why do I see a compile time error for the below?

Question

I'm trying to do a simple program, adding a node to the end of the link list:

/*Insert Node at the end of a linked list 

  head pointer input could be NULL as well for empty list



Node is defined as 

  struct Node

  {

     int data;

     struct Node *next;

  }

*/



Node* Insert(Node *head,int data)

{



    if(head){

         Node *curr_node=head;



        while(curr_node->next)

            curr_node=curr_node->next;

    }



    Node *new_node=(Node *)calloc(1,sizeof(Node));

    new_node->data=data;

    new_node->next=NULL;



    if(head)

            curr_node->next=new_node;

    else

            head=new_node;



    return head;

}



/* the main function calls it*/

when I compile, I see the following error:

In function ‘Node* Insert(Node*, int)’:
solution.cc:59:13: error: ‘curr_node’ was not declared in this scope
curr_node->next=new_node

why does it say curr_node not declared, when it's actually declared right in the beginning. What am I missing here?

Answer 1

A variable declared in a function definition has a scope which extends only to the innermost {} braces. So your variable curr_node is no longer valid after the first if block.

To fix this, declare your variable outside the if block:

Node* Insert(Node *head,int data)
{
    Node *curr_node = NULL;
    if(head){
        curr_node=head;

        while(curr_node->next)
            curr_node=curr_node->next;
    }

why do I see a compile time error for the below?

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