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  • How do I find out if the variable is declared in Python?

    - by golergka
    I want to use a module as a singleton referenced in other modules. It looks something like this (that's not actually a code I'm working on, but I simplified it to throw away all unrelated stuff): main.py import singleton import printer def main(): singleton.Init(1,2) printer.Print() if __name__ == '__main__': pass singleton.py variable1 = '' variable2 = '' def Init(var1, var2) variable1 = var1 variable2 = var2 printer.py import singleton def Print() print singleton.variable1 print singleton.variable2 I expect to get output 1/2, but instead get empty space. I understand that after I imported singleton to the print.py module the variables got initialized again. So I think that I must check if they were intialized before in singleton.py: if not (variable1): variable1 = '' if not (variable2) variable2 = '' But I don't know how to do that. Or there is a better way to use singleton modules in python that I'm not aware of :)

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  • initialising a 2-dim Array in Scala

    - by Stefan W.
    (Scala 2.7.7:) I don't get used to 2d-Arrays. Arrays are mutable, but how do I specify a 2d-Array which is - let's say of size 3x4. The dimension (2D) is fixed, but the size per dimension shall be initializable. I tried this: class Field (val rows: Int, val cols: Int, sc: java.util.Scanner) { var field = new Array [Char](rows)(cols) for (r <- (1 to rows)) { val line = sc.nextLine () val spl = line.split (" ") field (r) = spl.map (_.charAt (0)) } def put (val rows: Int, val cols: Int, c: Char) = todo () } I get this error: :11: error: value update is not a member of Char field (r) = spl.map (_.charAt (0)) If it would be Java, it would be much more code, but I would know how to do it, so I show what I mean: public class Field { private char[][] field; public Field (int rows, int cols, java.util.Scanner sc) { field = new char [rows][cols]; for (int r = 0; r < rows; ++r) { String line = sc.nextLine (); String[] spl = line.split (" "); for (int c = 0; c < cols; ++c) field [r][c] = spl[c].charAt (0); } } public static void main (String args[]) { new Field (3, 4, new java.util.Scanner ("fraese.fld")); } } and fraese.fld would look, for example, like that: M M M M . M I get some steps wide with val field = new Array Array [Char] but how would I then implement 'put'? Or is there a better way to implement the 2D-Array. Yes, I could use a one-dim-Array, and work with put (y, x, c) = field (y * width + x) = c but I would prefer a notation which looks more 2d-ish.

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  • C++: Unknown pointer size when forward declaring (error C2036)

    - by Rosarch
    In a header file, I have forward declared two members of a namespace: namespace Foo { struct Odp typedef std::vector<Odp> ODPVEC; }; class Bar { public: Foo::ODPVEC baz; // C2036 }; The error generated by the compiler is: error C2036: 'Foo::Odp *': unknown size I'm guessing this is an issue with forward declaring Odp. How can I get around this?

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  • mixed declarations and codes

    - by gcc
    When I compile function with "gcc -o dene -Wall -ansi -pedantic-errors dene.c",gcc emits no error.(can you look a line which starts with char ....,in if loop,) static void remove_negation(char *s,char *s1) { char **cmainp=malloc(sizeof(char*)*1); int len=0;int d=0; int i=0; cmainp[0]=malloc(sizeof(char)*300); len=strlen(s); for(i=0;i<len;++i) { if(s[i]=='-') if(i==0 || s[i-1]==',') /*look*/ {char *p=malloc(sizeof(char)*3); /*look*/ ++i; p[0]=s[i]; p[1]='\0'; strcat(s1,","); strcat(s1,p); free(p); continue; } cmainp[0][d]=s[i]; ++d; } cmainp[0][d+1]='\0'; strcpy(cmainp[0],s); free(cmainp[0]); } But,when compile above function being reformatted with gcc,gcc emits that error "dene.c:10: error: ISO C90 forbids mixed declarations and code" static void remove_negation(char *s,char *s1) { char **cmainp=malloc(sizeof(char*)*1); /*look*/ cmainp[0]=malloc(sizeof(char)*300); /*look*/ int len=0;int d=0; int i=0; len=strlen(s); for(i=0;i<len;++i) { if(s[i]=='-') if(i==0 || s[i-1]==',') {char *p=malloc(sizeof(char)*3); ++i; p[0]=s[i]; p[1]='\0'; strcat(s1,","); strcat(s1,p); free(p); continue; } cmainp[0][d]=s[i]; ++d; } cmainp[0][d+1]='\0'; strcpy(cmainp[0],s); free(cmainp[0]); } And last one,gcc emits following errors dene.c:16: error: expected expression before ‘char’ dene.c:20: error: ‘p1’ undeclared (first use in this function) dene.c:20: error: (Each undeclared identifier is reported only once dene.c:20: error: for each function it appears in.) static void remove_negation(char *s,char *s1) { char **cmainp=malloc(sizeof(char*)*1); /*look*/ cmainp[0]=malloc(sizeof(char)*300); /*look*/ int len=0;int d=0; int i=0; len=strlen(s); for(i=0;i<len;++i) { if(s[i]=='-') /*look*/ char *p=malloc(sizeof(char)*3); /*look*/ if(i==0 || s[i-1]==',') { ++i; p[0]=s[i]; p[1]='\0'; strcat(s1,","); strcat(s1,p); free(p); continue; } cmainp[0][d]=s[i]; ++d; } cmainp[0][d+1]='\0'; strcpy(cmainp[0],s); free(cmainp[0]); } question is why there are differences between them.

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  • Is there a standard literal constant that I can use instead of "utf-8" in C# (.Net 3.5)?

    - by Hamish Grubijan
    Hi, I would like to find a better way to do this: XmlNode nodeXML = xmlDoc.AppendChild( xmlDoc.CreateXmlDeclaration( "1.0", "utf-8", String.Empty) ); I do not want to think about "utf-8" vs "UTF-8" vs "UTF8" vs "utf8" as I type code. I would like to make my code less prone to typos. I am sure that some standard library has declatred "utf-8" as a const / readonly string. How can I find it? Also, what about "1.0"? I am assuming that major XML versions have been enumerated somewhere as well. Thanks!

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  • How can I declare a pointer structure?

    - by Y_Y
    This probably is one of the easiest questions ever in C programming language... I have the following code: typedef struct node { int data; struct node * after; struct node * before; }node; struct node head = {10,&head,&head}; Is there a way I can make head to be *head [make it a pointer] and still have the availability to use '{ }' [{10,&head,&head}] to declare an instance of head?

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  • How to use two parameters pointing to the same structure in one function ?

    - by ZaZu
    Hey guys, I have my code below that consits of a structure, a main, and a function. The function is supposed to display two parameters that have certain values, both of which point to the same structure. The problem I dont know how to add the SECOND parameter onto the following code : #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; for(i=0;i<5;i++){ printf("%f,(*test).what[z][x]); } return 0; } I need to add a new parameter test_2 there (IN THE SAME FUNCTION) using this code : for(i=0;i<5;i++){ printf("%f,(*test_2).what[z][x]); How does int trialtest(trial *test) changes ? and how does it change in main ? I know that I should declare test_2 as well, like this : trial test,test_2; But what about passing the address in the function ? I do not need to edit it right ? trialtest(&test); --- This will remain the same ? So please, tell me how would I use test_2 as a parameter pointing to the same structure as test, both in the same function.. Thank you !! Please tell me if you need more clarification

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  • Mixed declarations and code in open source projects?

    - by Eduardo
    Why is still C99 mixed declarations and code not used in open source C projects like the Linux kernel or GNOME? I really like mixed declarations and code since it makes the code more readable and prevents hard to see bugs by restricting the scope of the variables to the narrowest possible. This is recommended by Google for C++. For example, Linux requires at least GCC 3.2 and GCC 3.1 has support for C99 mixed declarations and code

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  • Why are forward declarations necessary?

    - by user199421
    In languages like C# and Java there is no need to declare (for example) a class before using it. If I understand it correctly this is because the compiler does two passes on the code. In the first it just "collects the information available" and in the second one it checks that the code is correct. In C and C++ the compiler does only one pass so everything needs to be available at that time. So my question basically is why isn't it done this way in C and C++. Wouldn't it eliminate the needs for header files?

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  • Any way in C++ to forward declare a function prototype?

    - by jsyjr
    I make regular use of forward class declarations and pointers to such classes. I now have a need to pass a function pointer through a number of layers. I would prefer to include the header that declares my function pointer's prototype only into the module that dereferences a function pointer rather than into each layer that simply passes along that pointer value. Is this possible?

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  • C99 mixed declarations and code in open source projects?

    - by Eduardo
    Why is still C99 mixed declarations and code not used in open source C projects like the Linux kernel or GNOME? I really like mixed declarations and code since it makes the code more readable and prevents hard to see bugs by restricting the scope of the variables to the narrowest possible. This is recommended by Google for C++. For example, Linux requires at least GCC 3.2 and GCC 3.1 has support for C99 mixed declarations and code

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  • C++ Why am I unable to use an enum declared globally outside of the class it was declared in?

    - by VGambit
    Right now, my project has two classes and a main. Since the two classes inherit from each other, they are both using forward declarations. In the first object, right underneath the #include statement, I initialize two enums, before the class definition. I can use both enums just fine inside that class. However, if I try to use those enums in the other class, which inherits from the first one, I get an error saying the enum has not been declared. If I try to redefine the enum in the second class, I get a redefinition error. I have even tried using a trick I just read about, and putting each enum in its own namespace; that didn't change anything.

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  • typedef struct, circular dependency, forward definitions

    - by BlueChip
    The problem I have is a circular dependency issue in C header files ...Having looked around I suspect the solution will have something to do with Forward Definitions, but although there are many similar problems listed, none seem to offer the information I require to resolve this one... I have the following 5 source files: // fwd1.h #ifndef __FWD1_H #define __FWD1_H #include "fwd2.h" typedef struct Fwd1 { Fwd2 *f; } Fwd1; void fwd1 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD1_H . // fwd1.c #include "fwd1.h" #include "fwd2.h" void fwd1 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwd2.h #ifndef __FWD2_H #define __FWD2_H #include "fwd1.h" typedef struct Fwd2 { Fwd1 *f; } Fwd2; void fwd2 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD2_H . // fwd2.c #include "fwd1.h" #include "fwd2.h" void fwd2 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwdMain.c #include "fwd1.h" #include "fwd2.h" int main (int argc, char** argv, char** env) { Fwd1 *f1 = (Fwd1*)0; Fwd2 *f2 = (Fwd2*)0; fwd1(f1, f2); fwd2(f1, f2); return 0; } Which I am compiling with the command: gcc fwdMain.c fwd1.c fwd2.c -o fwd -Wall I have tried several ideas to resolve the compile errors, but have only managed to replace the errors with other errors ...How do I resolve the circular dependency issue with the least changes to my code? ...Ideally, as a matter of coding style, I would like to avoid putting the word "struct" all over my code.

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  • C++ - defining static const integer members in class definition

    - by HighCommander4
    My understanding is that C++ allows static const members to be defined inside a class so long as it's an integer type. Why, then, does the following code give me a linker error? #include <algorithm> #include <iostream> class test { public: static const int N = 10; }; int main() { std::cout << test::N << "\n"; std::min(9, test::N); } The error I get is: test.cpp:(.text+0x130): undefined reference to `test::N' collect2: ld returned 1 exit status Interestingly, if I comment out the call to std::min, the code compiles and links just fine (even though test::N is also referenced on the previous line). Any idea as to what's going on? My compiler is gcc 4.4 on Linux.

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  • MVVM User control - where do i declare it to get data from page ?

    - by Anish
    I have a WPF user control ...which is in MVVM. The user control(which contains a listview) need data from the page (where it is included). I have to set a property in View's code behind to get this data input. Will this comply with MVVM(But MVVM pattern do not support adding code in code behind file of view as far as i know).if not, what is the way for the same?

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  • How can I declare a pointer structure using {}?

    - by Y_Y
    This probably is one of the easiest question ever in C programming language... I have the following code: typedef struct node { int data; struct node * after; struct node * before; }node; struct node head = {10,&head,&head}; Is there a way I can make head to be *head [make it a pointer] and still have the availability to use '{ }' [{10,&head,&head}] to declare an instance of head and still leave it out in the global scope? For example: //not legal!!! struct node *head = {10,&head,&head};

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  • How to declare a pointer to a variable as a parameter of a function in C++?

    - by Keand64
    I have a function that takes a pointer to a D3DXVECTOR3, but I have no reason to declare this beforehand. The most logical solution to me was using new: Function( //other parameters, new D3DXVECTOR3(x, y, 0)); but I don't know how I would go about deleting it, beign intitialized in a function. My next thought was to use the & operator, like so: Function( //other parameters, &D3DVECTOR3(x, y, 0)); but I don't know if this is a valid way to go about doing this. (It doesn't get an error, but neither does int *x; x = 50;). So should I use new, &, or some other technique I'm overlooking?

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  • What is the '@(' doing in this Perl code?

    - by Anthony Veckey
    In this code snippet: use strict; use warnings; use Data::Dumper; my $r = [qw(testing this thing)]; print Dumper($r); foreach my $row (@({$r}) { print "$row\n"; $row .= 'mod'; } print Dumper($r); print Dumper(@({$r}); I figured out that the '(' after the '@' in the foreach is causing this not to loop correctly. I have no idea why this code even works as there is no ending parenthesis. What is this doing? It looks to be creating a new variable on the fly, but shouldn't 'use strict' have fired or something? Please help explain what that '@(' is doing and why it still runs without an ending parenthesis.

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  • C# assign values of array to separate variables in one line

    - by Sarah Vessels
    Can I assign each value in an array to separate variables in one line in C#? Here's an example in Ruby code of what I want: irb(main):001:0> str1, str2 = ["hey", "now"] => ["hey", "now"] irb(main):002:0> str1 => "hey" irb(main):003:0> str2 => "now" I'm not sure if what I'm wanting is possible in C#. Edit: for those suggesting I just assign the strings "hey" and "now" to variables, that's not what I want. Imagine the following: irb(main):004:0> val1, val2 = get_two_values() => ["hey", "now"] irb(main):005:0> val1 => "hey" irb(main):006:0> val2 => "now" Now the fact that the method get_two_values returned strings "hey" and "now" is arbitrary. In fact it could return any two values, they don't even have to be strings.

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