Editing Pointer (computer programming) (section)

====C linked list====
Below is an example definition of a [[linked list]] in C.

<syntaxhighlight lang="C">
/* the empty linked list is represented by NULL
 * or some other sentinel value */
#define EMPTY_LIST  NULL

struct link {
    void        *data;  /* data of this link */
    struct link *next;  /* next link; EMPTY_LIST if there is none */
};
</syntaxhighlight>

This pointer-recursive definition is essentially the same as the reference-recursive definition from the language [[Haskell]]:

<syntaxhighlight lang="haskell">
 data Link a = Nil
             | Cons a (Link a)
</syntaxhighlight>
<code>Nil</code> is the empty list, and <code>Cons a (Link a)</code> is a [[cons]] cell of type <code>a</code> with another link also of type <code>a</code>.

The definition with references, however, is type-checked and does not use potentially confusing signal values. For this reason, data structures in C are usually dealt with via [[wrapper function]]s, which are carefully checked for correctness.