CODEWITHSUNDEEP
ctypedef
Elias Bats
Elias Bats

Reputation: 55

Eliminate use of typedef in a linked list program

I am studying linked lists and (among other, simpler implementations) I encountered this example:

typedef struct ListNode_tag {
   int data;
   struct ListNode_tag * next;
} ListNode;
/* linked list */
typedef ListNode * slist;


void slistInsert (slist * lp, int t)
{
    ListNode * n = (ListNode *) malloc(sizeof(ListNode));
    n->data = t;
    n->next = *lp;
    *lp = n;
}

void slistPrint (slist l)
{
    while (l != NULL) {
        printf("%d\n", l->data);
        l = l->next;}
}

int main ()
{
    slist l = NULL;
    slistInsert(&l, 13);
    slistInsert(&l, 42);
    slistPrint(l); //print 42 13
    return 0;
}

...which seems to work ok, but if I had to eliminate the use of typedef I cannot understand which changes I should make. I have tried some solutions but they didn't work.

Upvotes: 2

Views: 414

Answers (3)

Milind Dumbare
Milind Dumbare

Reputation: 3244

typedefs are like simple naming for a complex declaration.

It is easy to write slist instead of struct ListNode_tag *

Replace all occurrences of ListNode with struct ListNode_tag. And slist with struct ListNode_tag *

And your structure will look like this

struct ListNode_tag {
   int data;
   struct ListNode_tag * next;
};

slistInsert() declaration looks like this

void slistInsert (struct ListNode_tag **lp, int t)

slistPrint() declaration looks like this

void slistPrint (struct ListNode_tag * l)

Upvotes: 1

Vlad from Moscow
Vlad from Moscow

Reputation: 311126

Here is the program without typedef(s).

#include <stdio.h>
#include <stdlib.h>

struct ListNode {
   int data;
   struct ListNode * next;
};
/* linked list */


void slistInsert (struct ListNode **lp, int t)
{
    struct ListNode * n = (struct ListNode *) malloc(sizeof(struct ListNode));
    n->data = t;
    n->next = *lp;
    *lp = n;
}

void slistPrint (struct ListNode *l)
{
    while (l != NULL) {
        printf("%d\n", l->data);
        l = l->next;}
}

int main ()
{
    struct ListNode *l = NULL;
    slistInsert(&l, 13);
    slistInsert(&l, 42);
    slistPrint(l); //print 42 13
    return 0;
}

Take into account that you need also to write a function that will free all allocated memory for the list.

Upvotes: 1

shf301
shf301

Reputation: 31404

A typedef is just an alias, a different name for something that already exists. So typedef ListNode * slist; creates an alias slist for ListNode*. Since sList is the same as ListNode* just replace slist with ListNode*.

The other typedef, typedef struct ListNode_tag {...} ListNode; creates an alias ListNode for struct ListNode_tag. So replace ListNode with struct ListNode_tag. In C the keyword struct has to be included with the struct's name.

Upvotes: 1

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