WORDPERFECT MACRO TUTORIAL

11. Performing Arithmetic

11.1 The arithmetic operators

The basic arithmetic operators in PerfectScript are the following:

+ addition

- subtraction
* multiplication

/ division

% modulus
(gives the remainder when performing division)

Arithmetic can only be performed on numbers, not strings. (See the topic strings v. numbers earlier in the tutorial.) The items that are used by the operators to obtain the result are called operands, and the combination of operands and operator(s) is called an expression. What happens when the expression is performed is called the result. For example, in 2 + 4 = 6, 2 and 4 are the operands, + is the operator, 2+4 is the expression, and 6 is the result. Don't worry about remembering these terms; they are given to help with the explanations of other topics in the tutorial.

11.2 Assigning arithmetic results

You can assign the result of the arithmetic expression) to another variable, or to the same variable used in the expression. Remember that the expression on the right is assigned to the variable on the left. Examples:

vNum := ?Page + 5 Adds 5 to the value contained in the system variable ?Page, and assigns the result to vNum

x := y - 5 Subtracts 5 from the value of y, and assigns the result to x

vTotal := vEach * 10 Multiplies the value of vEach by 10 and assigns the result to vTotal

vHalf := vWhole / 2 Divides the values of vWhole by 2 and assigns the result to vHalf
vOdd := vAmt % 2 Divides the value of vAmount by 2, and assigns the remainder to vOdd

11.3 Order of precedence

Several arithmetic operations can be combined in one expression. But the order in which the operations are performed is governed by the rules of order of precendence, not just the position of the operation in the expression. The result of the expression 5*3+10 is the same as the result of 10+5*3, namely 25. That is because multiplication is always done before addition.

The important rule for order of precedence of operations in simple arithmetic is: multiplication and division are performed before addition and subtraction. Operations with the same order of precedence, i.e., multiplication and division, and addition and subtraction, are performed in order, left to right.

By putting expressions within parentheses, you can change the the order in which expressions are evaluated, because operations in parentheses are always performed first. For example, (10+5)*3 gives a result of 45, and 5*(3+10) gives a result of 65. If you are unsure about the order of precedence of operations, it is safest to put all operations within parentheses: (10+1)*(8-3). The operations within the parentheses are performed separately first, and then the results of those operations are used for the operation outside the parentheses, to give the final result. If this is part of an assignment to a variable, the final result is then assigned to the variable on the left side of the assignment.