HP C/iX Reference Manual (31506-90011)

64 Chapter5

Expressions

Structure and Union Members

A member of a structure or a union can be referenced using either of two operators: the

period or the right arrow.

Syntax

postfix-expression . identifier

postfix-expression -> identifier

Description

Use the period to reference members of structures and unions directly. Use the arrow

operator to reference members of structures and unions pointed to by pointers. The arrow

operator combines the functions of indirection through a pointer and member selection. If

P is a pointer to a structure with a member M, the expression P->M is identical to (*P).M.

The postﬁx-expression in the ﬁrst alternative must be a structure or a union. The

expression is followed by a period (.) and an identiﬁer. The identiﬁer must name a member

deﬁned as part of the structure or union referenced in the postﬁx-expression. The value of

the expression is the value of the named member. It is an lvalue if the postﬁx-expression is

an lvalue.

If the postﬁx-expression is a pointer to a structure or a pointer to a union, follow it with an

arrow (composed of the - character followed by the >) and an identiﬁer. The identiﬁer must

name a member of the structure or union which the pointer references. The value of the

primary expression is the value of the named member. The resulting expression is an

lvalue.

The . operator and the -> operator are closely related. If S is a structure, M is a member of

structure S, and is a valid pointer expression, S.M is the same as (S)->M.