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HP COBOL
Reference Manual

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6.5.6 Success/Failure Condition

The success/failure condition tests the return status codes of COBOL and non-COBOL procedures for success or failure conditions.

status-code-id

must be a COMP integer represented by PIC 9(1 to 9) COMP or PIC S9(1 to 9) COMP.

You can use the SET statement to initialize or alter the status of status-code-id.

The SUCCESS class condition is true if you specify status-code-id IS SUCCESS and status-code-id is in a SUCCESS state. Otherwise, the SUCCESS class condition is false.

The FAILURE class condition is true if you specify status-code-id IS FAILURE and status-code-id is in a FAILURE state. Otherwise, the FAILURE class condition is false.

status-code-id is in the SUCCESS state when the low-order bit of status-code-id is 1. It is in the FAILURE state when its low-order bit is 0.

Examples

  1. On OpenVMS, calling a non-COBOL procedure: 


    WORKING-STORAGE SECTION.
01  RMS-EOF       PIC S9(9) COMP VALUE EXTERNAL RMS$_EOF.
01  RETURN-STATUS PIC S9(9) COMP.
PROCEDURE DIVISION.
A000-BEGIN.
    .
    .
    .
    CALL "LIB$GET_SCREEN"
              USING BY DESCRIPTOR INPUT-TEXT, PROMPT,
                    BY REFERENCE  OUT-LEN,
              GIVING RETURN-STATUS.
    IF RETURN-STATUS = RMS-EOF PERFORM CTRL-Z-TRAP-ROUTINE.
    IF RETURN-STATUS IS FAILURE PERFORM FAILURE-ROUTINE.
    .
    .
    .                                            <>

  2. Calling a COBOL procedure: 


    IDENTIFICATION DIVISION.
PROGRAM-ID. MAIN-PROGRAM.
DATA DIVISION.
WORKING-STORAGE SECTION.
01  RETURN-STATUS      PIC S9(9) COMP.
PROCEDURE DIVISION.
    .
    .
    .
    CALL "SUB" GIVING RETURN-STATUS.
    IF RETURN-STATUS IS FAILURE PERFORM FAILURE-ROUTINE.
    .
    .
    .
IDENTIFICATION DIVISION.
PROGRAM-ID. SUB.
    .
    .
    .
WORKING-STORAGE SECTION.
01  RETURN-STATUS      PIC S9(9) COMP.
PROCEDURE DIVISION GIVING RETURN-STATUS.
    .
    .
    .
    IF A = B
           SET RETURN-STATUS TO SUCCESS
       ELSE
           SET RETURN-STATUS TO FAILURE.
    .
    .
    .
    EXIT PROGRAM.
END PROGRAM SUB.
END PROGRAM MAIN-PROGRAM.

6.5.7 Complex Conditions

You form complex conditions by combining or negating other conditions. The conditions being combined or negated can be either simple or complex.

The logical operators AND and OR combine conditions. The logical operator NOT negates conditions. A space must precede and follow each logical operator in your program.

The truth value of a complex condition depends upon the following:

  • The truth value of each condition it contains
  • The effect of the logical operators

Table 6-4 shows the effect of each logical operator in complex conditions.

Table 6-4 How Logical Operators Affect Evaluation of Conditions
Logical
Operator 		Meaning and Effect
AND Logical conjunction. The truth value is true if both connected conditions are true. It is false if one or both connected conditions are false.
OR Logical inclusive OR. The truth value is true if one or both connected conditions are true. It is false if both conditions are false.
NOT Logical negation or reversal of truth value. The truth value is true if the original condition is false. It is false if the original condition is true.

Negated Simple Conditions

The logical operator NOT negates a simple condition. The truth value of a negated simple condition is the opposite of the simple condition's truth value. Thus, the truth value of a negated simple condition is true only if the simple condition's truth value is false. It is false only if the simple condition's truth value is true.

The format for a negated simple condition is as follows:

Combined and Negated Combined Conditions

A combined condition results from connecting conditions with one of the logical operators AND or OR.

The general format is as follows:

In the general format, condition can be one of the following:

  • A simple condition
  • A negated simple condition
  • A combined condition
  • A negated combined condition; that is, NOT followed by a combined condition enclosed in parentheses
  • Valid combinations of the preceding conditions (see Table 6-5)

You can use matched pairs of parentheses in a combined condition. You do not need to write parentheses if the condition combines two or more conditions with the same logical operator (either AND or OR). In this case, the parentheses have no effect on the condition's evaluation. However, you might have to use parentheses if you use a mixture of AND, OR, and NOT logical operators. In this case, the parentheses can affect the condition's evaluation.

When the relevant parentheses are missing from a complex condition, the evaluation order of the logical operators determines the conditions to which the specified logical operators apply and implies the equivalent parentheses. The evaluation order is NOT, AND, OR. Thus, specifying: 


  a OR NOT b AND c

implies and is equivalent to specifying: 


  a OR ((NOT b) AND c)

(See also Section 6.5.9.)

Table 6-5 shows the permissible combinations of conditions, logical operators, and parentheses.

Table 6-5 Combinations of Conditions, Logical Operators, and Parentheses
  In a Conditional Expression In a Left-to-Right Element Sequence
Element Can
Element
Be First? 		Can
Element
Be Last? 		Element, When Not First, Can Immediately Follow Element, When Not Last, Can Immediately Precede
simple-
condition 		Yes Yes OR, NOT, AND, ( OR, AND, )
OR or AND No No simple-condition, ) simple-condition, NOT, (
NOT Yes No OR, AND, ( simple-condition, (
( Yes No OR, NOT, AND, ( simple-condition, NOT, (
) No Yes simple-condition, ) OR, AND, )

For example, Table 6-5 shows whether or not the following element pairs can occur in your program:

Element
Pair 		Permitted?
OR NOT Yes
NOT OR No
NOT ( Yes
NOT NOT No

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