Singly linked list of structs

[oudavid1]

Hey everyone, I want to make a singly linked list of structs with a custom datatype. Sadly, I dont think I understand either.

#include <iostream>
using namespace std;

struct datatype
	{
		string name;
		int id;
		float amt;
	};
struct Node
{
	datatype data;
	Node *next;
}*node;

class List 
{
	Node *head;
public:
			void insert(int);
			void remove();
			List(){head = 0;}
};

void List::insert(int){
	
}

int main ()
{

}

Basically, I cant figure out how to insert a strcut with a string, random ID number, and a random salary amount, into a linked list.

Any suggestions?

[ingenioushax]

In order to access elements of your "datatype" struct using your node struct, you're going to have to use some syntax similar to this:

node->data->name="name";
node->data->id=10023923;
node->data->amt=1200.00;

[D80DSL3A]

You will want void insert(datatype); since you would be inserting that type (not ints).
A constructor for the datatype struct would be helpful:
datatype(string Name, int Id, float Amt): name(Name), id(Id), amt(Amt) {}

Then, generate the values for Name, Id and Amt (random values if you wish) then call
insert( datatype(Name,Id,Amt) ); to add it to the list.

[oudavid1]

fun2Code, im confused, where would I put the datatype constructor?

[D80DSL3A]

In the definition of the datatype struct, like so:

struct datatype
	{
		string name;
		int id;
		float amt;
                datatype(string Name, int Id, float Amt): name(Name), id(Id), amt(Amt) {}
                datatype(void): name(""), id(0), amt(0.0f) {}// no argument ctor
	};

I added a no-arg constructor so it is still possible to declare a datatype without supplying any parameters, as in:
datatype a; or datatype arr[5];

[oudavid1]

Ok, here is my class and insert method, it is giving me error on the variables not being available. I thought everything in a struct was globally available?

class List 
{
	Node *head;
public:
			void insert(datatype);
			void remove();
			List(){head = 0;}
};

void List::insert( datatype(Name,Id,Amt) );
	if (head == NULL){
		
		}
}

[D80DSL3A]

It is, but your code has a few syntax problems.
This may work better, though it isn't inserting anything yet:

void List::insert( datatype dat )
{
    if( head== NULL )
    {
       // list is empty. Create the head node.
    }
    else
    {
       // add a node to the list
    }
}

[oudavid1]

Ok, I see how you referenced the variable, now how do you insert the 3 different datatypes of the actual struct?

[D80DSL3A]

It's easiest to insert at the front of the list:

void List::insert( datatype dat )
{
    Node* temp = new Node;
    temp->data = dat;// all 3 datatype members will be copied here
    temp->next = head;// the last Node added becomes second in the list
    head = temp;// the newly added Node is now the first one in the list
}

Example of usage in main():

int main()
{
    List myList;// declare an empty list
    myList.insert( datatype("Jack", 123, 20.45f) );// insert 1st node

    return 0;
}

[oudavid1]

int main()
{
    List myList;// declare an empty list
    myList.insert( datatype("Jack", 123, 20.45f) );// insert 1st node

    return 0;
}

This was the part I was confused on. But it makes sense now. Thank you so much for taking the time.

[oudavid1]

When I use the code in my main() function, it tells me that datatype is undefined. Is that because the computer executes the main() code first? How do I declare it since it is a struct?

[LB]

In the cpp file with main, make sure you included the header that declares datatype.

[oudavid1]

Is that the only way to make it work? I'm not too good with header files....

[LB]

#include "MyHeaderFile.hpp"

int main()
{
    //blah
}

[oudavid1]

so in the main() in the header "MyHeaderFile.hpp" I would declare the struct called datatype?

[LB]

If you wanted to use headers, yes.

If you look at your first post though, you can just define everything before main, but it is conventional to properly use headers.

[oudavid1]

Well i thought I did have everything defined before the main(). I have the struct defined first. Without using a header, can you show me what it would look like?

[LB]

struct MyStruct
{
    //blah
};

int main()
{
    //blah
}

Maybe you should post your entire program so we can see what is wrong?

[oudavid1]

#include <iostream>
using namespace std;

struct datatype
	{
		string name;
		int id;
		float amt;
	}node;
struct Node
{
	datatype data;
	Node *next;
}*node;

class List 
{
	Node *head;
public:
			void insert(datatype dat);
			void remove();
			List(){head = 0;}
};

void List::insert(datatype dat){
	{
    Node* temp = new Node;
    temp->data = dat;
    temp->next = head;
    head = temp;
}

}

int main ()
{
	 List myList;
	 myList.insert(datatype[***Error is here, says this is undefined]("Jack", 123, 20.45f));

    return 0;
}

Here it is. I pointed out the one error I keep getting flagged for.

[LB]

Remove "node" and "*node" from lines 9 and 14

The problem is that you didn't add the constructor to datatype like fun2code told you to:
http://www.cplusplus.com/forum/general/94267/#msg506159