CODEWITHSUNDEEP
cstruct
aycan
aycan

Reputation: 13

expression must have pointer type

I have a problem,the program gives an error like "expression must have pointer type".Can you help me ?

struct stack{
    int i_data;
    char c_data;
    struct stack *next;
}top;

void push_i(struct top *newptr,int info){  

    newptr=(struct top*)malloc(sizeof(top));

    if(newptr!=NULL){
        top->c_data=NULL;
        newptr->i_data=info;
        newptr->next=*top;
        *top=newptr;
    }

Upvotes: 1

Views: 26797

Answers (4)

Erik
Erik

Reputation: 91270

  • You're mixing the type struct stack with the variable top
  • Your top variable isn't a pointer, you can't change what it points at.
  • c_data isn't a pointer, so don't assign NULL to it.
  • You're not using the passed newptr for anything useful - it should be a local variable,.

This may work better:

struct stack{
    int i_data;
    char c_data;
    struct stack *next;
};

...
struct stack * top = NULL; 
...
void push_i(int info){  

    struct stack * newptr=(struct stack*)malloc(sizeof(struct stack));

    if(newptr!=NULL){
        top->c_data=0;
        newptr->i_data=info;
        newptr->next=top;
        top=newptr;
    }

Upvotes: 2

PAntoine
PAntoine

Reputation: 689

You have several problems. The 1st is you are using the type top rather than the variable newptr.

Also you might want to be using **newptr when passing the variable in.

Upvotes: 0

Angelom
Angelom

Reputation: 2531

Look at your 'struct stack', thats the description of the structure. Next loop at top, that's an instance of your structure. You appear to be mixing the both. There shouldn't be any 'struct top' anywhere, they should be 'struct stack'.

Upvotes: 0

Ingo
Ingo

Reputation: 36339

newptr->next = top
top = newptr

Remember, if x is declared T*, then x is the pointer, and *x is T. This is really not hard to understand. You want to assign the pointer, not overwrite where the pointer points.

Upvotes: 0

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