MACROMEDIA ColdFusion MX, Develop Manual

Page: 84 / 860

84 Chapter 4: Using Expressions and Pound Signs
Expressions
ColdFusion expressions consist of operands and operators . Operands are comprised of constants
and variables. Operators, such as the multiplication symbol, are the verbs that act on the
operands; functions are a form of operator.
The simplest expression consists of a single operand with no operators. Complex expressions have
multiple operators and operands. The following are all ColdFusion expressions:
12
MyVariable
(1 + 1)/2
"father" & "Mother"
Form.divisor/Form.dividend
Round(3.14159)
Operators act on the operands. Some operators, such as functions with a single argument, take a
single operand. Many operators, including most arithmetic and logical operators, take two
operands. The following is the general form of a two-operand expression:
Expression Operator Expression
Note that the operator is surrounded by expressions. Each expression can be a simple operand
(variable or constant) or a
subexpression consisting of more operators and expressions. Complex
expressions are built up using subexpressions. For example, in the expression (1 + 1)/2, 1 + 1 is a
subexpression consisting of an operator and two operands.
Operator types
ColdFusion has four types of operators:
•
Arithmetic
•
Boolean
•
Decision (or comparison)
•
String
Functions also can be viewed as operators because they act on operands.
Arithmetic operators
The following table describes the arithmetic operators:
Operator Description
+ - * / Basic arithmetic: Addition, subtraction, multiplication, and division. In division, the right
operand cannot be zero.
+ - Unary arithmetic: Set the sign of a number.
MOD Modulus: Return the remainder after a number is divided by a divisor. The result has the
same sign as the divisor. The right should be an integer; using a non-numeric value
causes an error, and if you specify a real number, ColdFusion ignores the fractional part
(for example, 11 MOD 4 is 3).