EVALUATE Statement [ HP COBOL II Reference Manual ]
HP COBOL II Reference Manual
EVALUATE Statement
The EVALUATE statement adds a multi-condition case construct to COBOL.
This statement causes a set of subjects to be evaluated and compared with
a set of objects. The results of these evaluations determine the
subsequent sequence of code execution.
This statement has the following format:
Click here to view figure.
Subjects and Objects
The operands or the words TRUE and FALSE that appear before the first
WHEN phrase of the EVALUATE statement are referred to individually as
subjects. Collectively, they are referred to as the set of subjects.
The operands or the words TRUE, FALSE, and ANY that appear in a WHEN
phrase of an EVALUATE statement are individually called objects.
Collectively, they are called the set of objects.
The words THROUGH and THRU are equivalent.
Two operands connected by a THROUGH phrase must be of the same class.
The two connected operands constitute a single object.
The number of objects within each set of objects must be equal to the
number of subjects.
Correspondence Between Subjects and Objects. A subject-object pair
consists of a subject and object having the same ordinal position within
each set. Each pair must conform to the following rules:
* Identifiers, literals, and arithmetic expressions must be valid
operands for a comparison between the subject and object.
* Conditions, or the words TRUE or FALSE appearing as an object must
correspond to a conditional expression or the words TRUE or FALSE.
* The word ANY may correspond to a selection subject of any type.
Evaluation of Subjects and Objects. Execution of the EVALUATE statement
operates as if each subject and object were evaluated and assigned a
numeric or nonnumeric value, a range of numeric or nonnumeric values, or
a truth value. These values are determined as follows:
* Any subject or object specified by an identifier, without either the
NOT or the THROUGH phrases, is assigned the value and class of the
data item referenced by the identifier.
* Any subject or object specified by a literal, without either the NOT
or the THROUGH phrases, is assigned the value and class of the
specified literal. When an object is assigned the figurative
constant ZERO, it is assigned the class of the corresponding subject.
* Any subject or object in which an expression is specified as an
arithmetic expression without either the NOT or the THROUGH phrases,
is assigned a numeric value according to the rules for evaluating an
arithmetic expression. (Refer to Chapter 8, under "Arithmetic
Expressions".)
* A subject or object specified by a conditional expression is assigned
a truth value according to the rules for evaluating conditional
expressions. (Refer to Chapter 8, "Conditional Expressions".)
* A subject or object specified by the words TRUE or FALSE is assigned
the appropriate truth value.
* No further evaluation is done for an object specified by the word
ANY.
* If the THROUGH phrase is specified for an object, without the NOT
phrase, the range of values includes all values of the subject that
are greater than or equal to the first operand and less than or equal
to the second operand.
* If the NOT phrase is specified for an object, the values assigned to
that item are all values that are not equal to the value, or included
in the range of values, that would have been assigned to the item
without the NOT phrase.
Refer to Chapter 8, "Relation Conditions," for more information on NOT
phrases.
Comparison Operation of EVALUATE
The execution of the EVALUATE statement proceeds as if the values
assigned to the subjects and objects were compared, to determine if any
WHEN phrase satisfies the set of subjects. This comparison proceeds as
follows:
1. A subject-object pair comparison is satisfied if the following
conditions are true:
a. If the items being compared are assigned numeric or nonnumeric
values or a range of numeric or nonnumeric values, the
comparison is satisfied if the value, or one of the range of
values, assigned to the object is equal to the value assigned
to the subject.
b. If the items being compared are assigned truth values, the
comparison is satisfied if the items are assigned the
identical truth values.
c. If the object being compared is specified by the word ANY, the
comparison is always satisfied, regardless of the value of the
subject.
2. If the above comparison is satisfied for every object within the
set of objects being compared, the first WHEN phrase for which
each subject-object pair comparison is satisfied is selected as
the one that satisfies the set of subjects.
3. If the above comparison is not satisfied for one or more objects
within the set of objects being compared, that set of objects does
not satisfy the set of subjects.
4. This procedure is repeated for subsequent sets of objects in the
order of their appearance in the source program. The comparison
operation continues until either a WHEN phrase that satisfies the
set of subjects is selected, or until all sets of objects are
exhausted.
Execution of EVALUATE
After the comparison operation is completed, execution of the EVALUATE
statement proceeds as follows:
1. If a WHEN phrase is selected, execution continues with the first
imperative statement following the selected WHEN phrase.
2. If no WHEN phrase is selected and a WHEN OTHER phrase is
specified, execution continues with the imperative statement
following the WHEN OTHER phrase.
3. The execution of the EVALUATE statement is terminated when
execution reaches the end of the imperative statement of the
selected WHEN phrase, or when no WHEN phrase is selected and no
WHEN OTHER phrase is specified.
Examples
EVALUATE HOURS-WORKED ALSO EXEMPT
WHEN 0 ALSO ANY PERFORM NO-PAY
WHEN NOT 0 ALSO "Y" PERFORM SALARIED
WHEN 1 THRU 40 ALSO "N" PERFORM HOURLY-PAY
WHEN NOT 1 THRU 40 ALSO "NO" PERFORM OVERTIME-PAY
WHEN OTHER
DISPLAY HOURS-WORKED
DISPLAY EXEMPT
MOVE 0 TO HOURS-WORKED
END-EVALUATE
EVALUATE GRADE > 3.0 ALSO COLLEGE-CODE
WHEN TRUE ALSO "01"
PERFORM DEANS-LIST-AGGIES
WHEN TRUE ALSO "02"
PERFORM DEANS-LIST-S-AND-H
WHEN TRUE ALSO "03"
PERFORM DEANS-LIST-ENG
WHEN TRUE ALSO ANY
PERFORM MISC-LIST.
Click here to view figure.
Subjects and Objects
The operands or the words TRUE and FALSE that appear before the first
WHEN phrase of the EVALUATE statement are referred to individually as
subjects. Collectively, they are referred to as the set of subjects.
The operands or the words TRUE, FALSE, and ANY that appear in a WHEN
phrase of an EVALUATE statement are individually called objects.
Collectively, they are called the set of objects.
The words THROUGH and THRU are equivalent.
Two operands connected by a THROUGH phrase must be of the same class.
The two connected operands constitute a single object.
The number of objects within each set of objects must be equal to the
number of subjects.
Correspondence Between Subjects and Objects. A subject-object pair
consists of a subject and object having the same ordinal position within
each set. Each pair must conform to the following rules:
* Identifiers, literals, and arithmetic expressions must be valid
operands for a comparison between the subject and object.
* Conditions, or the words TRUE or FALSE appearing as an object must
correspond to a conditional expression or the words TRUE or FALSE.
* The word ANY may correspond to a selection subject of any type.
Evaluation of Subjects and Objects. Execution of the EVALUATE statement
operates as if each subject and object were evaluated and assigned a
numeric or nonnumeric value, a range of numeric or nonnumeric values, or
a truth value. These values are determined as follows:
* Any subject or object specified by an identifier, without either the
NOT or the THROUGH phrases, is assigned the value and class of the
data item referenced by the identifier.
* Any subject or object specified by a literal, without either the NOT
or the THROUGH phrases, is assigned the value and class of the
specified literal. When an object is assigned the figurative
constant ZERO, it is assigned the class of the corresponding subject.
* Any subject or object in which an expression is specified as an
arithmetic expression without either the NOT or the THROUGH phrases,
is assigned a numeric value according to the rules for evaluating an
arithmetic expression. (Refer to Chapter 8, under "Arithmetic
Expressions".)
* A subject or object specified by a conditional expression is assigned
a truth value according to the rules for evaluating conditional
expressions. (Refer to Chapter 8, "Conditional Expressions".)
* A subject or object specified by the words TRUE or FALSE is assigned
the appropriate truth value.
* No further evaluation is done for an object specified by the word
ANY.
* If the THROUGH phrase is specified for an object, without the NOT
phrase, the range of values includes all values of the subject that
are greater than or equal to the first operand and less than or equal
to the second operand.
* If the NOT phrase is specified for an object, the values assigned to
that item are all values that are not equal to the value, or included
in the range of values, that would have been assigned to the item
without the NOT phrase.
Refer to Chapter 8, "Relation Conditions," for more information on NOT
phrases.
Comparison Operation of EVALUATE
The execution of the EVALUATE statement proceeds as if the values
assigned to the subjects and objects were compared, to determine if any
WHEN phrase satisfies the set of subjects. This comparison proceeds as
follows:
1. A subject-object pair comparison is satisfied if the following
conditions are true:
a. If the items being compared are assigned numeric or nonnumeric
values or a range of numeric or nonnumeric values, the
comparison is satisfied if the value, or one of the range of
values, assigned to the object is equal to the value assigned
to the subject.
b. If the items being compared are assigned truth values, the
comparison is satisfied if the items are assigned the
identical truth values.
c. If the object being compared is specified by the word ANY, the
comparison is always satisfied, regardless of the value of the
subject.
2. If the above comparison is satisfied for every object within the
set of objects being compared, the first WHEN phrase for which
each subject-object pair comparison is satisfied is selected as
the one that satisfies the set of subjects.
3. If the above comparison is not satisfied for one or more objects
within the set of objects being compared, that set of objects does
not satisfy the set of subjects.
4. This procedure is repeated for subsequent sets of objects in the
order of their appearance in the source program. The comparison
operation continues until either a WHEN phrase that satisfies the
set of subjects is selected, or until all sets of objects are
exhausted.
Execution of EVALUATE
After the comparison operation is completed, execution of the EVALUATE
statement proceeds as follows:
1. If a WHEN phrase is selected, execution continues with the first
imperative statement following the selected WHEN phrase.
2. If no WHEN phrase is selected and a WHEN OTHER phrase is
specified, execution continues with the imperative statement
following the WHEN OTHER phrase.
3. The execution of the EVALUATE statement is terminated when
execution reaches the end of the imperative statement of the
selected WHEN phrase, or when no WHEN phrase is selected and no
WHEN OTHER phrase is specified.
Examples
EVALUATE HOURS-WORKED ALSO EXEMPT
WHEN 0 ALSO ANY PERFORM NO-PAY
WHEN NOT 0 ALSO "Y" PERFORM SALARIED
WHEN 1 THRU 40 ALSO "N" PERFORM HOURLY-PAY
WHEN NOT 1 THRU 40 ALSO "NO" PERFORM OVERTIME-PAY
WHEN OTHER
DISPLAY HOURS-WORKED
DISPLAY EXEMPT
MOVE 0 TO HOURS-WORKED
END-EVALUATE
EVALUATE GRADE > 3.0 ALSO COLLEGE-CODE
WHEN TRUE ALSO "01"
PERFORM DEANS-LIST-AGGIES
WHEN TRUE ALSO "02"
PERFORM DEANS-LIST-S-AND-H
WHEN TRUE ALSO "03"
PERFORM DEANS-LIST-ENG
WHEN TRUE ALSO ANY
PERFORM MISC-LIST.