How can I declare a structure in C++ without defining it? -

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i have been following tutorial @ cplusplus.com/doc/tutorial. near end of functions page, discussed prototyping function. later on, read structures. thought looked little messy, , code blocks after main method. wondered if prototype data structure. tried this:

#include <iostream> using namespace std;  struct astruct;  int main() {      astruct structure;      structure.a = 1;     structure.b = 2;      cout << structure.a << ", " << structure.b << "\n";      return 0; }  struct astruct {     int a;     int b; };

but ide said "astruct not declared in scope". so, how prototype data structure bulk of can below main method?

the tutorial pages: functions data strucutres

generally reason pre-declaring structure avoiding circular references in defining structures. right solution use header, , hide structure definition in header instead:

inside astruct.h:

struct astruct {   int a;   int b; };

inside main.cpp:

#include <iostream> #include "astruct.h" using namespace std;  struct astruct;  int main() {      astruct structure;      structure.a = 1;     structure.b = 2;      cout << structure.a << ", " << structure.b << "\n";      return 0; }

in long run happier organizing code separate files.

i leave exercise reader protect against multiple inclusion of header using #ifdef astruct_h/#define astruct_h/#endif lines.


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