7.11.3 CASE Examples

Using the CASE command with OR operations

Using the CASE command with operations other than "=" (equal to)

Using the CASE command with compound expressions

Basic CASE Processing

This example illustrates the most basic type of CASE command processing.

Imagine that a user inputs a value into field #DEPTMENT and that a CASE command to be used to implement this logic:

When user inputs this value into field #DEPTMENT	Field #SECTION should be changed to this value . . .	And this message should be issued . . . .
ADM	A	ADM was entered
AUD	B	AUD was entered
FLT	C	FLT was entered
TRVL	D	TRVL was entered
Any other value	E	Other value was entered

Structurally, a CASE command to implement this logic would look like this:

   CASE       OF_FIELD(#DEPTMENT)
   WHEN       VALUE_IS('= ADM')
              << Logic >>
   WHEN       VALUE_IS('= AUD')
              << Logic >>
   WHEN       VALUE_IS('= FLT')
              << Logic >>
   WHEN       VALUE_IS('= TRVL')
             << Logic >>
   OTHERWISE 
              << Logic >>
   ENDCASE

A sample program to fully implement this logic might be coded like this:

   BEGIN_LOOP
   REQUEST    FIELDS(#DEPTMENT (#SECTION *OUTPUT))
   CASE       OF_FIELD(#DEPTMENT)
   WHEN       VALUE_IS('= ADM')
   CHANGE     FIELD(#SECTION) TO(A)
   MESSAGE    MSGTXT('ADM was entered')
   WHEN       VALUE_IS('= AUD')
   CHANGE     FIELD(#SECTION) TO(B)
   MESSAGE    MSGTXT('AUD was entered')
   WHEN       VALUE_IS('= FLT')
   CHANGE     FIELD(#SECTION) TO(C)
   MESSAGE    MSGTXT('FLT was entered')
   WHEN       VALUE_IS('= TRVL')
   CHANGE     FIELD(#SECTION) TO(D)
   MESSAGE    MSGTXT('TRVL was entered')
   OTHERWISE 
   CHANGE     FIELD(#SECTION) TO(E)
   MESSAGE    MSGTXT('Other value was entered')
   ENDCASE   
  END_LOOP

Why use the CASE command?

Imagine you have to implement this logic:

When field #DEPTMENT is this value ...	Field #SECTION should be changed to this value ...	And this message should be issued ....
ADM or FLT or TRVL	A	Either ADM , FLT or TRVL was entered
AUD or INF or MKT	B	Either AUD, INF or MKT was entered
Any other value	C	Other value was entered

If you code nested IF-ELSE-END blocks you will end up with logic like this:

   IF         COND('(#DEPTMENT = ADM) or (#DEPTMENT = FLT) or (#DEPTMENT = TRVL)')
   CHANGE     FIELD(#SECTION) TO(A)
   MESSAGE    MSGTXT('Either ADM , FLT or TRVL was entered')
   ELSE      
   IF         COND('(#DEPTMENT = AUD) or (#DEPTMENT = INF) or (#DEPTMENT = MKT)')
   CHANGE     FIELD(#SECTION) TO(B)
   MESSAGE    MSGTXT('Either AUD, INF or MKT was entered')
   ELSE      
   CHANGE     FIELD(#SECTION) TO(C)
   MESSAGE    MSGTXT('Other value was entered')
   ENDIF     
   ENDIF

However, by using a CASE command you can code this instead:

   CASE       OF_FIELD(#DEPTMENT)
   WHEN       VALUE_IS('= ADM' '= FLT' '= TRVL')
   CHANGE     FIELD(#SECTION) TO(A)
   MESSAGE    MSGTXT('Either ADM, FLT or TRVL was entered')
   WHEN       VALUE_IS('= AUD' '= INF' '= MKT')
   CHANGE     FIELD(#SECTION) TO(B)
   MESSAGE    MSGTXT('Either AUD, INF or MKT was entered')
   OTHERWISE 
   CHANGE     FIELD(#SECTION) TO(C)
   MESSAGE    MSGTXT('Other value was entered')
   ENDCASE

Which is shorter, easier to read, and easier to maintain.

It also executes faster in most situations.

Using the CASE command with OR operations

Imagine that when field #TEST contains A or B or C you have to perform some operation.

If it contains X or Y or Z you have to perform some other operation.

If it contains any other value then you have to perform yet another operation.

You could use a CASE command structured like this to implement the required logic:

   CASE       OF_FIELD(#TEST)
        
   WHEN       VALUE_IS('= A' '= B' '= C')          

             << Logic Block 1 >>
          
   WHEN       VALUE_IS('= X' '= Y' '= Z')

             << Logic Block 2>>          

   OTHERWISE 
        
             << Logic Block 3>>         
   
   ENDCASE

Using the CASE command with operations other than "=" (equal to)

Imagine that when field #COPIES needs to be validated according to these rules:

Value of #COPIES	Message to Issue
= 0	Value of zero is invalid
< 0	Value is negative !
1 to 50	Value is sensible
> 50	Value is probably incorrect

Hence a CASE command can be used like this:

      DEFINE     FIELD(#COPIES) TYPE(*DEC) LENGTH(3) DECIMALS(0) EDIT_CODE(N) DEFAULT(+1)
      BEGIN_LOOP
      REQUEST    FIELDS(#COPIES)
      CASE       OF_FIELD(#COPIES)
      WHEN       VALUE_IS('= 0')
      MESSAGE    MSGTXT('Value of zero is invalid')
      WHEN       VALUE_IS('< 0')
      MESSAGE    MSGTXT('Value is negative')
      WHEN       VALUE_IS('<= 50')
      MESSAGE    MSGTXT('Value is sensible')
      OTHERWISE 
      MESSAGE    MSGTXT('Value is probably incorrect')
      ENDCASE   

   END_LOOP

Using the CASE command with compound expressions

In a situation whereby a field #DISCOUNT needs to be validated by using a mathematical calculation such as this:

When user inputs this value into fields #DISCOUNT, #QUANTITY	This equation is used to validate the discount value	A message will be displayed
1000, 20	#QUANTITY * 0.1	Discount value is larger than QUANTITY times 0.1
10, 200	#QUANTITY * 0.1	Discount value is less than QUANTITY times 0.1
10, 100	#QUANTITY * 0.1	A correct discount value was entered

This can be coded by using the CASE command:

   DEFINE     FIELD(#DISCOUNT) TYPE(*DEC) LENGTH(11) DECIMALS(2) EDIT_CODE(1)
   DEFINE     FIELD(#QUANTITY) TYPE(*DEC) LENGTH(3) DECIMALS(0)
   BEGIN_LOOP
   REQUEST    FIELDS(#DISCOUNT #QUANTITY)
   CASE       OF_FIELD(#DISCOUNT)
   WHEN       VALUE_IS('> (#QUANTITY * 0.1)')
   MESSAGE    MSGTXT('Discount value is larger than quantity times 0.1')
   WHEN       VALUE_IS('< (#QUANTITY * 0.1)')
   MESSAGE    MSGTXT('Discount value is less than quantity times 0.1')
   OTHERWISE 
   MESSAGE    MSGTXT('A correct discount value was entered')
   ENDCASE   
   END_LOOP