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  • How do I use multiple where clauses in GHCi?

    - by T.R.
    I'm playing around with GHCi for the first time, and I'm having some trouble writing multi-line functions. My code is as follows: Prelude> :{ Prelude| let diffSquares lst = abs $ squareOfSums lst - sumOfSquares lst Prelude| where Prelude| squareOfSums lst = (fst (sumsAndSquares lst))^2 Prelude| sumOfSquares lst = snd (sumsAndSquares lst) Prelude| sumsAndSquares = foldl (\(sms,sqrs) x -> (sms+x,sqrs+x^2)) (0,0) Prelude| :} It gives the following error: <interactive>:1:142: parse error on input `=' Could someone kindly point me in the direction of what I'm missing?

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  • output with "Private`" Content in Mathematica Package

    - by madalina
    Hello everyone, I am trying to solve the following implementation problem in Mathematica 7.0 for some days now and I do not understand exactly what is happening so I hope someone can give me some hints. I have 3 functions that I implemented in Mathematica in a source file with extension *.nb. They are working okay to all the examples. Now I want to put these functions into 3 different packages. So I created three different packages with extension .*m in which I put all the desired Mathematica function. An example in the "stereographic.m" package which contain the code: BeginPackage["stereographic`"] stereographic::usage="The package stereographic...." formEqs::usage="The function formEqs[complexBivPolyEqn..." makePoly::usage="The function makePoly[algebraicEqn] ..." getFixPolys::usage="The function..." milnorFibration::usage="The function..." Begin["Private`"] Share[]; formEqs[complex_,{m_,n_}]:=Block[{complexnew,complexnew1, realeq, imageq, expreal, expimag, polyrealF, polyimagF,s,t,u,v,a,b,c,epsilon,x,y,z}, complexnew:=complex/.{m->s+I*t,n->u+I*v}; complexnew1:=complexnew/.{s->(2 a epsilon)/(1+a^2+b^2+c^2),t->(2 b epsilon)/(1+a^2+b^2+c^2),u->(2 c epsilon)/(1+a^2+b^2+c^2),v->(- epsilon+a^2 epsilon+b^2 epsilon+c^2 epsilon)/(1+a^2+b^2+c^2)}; realeq:=ComplexExpand[Re[complexnew1]]; imageq:=ComplexExpand[Im[complexnew1]]; expreal:=makePoly[realeq]; expimag:=makePoly[imageq]; polyrealF:=expreal/.{a->x,b->y,c->z}; polyimagF:=expimag/.{a->x,b->y,c->z}; {polyrealF,polyimagF} ] End[] EndPackage[] Now to test the function I load the package Needs["stereographic`"] everything is okay. But when I test the function for example with formEqs[x^2-y^2,{x,y}] I get the following ouput: {Private`epsilon^2 + 2 Private`x^2 Private`epsilon^2 + Private`x^4 Private`epsilon^2 - 6 Private`y^2 Private`epsilon^2 + 2 Private`x^2 Private`y^2 Private`epsilon^2 + Private`y^4 Private`epsilon^2 - 6 Private`z^2 Private`epsilon^2 + 2 Private`x^2 Private`z^2 Private`epsilon^2 + 2 Private`y^2 Private`z^2 Private`epsilon^2 + Private`z^4 Private`epsilon^2, 8 Private`x Private`y Private`epsilon^2 + 4 Private`z Private`epsilon^2 - 4 Private`x^2 Private`z Private`epsilon^2 - 4 Private`y^2 Private`z Private`epsilon^2 - 4 Private`z^3 Private`epsilon^2} Of course I do not understand why Private` appears in front of any local variable which I returned in the final result. I would want not to have this Private` in the computed output. Any idea or better explanations which could indicate me why this happens? Thank you very much for your help. Best wishes, madalina

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  • Dreamweaver javascript code hints

    - by xdevel2000
    I'd to use DW cs 4 but before to buy I want to test javascript code hints. However that feature doesn't work at all. I have an external .js library and then into an html file I load it but when I type functions or object by name nothing happen. Any idea?

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  • Multiple Projects, Common Module

    - by EShull
    I have a library of common functions that I use in several different projects, which works fine on my local machine where I can just add the path to the library, but now that I've put several of my projects on GoogleCode, I'm not sure how to deal with the external library. Do I put copies of it in each project and try to keep them all synchronized with each other, or is there a better way?

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  • asp.net c# ip address lost after postback?

    - by Mark
    Hi all, One of my functions in a class is called GetIpAddress() which returns the following string: System.Web.HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"] This all works well in regular page loads and gets my ip address, but when i for example let a user place a comment, then the ip address is lost after postback and i get an empty string returned. Am I missing something here maybe? Kind regards, Mark

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  • Where are the function literals in c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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  • C++ undefined reference

    - by klaus-johan
    Hi , My problem is the following : I have a class A that inherits from an abstract base class. I override all the virtual functions from the base class, and I have a constructor like this : A::A(B* b) { this->b=b; } In the constructor of class B , I have the following piece of code: A* a=new A(this) However this line of code gives the error : undefined reference to 'A::A(B*)' I have absolutly no idea why could this be happening , so any suggestion would be greatly appreciated !

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  • Find out why Xcode has decided to link to a particular library

    - by andygeers
    I'm using the Unity 3D engine to build an iPhone app, and when I go to generate my Xcode project for compilation, it includes a few fairly large libraries: Mono.Security.dll.s, System.dll.s, System.Core.dll.s, etc. I don't know if this question is really an Xcode question or a Unity question, but I'm trying to figure out why each of those libraries is being linked - which functions / classes are being referenced - ideally so that I can rewrite my code to remove as many of the dependencies as possible. Does anybody know a way to find this information out?

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  • How to handle duplicate values in d3.js

    - by Mario
    First I'm a d3.js noob :) How you can see from the title I've got a problem with duplicated data and aggregate the values is no option, because the name represent different bus stops. In this example maybe the stops are on the fron side and the back side of a building. And of course I like to show the names on the x-axis. If i created an example and the result is a bloody mess, see jsFiddel. x = index name = bus stop name n = value I've got a json e.g.: [{ "x": 0, "name": "Corniche St / Abu Dhabi Police GHQ", "n": 113 }, { "x": 1, "name": "Corniche St / Nation Towers", "n": 116 }, { "x": 2, "name": "Zayed 1st St / Al Khalidiya Public Garden", "n": 146 }, ... { "x": 49, "name": "Hamdan St / Tariq Bin Zeyad Mosque", "n": 55 }] The problem: It is possible that the name could appear more then once e.g. { "x": 1, "name": "Corniche St / Nation Towers", "n": 116 } and { "x": 4, "name": "Corniche St / Nation Towers", "n": 105 } I like to know is there a way to tell d3.js not to use distinct names and instead just show all names in sequence with their values. Any ideas or suggestions are very welcome :) If you need more information let me know. Thanks in advanced Mario

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  • PHP - ___ encoding to UTF-8 - is there an end-all solution?

    - by Kerry
    I've looked across the web, I've looked through SO, through PHP documentation and more. It seems like a ridiculous problem not to have a standard solution to. If you get an unknown character set, and it has strange characters (like english quotes), is there a standard way to convert them to UTF-8? I've seen many messy solutions using a plethora of functions and checking and none of them are definitely going to work. Has anyone come up with their own function or a solution that always works?

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  • Core Location and speed measurements

    - by Krumelur
    Does anyone know if Core Location in the iPhone OS uses anything but simple vector math to calculate speed? I've read that the GPS system can provide speed measurements that can be accurate when position is not (I believe using the Doppler shifts of the signals). I've tried and failed to see if the iPhone does this. The question is basically, does this data contain information or is it just convenience functions, using (filtered?) location data?

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  • Overloading new, delete in C++

    - by user265260
    i came across this line is stroustrup An operator function must either be a member or take at least one argument of a user-defined type (functions redefining the new and delete operators need not). Dont operator new and operator delete take an user defined type as one of their arguments? what does it mean, am i missing something here

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  • GL_MULTISAMPLING_ARB is not defined

    - by user146780
    I downloaded this: http://www.videotutorialsrock.com/opengl2.exe . I'm trying to follow a tutorial to setup multisampling but GL_MULTISAMPLING_ARB is not defined, and many necessary wgl functions do not seem to be defined. Wht's wrong exactly? Thanks

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  • color objects in C or C ++ [closed]

    - by jazz
    Possible Duplicate: Colors in C language i copied a game from a book which name is paratrooper i ask this question again i also provide the code of the objects which i create there i want to change the color of these objects but i didn't understand how to do that so can any one plz help me how to do that.Listen guys they are not the standard functions but i use the graphics library for these functions and i can't find the function in the library file of graphics. i hope u understand know.this code will not run properly so plz tell me something about the function which color it i can't put the image other wize i show u the image it will make alot easieer #include "graphics.h" #include "stdio.h" #include "conio.h" #include "process.h" #include "alloc.h" #include "stdlib.h" #include "math.h" #include "dos.h" main() { int gm=CGAHI, gd=CGA, key=0, area; initgraph(&gd, &gm, "C:\\tc\\bgi"); helidraw(246,50,-1); getch(); return 0; } helidraw ( int x, int y, int d ) { int direction, i, j ; if ( d ) direction = -1 ; else direction = 1 ; i = 3 ; j = 8 ; line ( x - j - 8, y - i - 2, x + j + 8, y - i - 2 ) ; line ( x - j + 5, y - i - 1, x + j - 5, y - i - 1 ) ; line ( x - j, y - i, x + j, y - i ) ; for ( ; i > 0 ; i--, j += 2 ) { putpixel ( x - ( direction * j ), y - i, 1 ) ; line ( x + ( direction * j ), y - i, x + ( direction * ( j - 8 ) ), y - i ) ; } i = 0 ; j -= 2 ; line ( x - ( direction * j ), y - i, x - ( direction * ( j + 17 ) ), y - i ) ; line ( x - ( direction * j ), y - i + 1, x - ( direction * ( j + 7 ) ), y - i + 1 ) ; putpixel ( x - ( direction * ( j + 19 ) ), y - i - 1, 1 ) ; for ( ; i < 3 ; i++, j -= 2 ) { putpixel ( x - j, y + i, 1 ) ; putpixel ( x + j, y + i, 1 ) ; } line ( x - j, y + i, x + j, y + i ) ; putpixel ( x - j + 3, y + i + 1, 1 ) ; putpixel ( x + j - 3, y + i + 1, 1 ) ; line ( x - j - 10, y + i + 2, x + j + 10, y + i + 2 ) ; putpixel ( x + ( direction * ( j + 12 ) ), y + i + 1, 1 ) ; }

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  • Why should GoTos be bad?

    - by lisn
    I'm using gotos and a lot of them. C++, PHP or COBOL - I use them on nearly all occasions where everybody else would use functions or even classes. Yet my code is Clear Maintainable Bug-free Fast So why does everybody I meet tell me about how bad gotos are? Are there any facts that show that they are "bad"?

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  • Does this incorporate JavaScript closures?

    - by alex
    In trying to learn JavaScript closures, I've confused myself a bit. From what I've gathered over the web, a closure is... Declaring a function within another function, and that inner function has access to its parent function's variables, even after that parent function has returned. Here is a small sample of script from a recent project. It allows text in a div to be scrolled up and down by buttons. var pageScroll = (function() { var $page, $next, $prev, canScroll = true, textHeight, scrollHeight; var init = function() { $page = $('#secondary-page'); // reset text $page.scrollTop(0); textHeight = $page.outerHeight(); scrollHeight = $page.attr('scrollHeight'); if (textHeight === scrollHeight) { // not enough text to scroll return false; }; $page.after('<div id="page-controls"><button id="page-prev">prev</button><button id="page-next">next</button></div>'); $next = $('#page-next'); $prev = $('#page-prev'); $prev.hide(); $next.click(scrollDown); $prev.click(scrollUp); }; var scrollDown = function() { if ( ! canScroll) return; canScroll = false; var scrollTop = $page.scrollTop(); $prev.fadeIn(500); if (scrollTop == textHeight) { // can we scroll any lower? $next.fadeOut(500); } $page.animate({ scrollTop: '+=' + textHeight + 'px'}, 500, function() { canScroll = true; }); }; var scrollUp = function() { $next.fadeIn(500); $prev.fadeOut(500); $page.animate({ scrollTop: 0}, 500); }; $(document).ready(init); }()); Does this example use closures? I know it has functions within functions, but is there a case where the outer variables being preserved is being used? Am I using them without knowing it? Thanks Update Would this make a closure if I placed this beneath the $(document).ready(init); statement? return { scrollDown: scrollDown }; Could it then be, if I wanted to make the text scroll down from anywhere else in JavaScript, I could do pageScroll.scrollDown(); I'm going to have a play around on http://www.jsbin.com and report back

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  • How to combine query strings in PHP

    - by incrediman
    Given a url, and a query string, how can I get the url resulting from the combination of the query string with the url? I'm looking for functionality similar to .htaccess's qsa. I realize this would be fairly trivial to implement completely by hand, however are there built-in functions that deal with query strings which could either simplify or completely solve this? Example input/result sets: Url="http://www.example.com/index.php/page?a=1" QS ="?b=2" Result="http://www.example.com/index.php/page?a=1&b=2" - Url="page.php" QS ="?b=2" Result="page.php?b=2"

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  • How do you return a pointer to a base class with a virtual function?

    - by Nick Sweet
    I have a base class called Element, a derived class called Vector, and I'm trying to redefine two virtual functions from Element in Vector. //element.h template <class T> class Element { public: Element(); virtual Element& plus(const Element&); virtual Element& minus(const Element&); }; and in another file //Vector.h #include "Element.h" template <class T> class Vector: public Element<T> { T x, y, z; public: //constructors Vector(); Vector(const T& x, const T& y = 0, const T& z =0); Vector(const Vector& u); ... //operations Element<T>& plus(const Element<T>& v) const; Element<T>& minus(const Element<T>& v) const; ... }; //sum template <class T> Element<T>& Vector<T>::plus(const Element<T>& v) const { Element<T>* ret = new Vector((x + v.x), (y + v.y), (z + v.z)); return *ret; } //difference template <class T> Element<T>& Vector<T>::minus(const Element<T>& v) const { Vector<T>* ret = new Vector((x - v.x), (y - v.y), (z - v.z)); return *ret; } but I always get error: 'const class Element' has no member named 'getx' So, can I define my virtual functions to take Vector& as an argument instead, or is there a way for me to access the data members of Vector through a pointer to Element? I'm still fairly new to inheritance polymorphism, fyi.

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  • What is the corrrect way to increment a field making up part of a composit key

    - by Tr1stan
    I have a bunch of tables whose primary key is made up of the foreign keys of other tables (Composite key). Therefore for example the attributes (as a very cut down version) might look like this: A[aPK, SomeFields] 1:M B[bPK, aFK, SomeFields] 1:M C[cPK, bFK, aFK, SomeFields] as data this could look like: A[aPK, SomeFields]: 1, Foo 2, Bar B[bPK, aFK, SomeFields]: 1, 1, FooData1 2, 1, FooData2 1, 2, BarData1 2, 2, BarData2 C[cPK, bFK, aFK, SomeFields]: 1, 1, 1, FooData1More 2, 1, 1, FooData1More 1, 2, 1, FooData2More 2, 2, 1, FooData2More 1, 1, 2, BarData1More 2, 1, 2, BarData1More 1, 2, 2, BarData2More 2, 2, 2, BarData2More I've got this running in a MSSQL DBMS and I'm looking for the best way to increment the left most column, in each table when a new tuple is added to it. I can't use the Auto Increment Identity Specification option as that has no idea that it is part of a composite key. I also don't want to use any aggregate function such as: MAX(field)+1 as this will have adverse affects with multiple users inputting data, rolling back etc. There might however be a nice trigger based option here, but I'm not sure. This must be a common issue so I'm hoping that someone has a lovely solution. As a side which may or may not affect the answer, I'm using Entity Framework 1.0 as my ORM, within a c# MVC application.

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  • Numpy: Creating a complex array from 2 real ones?

    - by Duncan Tait
    I swear this should be so easy... Why is it not? :( In fact, I want to combine 2 parts of the same array to make a complex array: Data[:,:,:,0] , Data[:,:,:,1] These don't work: x = np.complex(Data[:,:,:,0], Data[:,:,:,1]) x = complex(Data[:,:,:,0], Data[:,:,:,1]) Am I missing something? Does numpy not like performing array functions on complex numbers? Here's the error: TypeError: only length-1 arrays can be converted to Python scalars Cheers

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