Thread: linked lists, strcmp(), char array, & a structure

I'm trying to use information that is stored in a linked list node to compare it to a key. The data in the node is a char array in a structure. The key is a user inputed char array. I want to compare the two for a sort of the linked list. Last name to Last name. It doesn't work. I'm unable to see why it doesn't work.

Below is the code I'm using.

Code:

//prototype 
bool compare(const char*,const char*);

//key declaration
char  Key[SIZE];

//structure definition
struct link                          
{
short age;
short weight;
char fname[SIZE];
char lname[SIZE];
char ssnumber[SIZE];
link *next;                       
};

//my function call
compare(current->lname,Key)

//definition function
bool compare(const char* node,const char* key)
{
	if(strcmp(node,key))
		return true;
	else
		return false;
}

I get the following errors
(1)linked lists error LNK2019: unresolved external symbol "private: bool __thiscall linklist::compare(char const *,char const *)" (?compare@linklist@@AAE_NPBD0@Z) referenced in function "public: void __thiscall linklist::delete_key(void)" (?delete_key@linklist@@QAEXXZ)
(2)linked lists fatal error LNK1120: 1 unresolved externals

strcmp() returns 0 when the strings are equal

So perhaps

Code:

bool compare(const char* node,const char* key)
{
	if(strcmp(node,key) == 0)
		return true;
	else
		return false;
}

No that didn't work.
It says I have unresolved external error.
linking problem. please see the bottom of the prior post for the exact errors.

[Edit]
It is acting as if it will not recognize a bool function call within a void function. Does this even matter?
[\Edit]

I can't see anything wrong with the code you posted there...must be a problem somewhere else ...

It is acting as if it will not recognize a bool function call within a void function. Does this even matter?

I don't see why it would matter...

[edit]
compare(current->lname,Key);
...dont know if that fixes it though
[/edit]

Man, you gotta start being specific about what the actual problem is. You post some code with an obvious flaw, then totally throw a different problem at us.

Try
bool linklist::compare(const char* node,const char* key)

Make it a member function of your class, and not a global function.

I thought I was being specific. I figured it out though.
The issue was created by me thinking I had to create a function that is passed two constant pointers for strcmp() to work.
I recognized that that was not needed. The issues arose from calling the function with passing the linked data and a char key.
I have since then tried to solve the problem without passing to another function and it works perfectly. see the below code. I have a book that states that all string functions like strcmp() needs to have 2 const pointers passed for it to work, but it works with plain pointers with out making them constant. So the book is not correct.

Code:

 
void linklist::delete_key()
{
					
	cout << "Please enter the last name of member you wish to delete: "<<endl;
	cin >> Key;

	int counter=1,keydelete=false;
	char test[SIZE];

	
	if (isempty())
	{
		cout << "Sorry, the list is empty. Nothing to delete." << endl;
		keydelete=false;
	}
	link * current , * previous;
	current = previous = head;
	while (current != NULL)
	{//below here is where I had the function call that was not working. 
		if ( strcmp(current->lname,Key)==0  )
		{
			previous->next = current->next;
			delete current;
			break;
		}
		counter++;
		previous = current;
		current = current->next;
	}

	if (current == NULL)
	{
		cout<<"Key is not in list";
		keydelete=false;
	}
	else
		keydelete=true;			   
	
	if(keydelete)
		cout << "Node key " << Key << " has been deleted.";
}

[edit]
compare(current->lname,Key);
...dont know if that fixes it though
[/edit]

sorry that was just a typo.