variable undeclared, first use in this function!

[aashcool198]

#include<iostream>

using namespace std;

struct state {
       int M_count;
       int C_count;
       int boat;
       struct state* parent;
       int Gscore;
       };
       
       
struct openlist {
       struct state obj;
       struct openlist* next;
       };
       
struct closedlist {

       struct state obj;
       struct closedlist* next;       
       
       };

struct openlist* tail_open = NULL;
struct closedlist* tail_closed = NULL;

struct state move_mc(struct state st){
       
       struct state temp = st;
       if (temp.boat==0){
       temp.boat=1;
       temp.C_count = temp.C_count -1; 
       temp.M_count = temp.M_count -1;  
       temp.*parent = st;
       temp.Gscore++;                
       }
       if (temp.boat==1){
       temp.boat=0;
       temp.C_count = temp.C_count +1; 
       temp.M_count = temp.M_count +1;  
       temp.*parent = st;
       temp.Gscore++;                
       }
       return temp;
       }

This is a peice of my code. The error says:

  
In function `state move_mc(state)':
`parent' undeclared (first use this function)  

please help!

[bluecoder]

there is no need of keyword struct in the line 29

[imi]

there is no need of keyword struct in the line 29

That's right but not the problem.

(Putting the "struct" before some struct in C++ is optional - unlike C. It forward-declares the struct "in place". You can declare a stuct as many times as you want. "state" is already defined in line 5, so it's a useless forward declaration.)


The problem at hand here is the typo in line 36 and 43. temp.*parent should most probably be *temp.parent. You want to assign "st" to the place where "temp.parent" points to, right?


(For an interpretation of the error message: There is an operator.*() in C++. It's calling an member function pointer. Your compiler thinks when reading "temp.*parent" that you are going to call a member function pointer to the function stored in the local variable "parent" using "temp" as a this-object. But you don't have any "parent" in current scope, hence the strange looking error.)

[bluecoder]

_{(Putting the "struct" before some struct in C++ is optional - unlike C. It forward-declares the struct "in place". You can declare a stuct as many times as you want. "state" is already defined in line 5, so it's a useless forward declaration.)}


Thanks for letting me know about the struct imi .