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This guideline is very simple, yet it will allow LANSA programs to be completed more quickly and accurately.

When working on the code of a specific RDML function, always attempt to use a "top down" approach to coding. For instance, you may be given a program "specification" which looks like this:

  • Repeat until program terminated at user request
    • Get the user to input an order number
    • Get details of the order, and handle record not found
    • Get details of all the order lines
    • Display the order details and the line details

You must now "translate" this specification into the LANSA rapid development language.

With a structured (or organized) approach to coding, the program will follow similar steps to the example below.

Note how the arrow --> is used to indicate the new lines inserted in each step:

Step 1

...

     --> ********** Do until terminated by EXIT or MENU key

...

     --> BEGIN_LOOP

...

     --> END_LOOP

...

Step 2
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
     --> ********** Request order number input until order is found
...
     --> ********** Build a list of all order lines
...
     --> ********** Display the order and its lines to the user
...
         END_LOOP 
...
Step 3
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
     --> DOUNTIL    COND('#IO$STS = OK')
...
     --> ENDUNTIL
...
         ********** Build a list of all order lines
...
         ********** Display the order and its lines to the user
...
         END_LOOP
...
Step 4
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
     --> CLR_LIST   NAMED(#LINES)
...
     --> SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
     --> ENDSELECT
...
         ********** Display the order and its lines to the user
...
         END_LOOP
...
Step 5
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
         CLR_LIST   NAMED(#LINES)
...
         SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
         ENDSELECT
...
         ********** Display the order and its lines to the user
...
     --> DISPLAY    FIELDS(#HEADER) BROWSELIST(#LINES)
...
         END_LOOP
...
Step 6
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
     --> ********** Request user inputs an order number
...
     --> ********** Attempt to locate the order
...
     --> ********** Issue message if order was not found
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
         CLR_LIST   NAMED(#LINES)
...
         SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
         ENDSELECT
...
         ********** Display the order and its lines to the user
...
         DISPLAY    FIELDS(#HEADER) BROWSELIST(#LINES)
...
         END_LOOP
...
Step 7
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
         ********** Request user inputs an order number
...
         REQUEST    FIELDS(#ORDNUM)
...
         ********** Attempt to locate the order
...
     --> FETCH      FIELDS(#HEAD) FROM_FILE(ORDMST) WITH_KEY(#ORDNUM)
...
         ********** Issue message if order was not found
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
         CLR_LIST   NAMED(#LINES)
...
         SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
         ENDSELECT
...
         ********** Display the order and its lines to the user
...
         DISPLAY    FIELDS(#HEADER) BROWSELIST(#LINES)
...
         END_LOOP 
...
Step 8
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
         ********** Request user inputs an order number
...
         REQUEST    FIELDS(#ORDNUM)
...
         ********** Attempt to locate the order
...
         FETCH      FIELDS(#HEAD) FROM_FILE(ORDMST) WITH_KEY(#ORDNUM)
...
         ********** Issue message if order was not found
...
     --> IF_STATUS  WAS_NOT(*OKAY)
...
     --> ENDIF
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
         CLR_LIST   NAMED(#LINES)
...
         SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
         ENDSELECT
...
         ********** Display the order and its lines to the user
...
         DISPLAY    FIELDS(#HEADER) BROWSELIST(#LINES)
...
         END_LOOP 
Step 9
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
         ********** Request user inputs an order number
...
         REQUEST    FIELDS(#ORDNUM)
...
         ********** Attempt to locate the order
...
         FETCH      FIELDS(#HEAD) FROM_FILE(ORDMST) WITH_KEY(#ORDNUM)
...
         ********** Issue message if order was not found
...
         IF_STATUS  WAS_NOT(*OKAY)
...
     --> MESSAGE    MSGTXT('No details of this order found')
...
         ENDIF
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
         CLR_LIST   NAMED(#LINES)
...
         SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
         ENDSELECT
...
         ********** Display the order and its lines to the user
...
         DISPLAY    FIELDS(#HEADER) BROWSELIST(#LINES)
...
         END_LOOP
...
Step 10
...
         ********** Do until terminated by EXIT or MENU key
...
         BEGIN_LOOP
...
         ********** Request order number until order is found
...
         DOUNTIL    COND('#IO$STS = OK')
...
         ********** Request user inputs an order number
...
         REQUEST    FIELDS(#ORDNUM)
...
         ********** Attempt to locate the order
...
         FETCH      FIELDS(#HEAD) FROM_FILE(ORDMST) WITH_KEY(#ORDNUM)
...
         ********** Issue message if order was not found
...
         IF_STATUS  WAS_NOT(*OKAY)
...
         MESSAGE    MSGTXT('No details of this order found')
...
         ENDIF
...
         ENDUNTIL
...
         ********** Build a list of all order lines
...
         CLR_LIST   NAMED(#LINES)
...
         SELECT     FIELDS(#LINES) FROM_FILE(ORDLIN) WITH_KEY(#ORDNUM)
...
     --> ADD_ENTRY  TO_LIST(#LINES)
...
         ENDSELECT
...
         ********** Display the order and its lines to the user
...
         DISPLAY    FIELDS(#HEADER) BROWSELIST(#LINES)
...
         END_LOOP
...
You should find that well structured and documented programs are very easy to produce by using this type of approach, which basically consists of always:
  • entering the structured programming constructs completely before coming back to fill in the details. For example:   BEGIN_LOOP/END_LOOP, DOUNTIL/ENDUNTIL, SELECT/ENDSELECT, IF/ELSE/END, etc. etc.
  • including the comments before the commands.