Self Referencing (in a way)

This is a discussion on Self Referencing (in a way) within the C++ Programming forums, part of the General Programming Boards category; Suppose in a class, I'd like to assign the address of the variable of that class type to a global ...

  1. #1
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    Self Referencing (in a way)

    Suppose in a class, I'd like to assign the address of the variable of that class type to a global variable, during construction. I don't know if this is possible, but it should, considering the address of the variable has already been assigned.

    Something like:
    Code:
    class() {
       globalvarptr = &(self?);
    }

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    this, not self. And since this is a pointer already, no need to take its address.

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    I didn't understand that. There's a variable lets say 'a', which is off this class. While 'a' is being constructed, i'd like to the ptr to reference the address of a.

  4. #4
    CSharpener vart's Avatar
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    Inside any function of the class (including constructor and destructor) you can use pointer "this" to access the currect instance of the class
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  5. #5
    Registered User Tonto's Avatar
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    Code:
    class little_bunny { little_bunny * foo_foo; little_bunny() : foo_foo(this) { hoppin_thru_da_forest(); } void hoppin_thru_da_forest() { std::cout << "hoppin_thru_da_forest"; } };

    ╔╗╔╦══╦╗╔╦══╦╗
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    codez http://code.google.com/p/zxcvbn/

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    Thanks, That's all I wanted.

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    Ok, I'm having another problem. The pointer that I'm going to reference to 'this' must be defined to be a 'class'. But that means that I'd have to put the class def infront of it. But the class includes this variable (globalvarptr), so it must be put before the class definition. How do I get out of this fix?

  8. #8
    CSharpener vart's Avatar
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    The pointer that I'm going to reference to 'this' must be defined to be a 'class'.
    Must be defined as pointer to the class... you can do it before actual class definition
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    Here's the code I used:
    Code:
    #include <iostream>
    using namespace std;
    
    ape* aptr;
    
    class ape
    {
    public:
    	ape(){
    		aptr =  this;
    	}
    	~ape(){}
    };
    
    
    int main()
    {
    
    	ape a;
    	cout << &a << " " << aptr;
    	return 0;
    }
    The complier errors are:
    1>d:\visual studio 2005\projects\test\test.cpp(4) : error C2143: syntax error : missing ';' before '*'
    1>d:\visual studio 2005\projects\test\test.cpp(4) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    1>d:\visual studio 2005\projects\test\test.cpp(4) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
    1>d:\visual studio 2005\projects\test\test.cpp(10) : error C2440: '=' : cannot convert from 'ape *const ' to 'int *'
    1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
    1>d:\visual studio 2005\projects\test\test.cpp(19) : error C2146: syntax error : missing ';' before identifier 'a'
    1>d:\visual studio 2005\projects\test\test.cpp(19) : error C2065: 'a' : undeclared identifier
    I use the VC++ Express.

  10. #10
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    Oh, and another doubt, is there any call to output the type of the variable. Python has something like: type(variable), which outputs the type.

  11. #11
    CSharpener vart's Avatar
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    Quote Originally Posted by studiesrule
    Code:
    ape* aptr;
    try
    Code:
    class ape* aptr;
    instead
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    worked like a charm. Thanks for your persistent help.

  13. #13
    CSharpener vart's Avatar
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    don't forget to initialize the pointer to NULL to avoid using uninitialized pointer before the first instance of the class is created

    Don't forget to reset the pointer to NULL when the last instance is destructed.

    Don't forget to check that the pointer is not Null before using it...
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  14. #14
    semi-colon generator ChaosEngine's Avatar
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    Quote Originally Posted by vart
    don't forget to initialize the pointer to NULL to avoid using uninitialized pointer before the first instance of the class is created

    Don't forget to reset the pointer to NULL when the last instance is destructed.

    Don't forget to check that the pointer is not Null before using it...
    IOW use a smart pointer...
    "I saw a sign that said 'Drink Canada Dry', so I started"
    -- Brendan Behan

    Free Compiler: Visual C++ 2005 Express
    If you program in C++, you need Boost. You should also know how to use the Standard Library (STL). Want to make games? After reading this, I don't like WxWidgets anymore. Want to add some scripting to your App?

  15. #15
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    When you compile, check the intermediate assembler code. There is probably NO TRACE that you had EVER used classes at all. If you want get-instance-type sugary stuff, stick to Python.
    Code:
    #include <stdio.h>
    
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

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