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  • Pointer to a C++ class member function as a global function's parameter?

    - by marcin1400
    I have got a problem with calling a global function, which takes a pointer to a function as a parameter. Here is the declaration of the global function: int lmdif ( minpack_func_mn fcn, void *p, int m, int n, double *x, double *fvec, double ftol) The "minpack_func_mn" symbol is a typedef for a pointer to a function, defined as: typedef int (*minpack_func_mn)(void *p, int m, int n, const double *x, double *fvec, int iflag ); I want to call the "lmdif" function with a pointer to a function which is a member of a class I created, and here is the declaration of this class function: int LT_Calibrator::fcn(void *p, int m, int n, const double *x, double *fvec,int iflag) I am calling a global function like this: info=lmdif(&LT_Calibrator::fcn, 0, m, n, x, fvec, ftol) Unfortunately, I get a compiler error, which says: "error C2664: 'lmdif' : cannot convert parameter 1 from 'int (__thiscall LT_Calibrator::* )(void *,int,int,const double *,double *,int)' to 'minpack_func_mn' 1 There is no context in which this conversion is possible" Is there any way to solve that problem?

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  • Haskell function composition (.) and function application ($) idioms: correct use.

    - by Robert Massaioli
    I have been reading Real World Haskell and I am nearing the end but a matter of style has been niggling at me to do with the (.) and ($) operators. When you write a function that is a composition of other functions you write it like: f = g . h But when you apply something to the end of those functions I write it like this: k = a $ b $ c $ value But the book would write it like this: k = a . b . c $ value Now to me they look functionally equivalent, they do the exact same thing in my eyes. However, the more I look, the more I see people writing their functions in the manner that the book does: compose with (.) first and then only at the end use ($) to append a value to evaluate the lot (nobody does it with many dollar compositions). Is there a reason for using the books way that is much better than using all ($) symbols? Or is there some best practice here that I am not getting? Or is it superfluous and I shouldn't be worrying about it at all? Thanks.

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  • How cast in c#/.net 3.5 works? for types with '?'

    - by Inez
    This is my code which works public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : (decimal?) null; } and this one doesn't work public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : null; } giving the compilator error: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'decimal' and '' I wonder why? any ideas?

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  • How does cast in C#/.NET 3.5 work for types with '?'

    - by Inez
    This is my code which works public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : (decimal?) null; } and this one doesn't work public decimal? Get() { var res = ... return res.Count() > 0 ? res.First() : null; } giving the compiler error: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'decimal' and '<null>' I wonder why? any ideas?

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  • C++ UTF-8 output with ICU

    - by Isaac
    I'm struggling to get started with the C++ ICU library. I have tried to get the simplest example to work, but even that has failed. I would just like to output a UTF-8 string and then go from there. Here is what I have: #include <unicode/unistr.h> #include <unicode/ustream.h> #include <iostream> int main() { UnicodeString s = UNICODE_STRING_SIMPLE("??????"); std::cout << s << std::endl; return 0; } Here is the output: $ g++ -I/sw/include -licucore -Wall -Werror -o icu_test main.cpp $ ./icu_test пÑÐ¸Ð²ÐµÑ My terminal and font support UTF-8 and I regularly use the terminal with UTF-8. My source code is in UTF-8. I think that perhaps I somehow need to set the output stream to UTF-8 because ICU stores strings as UTF-16, but I'm really not sure and I would have thought that the operators provided by ustream.h would do that anyway. Any help would be appreciated, thank you.

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  • How do I Convert ARGB value from string to colour?

    - by James
    I am trying to use the MakeColor method in the GDIPAPI unit but the conversion from int to byte is not returning me the correct value. Example var argbStr: string; A, R, G, B: Byte; begin argbStr := 'ffffcc88'; A := StrToInt('$' + Copy(AValue, 1, 2)); R := StrToInt('$' + Copy(AValue, 3, 2)); G := StrToInt('$' + Copy(AValue, 5, 2)); B := StrToInt('$' + Copy(AValue, 7, 2)); Result := MakeColor(A, R, G, B); end; What am I doing wrong?

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  • C++: defining maximum/minimum limits for a class

    - by Luis
    Basically what the title says... I have created a class that models time slots in a variable-granularity daily schedule (where for example the first time slot is 30 minutes, but the second time slot can be 40 minutes); the first available slot starts at (a value comparable to) 1. What I want to do now is to define somehow the maximum and minimum allowable values that this class takes and I have two practical questions in order to do so: 1.- does it make sense to define absolute minimum and maximum in such a way for a custom class? Or better, does it suffice that a value always compares as lower-than any other possible value of the type, given the class's defined relational operators, to be defined the min? (and analogusly for the max) 2.- assuming the previous question has an answer modeled after "yes" (or "yes but ..."), how do I define such max/min? I know that there is std::numeric_limits<> but from what I read it is intended for "numeric types". Do I interpret that as meaning "represented as a number" or can I make a broader assumption like "represented with numbers" or "having a correspondence to integers"? After all, it would make sense to define the minimum and maximum for a date class, and maybe for a dictionary class, but numeric_limits may not be intended for those uses (I don't have much experience with it). Plus, numeric_limits has a lot of extra members and information that I don't know what to make with. If I don't use numeric_limits, what other well-known / widely-used mechanism does C++ offer to indicate the available range of values for a class?

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  • Using an IN clause in Vb.net to save something to the database using SQL

    - by Rob
    I have a textbox and a button on a form. I wish to run a query (in Vb.Net) that will produce a query with the IN Values. Below is an example of my code myConnection = New SqlConnection("Data Source=sqldb\;Initial Catalog=Rec;Integrated Security=True") myConnection.Open() myCommand = New SqlCommand("UPDATE dbo.Recordings SET Status = 0 where RecID in ('" & txtRecID.Text & "') ", myConnection) ra = myCommand.ExecuteNonQuery() myConnection.Close() MsgBox("Done!", _ MsgBoxStyle.Information, "Done") When I enter a single value it works but when I enter values with commas it throws an error: "Conversion failed when converting the varchar value '1234,4567' to data type int." Could someone please help me to solve this or if there is an alternative way? Many Thanks

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  • Does anyone know of a way to easily convert a PDF to a docx format programmatically

    - by Rob
    We have a couple 3rd party systems that give us PDFs. We would like to convert those PDFs for display on the web without using an Adobe product. Ideally we would like to use Silverlight to render the PDFs but are having trouble converting from a PDF to Xaml or using docx format as a middle man. There are lots of libraries that give PDFs but that is not what we need. If there is a library out there that does this, a .net lib would be preferable but we can run the conversion using the command line as well if that is an option.

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  • non-scalar type requested

    - by lego69
    can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); virtual ~A(){}; virtual void foo(); void foo() const; operator int(); }; class B: public A { public: B(int initPlayer): A(initPlayer){}; ~B(){}; virtual void foo(); };

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  • Can I assume Flash and PHP will generate the same floating point numbers?

    - by Fragsworth
    In a multiplayer game I'm developing, we have a few values that are floating point numbers. The back-end (in PHP) and the front-end (in Flash) occasionally perform the same calculations on these numbers, to minimize communication. I am currently making sure that both sides are using 64-bit doubles, but am I safe to assume that all calculations will be the same? For instance, what about string to float conversion - should I worry about Flash having a potentially different implementation as PHP? (If this happens, our game will go out of sync - the client will think it is in one state while the server is in another) With some testing, it appears to be the same, but I'm just not sure. Can someone clarify this for me?

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  • Send and receive data trough the power network

    - by luvieere
    I'm not interested in a hardware solution, I want to know about software that may "read" modulated signal received trough the power supply - some sort of a low-level driver that would access the power signal in a convenient place and demodulate it. Is there a way to receive signal from the computer's power supply? I'm interested in an API or library that would allow the computer to be seen as a node in a Power Line Communication network and receive data directly through the power cable, without the need for a converter. Is there any active research in this field? Edit: There is software that reads monitors and displays internal component voltages - DC voltage after being converted and filtered by the power supply - now I need is a method of data encoding that would be invariant to conversion and filtering, the original signal embedded in AC being present in some form within the converted DC signal.

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  • return char1 + char2? Isn't it possible?

    - by pocoa
    I'm trying to return a string from a function. Which basically adds some chars together and return the string representation. string toString() { char c1, c2, c3; // some code here return c1 + c2; // Error: invalid conversion from `char' to `const char*' } it is possible to return boolean values like return c1 == 'x'. Isn't it possible to return string values? I know that it is possible to it like this: string result; result.append(c1, c2); return result; I'm new to C++ so I thought that there must be more elegant solution around.

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  • How to search for a string including spaces in Objective C?

    - by AlexCu
    I have a real basic command-line program, in Objective-C, that searches for user inputed information. Unfourtunately, the code will only read the first word in series of words that the user enters. For example, if the user enters in "Apples are great", only "Apples" is kept (and hence searched later on), excluding the "are great" part of the sentence. Here's what I have so far: char enteredQuery [128]; // array 'name' to hold the scanf string NSString *searchQuery; // ending NSString to hold and compare the user inputed data NSLog(@"Enter search query:"); scanf("%s", enteredQuery); //will read the next line searchQuery = [NSString stringWithCString: enteredQuery encoding: NSASCIIStringEncoding]; //converts scanf data into a NSString type I know it's got to do with me using scanf or the character-encoder conversion, but I can't seem to figure it out. Any help in solving the problem is very appreciated! Thanks.

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  • Goldbach theory in C

    - by nofe
    I want to write some code which takes any positive, even number (greater than 2) and gives me the smallest pair of primes that sum up to this number. I need this program to handle any integer up to 9 digits long. My aim is to make something that looks like this: Please enter a positive even integer ( greater than 2 ) : 10 The first primes adding : 3+7=10. Please enter a positive even integer ( greater than 2 ) : 160 The first primes adding : 3+157=160. Please enter a positive even integer ( greater than 2 ) : 18456 The first primes adding : 5+18451=18456. I don't want to use any library besides stdio.h. I don't want to use arrays, strings, or anything besides for the most basic toolbox: scanf, printf, for, while, do-while, if, else if, break, continue, and the basic operators (<,, ==, =+, !=, %, *, /, etc...). Please no other functions especially is_prime. I know how to limit the input to my needs so that it loops until given a valid entry. So now I'm trying to figure out the algorithm. I thought of starting a while loop like something like this: #include <stdio.h> long first, second, sum, goldbach, min; long a,b,i,k; //indices int main (){ while (1){ printf("Please enter a positive integer :\n"); scanf("%ld",&goldbach); if ((goldbach>2)&&((goldbach%2)==0)) break; else printf("Wrong input, "); } while (sum!=goldbach){ for (a=3;a<goldbach;a=(a+2)) for (i=2;(goldbach-a)%i;i++) first = a; for (b=5;b<goldbach;b=(b+2)) for (k=2;(goldbach-b)%k;k++) sum = first + second; } }

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  • Workaround for UnsupportedAudioFileException ?

    - by tschan
    I'm in a very early stage of writing a small music/rhythm game in Java (via Slick framework, which in turns uses OpenAL, but that's probably irrelevant here). The game needs to read (and playback) several sound files in WAV format, but some of the files are throwing [javax.sound.sampled.UnsupportedAudioFileException] exceptions. at javax.sound.sampled.AudioSystem.getAudioInputStream(AudioSystem.java:1102) at org.newdawn.slick.openal.WaveData.create(WaveData.java:123) at org.newdawn.slick.openal.SoundStore.getWAV(SoundStore.java:713) at org.newdawn.slick.openal.SoundStore.getWAV(SoundStore.java:683) at org.newdawn.slick.Sound.<init>(Sound.java:33) The files can be played back just fine in Winamp or Foobar2000, so this means Java just don't recognize some variants of the file format. What are my options at this point? Note: The files in question are user-supplied, so i cannot just convert them beforehand (using something like audacity). Any conversion steps must be done at runtime.

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  • How to support comparisons for QVariant objects containing a custom type?

    - by Tyler McHenry
    According to the Qt documentation, QVariant::operator== does not work as one might expect if the variant contains a custom type: bool QVariant::operator== ( const QVariant & v ) const Compares this QVariant with v and returns true if they are equal; otherwise returns false. In the case of custom types, their equalness operators are not called. Instead the values' addresses are compared. How are you supposed to get this to behave meaningfully for your custom types? In my case, I'm storing an enumerated value in a QVariant, e.g. In a header: enum MyEnum { Foo, Bar }; Q_DECLARE_METATYPE(MyEnum); Somewhere in a function: QVariant var1 = QVariant::fromValue<MyEnum>(Foo); QVariant var2 = QVariant::fromValue<MyEnum>(Foo); assert(var1 == var2); // Fails! What do I need to do differently in order for this assertion to be true? I understand why it's not working -- each variant is storing a separate copy of the enumerated value, so they have different addresses. I want to know how I can change my approach to storing these values in variants so that either this is not an issue, or so that they do both reference the same underlying variable. It don't think it's possible for me to get around needing equality comparisons to work. The context is that I am using this enumeration as the UserData in items in a QComboBox and I want to be able to use QComboBox::findData to locate the item index corresponding to a particular enumerated value.

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  • C++ enumaration

    - by asli
    Hi,my question is about enumaration,my codes are : #include<iostream> using namespace std; int main() { enum bolumler{programcilik,donanim,muhasebe,motor,buro} bolum; bolum = donanim; cout<<bolum<<endl; bolum+=2; /* bolum=motor */ cout<<bolum; return 0; } The output should be 1 3 but according to these codes the error is: error C2676: binary '+=' : 'enum main::bolumler' does not define this operator or a conversion to a type acceptable to the predefined operator Error executing cl.exe. 111.obj - 1 error(s), 0 warning(s) Can you help me ?The other question is what can I do if I want to see the output like that "muhasebe"?

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  • C programming - How to print numbers with a decimal component using only loops?

    - by californiagrown
    I'm currently taking a basic intro to C programming class, and for our current assignment I am to write a program to convert the number of kilometers to miles using loops--no if-else, switch statements, or any other construct we haven't learned yet are allowed. So basically we can only use loops and some operators. The program will generate three identical tables (starting from 1 kilometer through the input value) for one number input using the while loop for the first set of calculations, the for loop for the second, and the do loop for the third. I've written the entire program, however I'm having a bit of a problem with getting it to recognize an input with a decimal component. Here is what I have for the while loop conversions: #include <stdio.h> #define KM_TO_MILE .62 main (void) { double km, mi, count; printf ("This program converts kilometers to miles.\n"); do { printf ("\nEnter a positive non-zero number"); printf (" of kilometers of the race: "); scanf ("%lf", &km); getchar(); }while (km <= 1); printf ("\n KILOMETERS MILES (while loop)\n"); printf (" ========== =====\n"); count = 1; while (count <= km) { mi = KM_TO_MILE * count; printf ("%8.3lf %14.3lf\n", count, mi); ++count; } getchar(); } The code reads in and converts integers fine, but because the increment only increases by 1 it won't print a number with a decimal component (e.g. 3.2, 22.6, etc.). Can someone point me in the right direction on this? I'd really appreciate any help! :)

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  • How to extract data from F# list

    - by David White
    Following up my previous question, I'm slowly getting the hang of FParsec (though I do find it particularly hard to grok). My next newbie F# question is, how do I extract data from the list the parser creates? For example, I loaded the sample code from the previous question into a module called Parser.fs, and added a very simple unit test in a separate module (with the appropriate references). I'm using XUnit: open Xunit [<Fact>] let Parse_1_ShouldReturnListContaining1 () = let interim = Parser.parse("1") Assert.False(List.isEmpty(interim)) let head = interim.Head // I realise that I have only one item in the list this time Assert.Equal("1", ???) Interactively, when I execute parse "1" the response is: val it : Element list = [Number "1"] and by tweaking the list of valid operators, I can run parse "1+1" to get: val it : Element list = [Number "1"; Operator "+"; Number "1"] What do I need to put in place of my ??? in the snippet above? And how do I check that it is a Number, rather than an Operator, etc.?

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  • Why is forwarding variadic parameters invalid?

    - by awesomeyi
    Consider the variadic function parameter: func foo(bar:Int...) -> () { } Here foo can accept multiple arguments, eg foo(5,4). I am curious about the type of Int... and its supported operations. For example, why is this invalid? func foo2(bar2:Int...) -> () { foo(bar2); } Gives a error: Could not find an overload for '_conversion' that accepts the supplied arguments Why is forwarding variadic parameters invalid? What is the "conversion" the compiler is complaining about?

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  • how to convert webpage apostrophe (&#8217;) to ascii 39 in ruby 1.8.7

    - by maninwarren
    That's pretty much it. I'm using Nokogiri to scrape a web page what has ’ ; characters in it, and I can't figure out how to do the conversion. here's what I tried: str.gsub(/&#8217;/,"'") str.gsub("&#8217;","'") str.gsub("GÇÖ","'") # that's how it looks when I do a puts (In the above, there's no space between the ’ and the ";", but if I don't put the space in, SO converts it to an apostrophe -- the cruel, cruel irony!) I'm sure this is covered somewhere, but couldn't find the solution here or on the web. TIA

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  • Dynamic Object Not Creating for Privately Inherited Class.

    - by mahesh
    Hi, What is the reason for the following code that does not let me to create object. class base { public: void foo() { cout << "base::foo()"; } }; class derived : private base { public: void foo() { cout << "deived::foo()"; } }; void main() { base *d = new derived(); d->foo(); } It Gives me error : " 'type cast' : conversion from 'derived *' to 'base *' exists, but is inaccessible" Thanks in advance :)

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  • Quick, Beginner C++ Overloading Question - Getting the compiler to perceive << is defined for a spec

    - by Francisco P.
    Hello everyone. I edited a post of mine so I coul I overloaded << for a class, Score (defined in score.h), in score.cpp. ostream& operator<< (ostream & os, const Score & right) { os << right.getPoints() << " " << right.scoreGetName(); return os; } (getPoints fetches an int attribute, getName a string one) I get this compiling error for a test in main(), contained in main.cpp binary '<<' : no operator found which takes a right-hand operand of type 'Score' (or there is no acceptable conversion) How come the compiler doesn't 'recognize' that overload as valid? (includes are proper) Thanks for your time.

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  • How to call/use a value converter inverted

    - by Soko
    Is it possible to use a converter the "wrong" way around? In other words: can I swap source and target? Here's an example: I created a simple IValueConverter called NullableDecimalToStringConverter which converts an input if "" into null and a number into decimal. I use it to bind a TextBox in my WPF view to a decimal? property in my ViewModel. In another context I'd like to convert a NullableDecimal into a String in the same way... Is it possible to simply use the existing NullableDecimalToStringConverter inverted? One method is to use the parameter of the converter to tell the converter which way it should convert. But is there a .NET build in way to do such a thing? Another way would be to build a base class with both conversion methods and two separate converter which call the base class methods...

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