Expressions are made from operands (such as 47 and
x) and operators (such as + and
&&). Simple expressions such as x + 47
usually work just as anyone with some simple maths would expect. More
advanced expressions, such as x <= 47 && f(x, 47),
work as any C or C++ programmer would expect. Other expressions, such
as those involving mappings or set operations, are specific to Pike.