HP C A.06.05 Reference Manual

Expressions and Operators
Relational Operators (>, >=, <, ==, !=)
Chapter 5126
Relational Operators (>, >=, <, ==, !=)
Syntax
exp1 > exp2 Greater than.
exp1 >= exp2 Greater than or equal to.
exp1 < exp2 Less than.
exp1 <= exp2 Less than or equal to.
exp1 == exp2 Equal to.
exp1 != exp2 Not equal to.
Arguments
exp1 Any expression.
exp2 Any expression.
Description
A relational expression consists of two expressions separated by one of six relational
operators. The relational expression evaluates either to 1 (true) or 0 (false).
The equality operator (==) performs the same function as Pascal's = or Fortran's .EQ.; it just
looks different. Although the equality operator looks similar to the assignment operator (=),
the two operators serve completely different purposes. Use the assignment operator when you
want to assign a value to a variable, but use the equality operator when you want to test the
value of an expression.
Confusing = with ==
One of the most common mistakes made by beginners and experts alike is to use the
assignment operator (=) instead of the equality operator (==). For instance:
while (j = 5)
do_something();
What is intended, clearly, is that the do_something() function should only be invoked if j
equals five. It should be written