C++ In a Nutshell

Expression Rules

C++ has the usual unary operators such as logical negation (!a), binary operators such as addition (a+b), and even a ternary operator (a?b:c). Unlike many other languages, an array subscript is also an operator (a[b]), and a function call is an n-ary operator (e.g., a(b, c, d)).

Every operator has a precedence . Operators with higher precedence are grouped so that they are logically evaluated before operators with lower precedence. (Note that precedence determines how the compiler parses the expression, not necessarily the actual order of computation. For example, in the expression a( ) + b( ) * c( ), the multiplication has higher precedence, but a( ) might be called first.)

Some operators group from left to right. For example, the expression x / y / z is equivalent to (x / y) / z. Other operators group right to left, as in x = y = z, which is equivalent to x = (y = z). The order of grouping is called the operator’s associativity.

When reading C++ expressions, you must be aware of the precedence and associativity of the operators involved. For example, *ptr++ is read as *(ptr++) because the postfix ++ operator has higher precedence than the unary * operator.

Table 3-1 summarizes the syntax, precedence, and associativity of each kind of expression. The subsections that follow describe the kinds of expressions in depth; each subsection covers a single precedence group.

Table 3-1. Expression syntax and associativity, grouped by precedence

Group	Associativity	Expression ...