979
One of the expressions shall have type “pointer to object
type”, the other expression shall have integer type,
and the result has type “type”.
980
A postfix expression followed by an expression in square brackets
[] is a subscripted designation of an element of
an array object.
981
The definition of the subscript operator [] is
that E1[E2] is identical to
(*((E1)+(E2))).
982
Because of the conversion rules that apply to the binary
+ operator, if E1 is an array
object (equivalently, a pointer to the initial element of an array
object) and E2 is an integer,
E1[E2] designates the E2-th element
of E1 (counting from zero).
983
Successive subscript operators designate an element of a
multidimensional array object.
984
If E is an n-dimensional array
(n≥2) with dimensions i × j × ...
× k then E (used as other than an
lvalue) is converted to a pointer to an (n−1)-dimensional
array with dimensions j × ... × k
985
If the unary * operator is applied to this pointer
explicitly, or implicitly as a result of subscripting, the result is
the pointed-to (n - 1)-dimensional array, which itself is
converted into a pointer if used as other than an lvalue.
986
It follows from this that arrays are stored in row-major order (last
subscript varies fastest).
987
EXAMPLE
Consider the array object defined by the declaration
int x[3][5];
Here x is a 3 × 5 array of
ints; more precisely, x is an
array of three element objects, each of which is an array of five
ints. In the expression x[i],
which is equivalent to (*((x)+(i))),
x is first converted to a pointer to the initial
array of five ints. Then i is
adjusted according to the type of x, which
conceptually entails multiplying i by the size of
the object to which the pointer points, namely an array of five
int objects. The results are added and
indirection is applied to yield an array of five
ints. When used in the expression
x[i][j], that array is in turn converted to a
pointer to the first of the ints, so
x[i][j] yields an int.