Programming in C

450 Appendix A C Language Summary
a + n
*(a + n)
produces a pointer to element number n of a, has type “pointer
to t,” and is in all ways equivalent to the expression &a[n];
references element number n of a, has type t, and is in all ways
equivalent to the expression a[n].
The actual type of the integer produced by subtracting two pointers is specified by
ptrdiff_t, which is defined in the standard header file .
Pointers to Structures 2
Given that
x is an lvalue expression of type struct s;
ps
is a modifiable lvalue expression of type “pointer to struct s”;
m is the name of a member of the structure s and is of type t;
v
is an expression;
then the expression
&x
produces a pointer to x and is of type “pointer to struct s”;
ps = &x
ps->m
(*ps).m
ps->m = v
sets ps pointing to x and is of type “pointer to struct s”;
references member m of the structure pointed to by ps and is of
type t;
also references this member and is in all ways equivalent to the expression
ps->m;
stores the value of v into the member m of the structure pointed to by
ps and is of type t.
5.16 Compound Literals
A compound literal is a type name enclosed in parentheses followed by an initialization
list. It creates an unnamed value of the specified type, which has scope limited to the
block in which it is created, or global scope if defined outside of any block. In the latter
case, the initializers must all be constant expressions.
As an example,
(struct point) {.x = 0, .y = 0}
is an expression that produces a structure of type struct point with the specified initial
values.This can be assigned to another struct point structure, as in
origin = (struct point) {.x = 0, .y = 0};
or passed to a function expecting an argument of struct point, as in
moveToPoint ((struct point) {.x = 0, .y = 0});
2. Also applies to unions.