iTS 1.0+)

SCREEN COBOL Source Program

Compaq NonStop™ Pathway/iTS SCREEN COBOL Reference Manual—426750-001

2-15

Evaluation of Expressions

Parentheses can be used to specify the order in which the operations of an arithmetic

expression are performed. Expressions within parentheses are evaluated first.

Evaluation of expressions within nested parentheses proceeds from the innermost set to

the outermost set. When parentheses are not used, or expressions in parentheses are at

the same level, the order of execution is as follows:

1. Unary plus and minus

2. Multiplication and division

3. Addition and subtraction

Parentheses are used to eliminate ambiguities in logic or to modify the normal sequence

of execution in expressions where it is necessary to have some deviation. When the

sequence of execution is not specified by parentheses, the order for consecutive

operations at the same level is from left to right. The following example illustrates the

normal evaluation order in the absence of parentheses:

a + b / c + d * f - g

is interpreted as:

(a + (b / c)) + (d * f) - g

with the sequence of operations proceeding from the innermost parentheses to the

outermost. Expressions ordinarily considered ambiguous, such as:

a / b * c, a / b / c

are permitted in SCREEN COBOL. They are interpreted as if they were written:

(a / b) * c, (a / b) / c

Data items and literals appearing in an arithmetic expression must represent either

numeric elementary data items or numeric literals.

Multiple Results

The ADD, COMPUTE, MULTIPLY, and SUBTRACT statements can have multiple

results. Such statements behave as though they had been written in the following way:

1. One statement performs all necessary arithmetic to arrive at a result, and stores that

result in a temporary storage location.

2. A sequence of statements transfers or combines the value of this temporary location

with each result. These statements are considered to be written in the same left-to-

right sequence in which the multiple results are listed.

For example, the result of the following statement:

ADD a, b, c TO c, d(c), e