"C" question. what does the arrow mark(-->) mean in "C"?

Question

i have an exam tomorrow. tell me please

here is an instance where it is used

int isempty(stack s)

{

if(s->next==null) // i don't know what operation the arrow mark does

return(1);

}

Answer 1

if next is defined as a pointer, then you use the arrow operator. if next is defined as a normal variable, then you use the dot operator. like this:

struct s {

int variable;

int *pointer;

};

.....

s->pointer // pointer

s.variable // a normal variable

Answer 2

-> is the structure pointer operator.

Example:

struct listNode {

  int val;

  struct listNode *next;

};

If you declare one of these:

struct listNode head;

you can access its members with the structure member operator . :

listNode.val = -1;

listNode.next = NULL;

If you have declare a pointer to one of these:

struct listNode *p = &head;

and want to access its members using p, you use the structure pointer operator -> :

p->val = 0;

For s->next == null in your example, s is most likely a pointer to a structure much like what I've shown above, an element of a linked list. Checking for null is the way to determine if the pointer s is referencing the last element of the list.

Answer 3

The arrow is ->, not -->.  On its left is the name of a pointer to a structure or union, and on the right it the name of a member of that structure or union.  In the example you give, the structure is being used to define a linked list, a very common and useful concept among C (and PL/I and assembly language) programmers:

typedef struct link

{

DATA data;

struct link *next;

} LINK, *PLINK;

A doubly linked list—one that can be traversed in either direction—would also declare struct link *previous.