123. Then I have the following: void alt_reader(ifstream &file, char* line){ file.read(line, 3); cout << "First Time: " << line << endl; } int main() { ifstream inFile; int num; inFile.open("num.txt"); alt_reader(inFile, (char*)&num); cout << "Second Time: " << num << endl; } The output is: First Time: 123 Second Time: 3355185 Can you help me figure out how to get an fstream that is read in a function still assign the variable in main? I'm doing this because alt_reader really has a lot more to it, but this is the part I'm stuck on. Thanks a lot for the help.

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• A function where small changes in input always result in large changes in output

  - by snowlord

  I would like an algorithm for a function that takes n integers and returns one integer. For small changes in the input, the resulting integer should vary greatly. Even though I've taken a number of courses in math, I have not used that knowledge very much and now I need some help... An important property of this function should be that if it is used with coordinate pairs as input and the result is plotted (as a grayscale value for example) on an image, any repeating patterns should only be visible if the image is very big. I have experimented with various algorithms for pseudo-random numbers with little success and finally it struck me that md5 almost meets my criteria, except that it is not for numbers (at least not from what I know). That resulted in something like this Python prototype (for n = 2, it could easily be changed to take a list of integers of course): import hashlib def uniqnum(x, y): return int(hashlib.md5(str(x) + ',' + str(y)).hexdigest()[-6:], 16) But obviously it feels wrong to go over strings when both input and output are integers. What would be a good replacement for this implementation (in pseudo-code, python, or whatever language)?

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