HP 3000 Manuals HP 3000 Manuals
Chapter 5 Expressions
This chapter describes forming expressions in C, discusses operator
precedence, and provides details about operators used in expressions.
An expression in C is a collection of operators and operands that
indicates how a computation should be performed. Expressions are
represented in infix notation. Each operator has a precedence with
respect to other operators. Expressions are building blocks in C. You
use the C character set to form tokens. Tokens, combined together, form
expressions. Expressions can be used in statements.
The C language does not define the evaluation order of subexpressions
within a larger expression except in the special cases of the &&, ||, ?:,
and , operators. When programming in other computer languages, this may
not be a concern. C's rich operator set, however, introduces operations
that produce "side effects." The ++ operator is a prime example. The ++
operator increments a value by 1 and provides the value for further
calculations. For this reason, expressions such as
b = ++a*2 + ++a*4;
are dangerous. The language does not specify whether the variable a is
first incremented and multiplied by 4 or is first incremented and
multiplied by 2. The value of this expression is undefined.