Using structures in a linked list

Question

I am trying to create an append_node method to add a node to a linked list I created. My Node structure is defined below:

typedef struct Node{
    struct Node next = NULL;
    int id;
} Node;

However, when compiling with the method below, I get the following error: 'Node' has no member named 'id' 'Node' has no member named 'next'

void append_node(Node *sent,int val){   
    Node *other_node = (struct Node *)malloc(1*sizeof(struct Node));
    other_node->id = val;
    Node n = *sent;
    while (n.next != NULL){
        n = n.next;
    }
    n.next = other_node;
}

Why is this error occurring?

EDIT:

I also have the following error

error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token

on the first line of the Node definition

A struct can not hold an instance of the same type as itself. — juanchopanza
– juanchopanza, Commented Oct 7, 2014 at 19:20
You probably meant: struct Node *next = NULL; (i.e. missing *). — isedev
– isedev, Commented Oct 7, 2014 at 19:20
dont think c can have default values in structs. atleast not c99 — sp2danny
– sp2danny, Commented Oct 7, 2014 at 19:26
Your code is mixing typedef references with (the prefered method) struct references. Use one of the other, but not both — user3629249
– user3629249, Commented Oct 8, 2014 at 0:04

radar · Accepted Answer · 2014-10-07 19:42:31Z

2

You can't have Node defined again inside the same structure. This will be infinite recursion.

you can have a Pointer to the same type.

typedef struct Node{
    struct Node *next;

edited Oct 7, 2014 at 19:42

answered Oct 7, 2014 at 19:21

radar

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4 Comments

sp2danny Over a year ago

does the implementation see the Node definition? is some other header also defining Node?

teaLeef Over a year ago

I am not sure what you mean (new to c). I defined the struct just before the main function

radar Over a year ago

@teaLeef, can you copy the code over to ideone to see it fully

teaLeef Over a year ago

Actually, it turns out the problem was that c99 can't have default values in structs. Thanks for your help

sp2danny · Accepted Answer · 2014-10-07 19:32:55Z

1

there are numerous errors in your code.
here is a correct version

typedef struct NodeTag
{
    struct NodeTag* next;
    int id;
} Node;

void append_node(Node* sent,int val)
{   
    Node* other_node = (Node*)malloc(sizeof(Node));
    other_node->id = val;
    other_node->next = 0;
    Node* n = sent;
    while (n->next != 0)
    {
        n = n->next;
    }
    n->next = other_node;
}

answered Oct 7, 2014 at 19:32

sp2danny

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1 Comment

teaLeef Over a year ago

I tried with this method, but when I call 'Node lr;' 'lr.number = 0;' 'add_node(&lr,2);'I get a seg fault. Any idea what is wrong?

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