CASE statement

Provides a multi-branch decision based on the value of a single expression.

Syntax


CASE `expression` : { WHEN `value` [ OR WHEN `value` ] ... THEN { `block` \| `statement` } } ... [ OTHERWISE { `block` \| `statement` } ] END [ CASE ]

expression

The expression that determines which branch of code to execute. The expression parameter can be any valid ABL expression. It can include comparisons, logical operations, and parentheses.

WHEN value [ OR WHEN value ] . . . THEN

Each value is an expression that evaluates to a possible value for expression. If value matches the current value of expression, then the associated block or statement executes.

OTHERWISE

Introduces a block or statement to execute when the value of expression does not match any value in any of the WHEN clauses.

block

A DO, FOR, or REPEAT block. If you do not use a block, then you can only use a single statement for the WHEN or OTHERWISE clause.

statement

A single ABL statement. If you want to use more than one statement, you must enclose them in a DO, FOR, or REPEAT block.

END [ CASE ]

Indicates the end of the CASE statement. You can include the CASE keyword here to improve readability; it has no effect on the code.

Example

The following fragment shows a simple example of a CASE statement:

r-case.p
DEFINE VARIABLE pay-stat AS INTEGER NO-UNDO INITIAL 1. UPDATE pay-stat VIEW-AS RADIO-SET RADIO-ITEM unpaid 1 LABEL "Unpaid" RADIO-ITEM part 2 LABEL "Partially paid" RADIO-ITEM paid 3 LABEL "Paid in full". CASE pay-stat: WHEN 1 THEN MESSAGE "This account is unpaid.". WHEN 2 THEN MESSAGE "This account is partially paid.". WHEN 3 THEN MESSAGE "This account is paid in full.". END CASE.

r-case.p

DEFINE VARIABLE pay-stat AS INTEGER NO-UNDO INITIAL 1. 
UPDATE pay-stat VIEW-AS RADIO-SET 
  RADIO-ITEM unpaid   1 LABEL "Unpaid" 
  RADIO-ITEM part     2 LABEL "Partially paid" 
  RADIO-ITEM paid     3 LABEL "Paid in full". 
CASE pay-stat: 
  WHEN 1 THEN 
    MESSAGE "This account is unpaid.". 
  WHEN 2 THEN   
    MESSAGE "This account is partially paid.". 
  WHEN 3 THEN   
    MESSAGE "This account is paid in full.". 
END CASE.

Notes

Each value must have the same data type as expression. If the data types do not match, the compiler reports an error.

You can specify any number of WHEN clauses within the CASE statement.

You can specify only one OTHERWISE clause for a CASE statement. If you use the OTHERWISE clause, it must be the last branch in the statement.

When a CASE statement is executed, the AVM evaluates expression and evaluates each value for each branch in order of occurrence until it finds the first value that satisfies the condition. At that point the AVM executes that branch and does not evaluate any other value for that branch or any other branches. If no matching value is found, then the OTHERWISE branch is executed, if given. If the OTHERWISE branch is not given and no matching value is found, then no branch of the CASE statement is executed and execution continues with the statement after the CASE statement.

After a branch of the CASE statement is executed, the AVM leaves the CASE statement and execution continues with the statement following the CASE statement.

If a LEAVE statement is executed within any branch of a CASE statement, the AVM leaves the closest block (other than a DO block) that encloses the CASE statement.