HP C A.06.05 Reference Manual

Expressions and Operators
Array Subscripting ([ ])
Chapter 586
Array Subscripting ([ ])
A postfix expression followed by the [ ] operator is a subscripted reference to a single
element in an array.
Syntax
postfix-expression [ expression ]
Description
One of the operands of the subscript operator must be of type pointer to T (T is an object type),
the other of integral type. The resulting type is T.
The [ ] operator is defined so that E1[E2] is identical to (*((E1)+(E2))) in every respect.
This leads to the (counterintuitive) conclusion that the [ ] operator is commutative. The
expression E1[E2] is identical to E2[E1].
C's subscripts run from 0 to n-1 where n is the array size.
Multidimensional arrays are represented as arrays of arrays. For this reason, the notation is
to add subscript operators, not to put multiple expressions within a single set of brackets. For
example, int x[3][5] is actually a declaration for an array of three objects. Each object is, in
turn, an array of 5 int. Because of this, all of the following expressions are correct:
x
x[i]
x[i][j]
The first expression refers to the 3 by 5 array of int. The second refers to an array of 5 int, and
the last expression refers to a single int.
The expression x[y] is an lvalue.
There is no arbitrary limit on the number of dimensions that you can declare in an array.
Because of the design of multidimensional C arrays, the individual data objects must be
stored in row-major order.
As another example, the expression
a[i,j] = 0
looks as if array a were doubly subscripted, when actually the comma in the subscript
indicates that the value of i should be discarded and that j is the subscript into the a array.