Your REXX procedures may need to include arithmetic operations of addition, subtraction, multiplication, and division. For example, you may want to assign a numeric value to two variables and then add the variables.
Arithmetic operations are performed the usual way. You can use whole numbers and decimal fractions. A whole number is an integer, or any number that is a natural number, either positive, negative, or zero, that does not contain a decimal part (for example, 1, 25, or 50). A decimal fraction contains a decimal point (for example, 1.45 or 0.6).
Before you see how these four operations are handled in a procedure, here is an explanation of what the operations look like and the symbols used. These are just a few of the arithmetic operations used in REXX.
┴╓: The examples contain a blank space between numbers and operators so that you can see the equations better, but the blank is optional.
Operators - The symbols used for arithmetic (+ , -, *, /) are called operators because they operate on the adjacent terms. In the following example, the operators act on the numbers (terms) 4 and 2:
SAY 4 + 2 /* says "6" */ SAY 4 * 2 /* says "8" */ SAY 4 / 2 /* says "2" */
Addition - The operator for addition is the plus sign (+). An instruction to add two numbers is:
SAY 4 + 2
The answer you see on your screen is 6.
Subtraction - The operator for subtraction is the minus sign (-). An instruction to subtract two numbers is:
SAY 8 - 3
The answer on your screen is 5.
Multiplication - The operator for multiplication is the asterisk (*). An instruction to multiply two numbers is:
SAY 2 * 2
The answer on your screen is 4.
Division - For division, there are several operators you can use, depending on whether or not you want the answer expressed as a whole number. For example, for a simple division, the symbol is one slash (/). An instruction to divide is:
SAY 7 / 2
The answer on your screen is 3.5.
To divide and return just a remainder, the operator is two slashes (//). To divide, and return only the whole number portion of an answer and no remainder, the operator is the percent sign (%).
For examples showing you how to perform four arithmetic operations on variables, select the Examples pushbutton.
Evaluating Expressions - Expressions are normally evaluated from left to right. An equation helps to illustrate this point. Until now, you have seen equations with only one operator and two terms, such as 4 + 2. Suppose you had this equation:
9 - 5 + 4 =
The 9 - 5 would be computed first. The answer, 4, would be added to 4 for a final value: 8.
Some operations are given priority over others. In general, the rules of algebra apply to equations. In this equation, the division is handled before the addition:
10 + 8 / 2 =
The value is 14.
If you use parentheses in an equation, the interpreter evaluates what is in the parentheses first. For example:
(10 + 8) / 2 =
The value is 9.