AZK RPG - Controlling Program Workflow

• Do While
•    - do as long as condition is true
•    - LEADING-decision loop (check condition , if true - do)
•    - condition is tested BEFORE the instructions w/i the loop are executed (in "Dow")

• Dow Number < 100;        // check here
•    Number += 1;
•    Sum += Number;
• Enddo;

- File processing with Dow

• Read Customer;
• Dow Not %Eof(Customer);        // %Eof checked here
•    Count += 1;
•    Write Detail;
•    Read Customer;
• Enddo;

Dow - Do While

Dow - Do While

Dow - Do While

• - Do Until
•    - do until condition will become true
•    - TRAILING-decision loop (do at least once, then check condition , if not - do again)
•    - condition is tested AFTER the instructions w/i the loop are executed (in "Enddo")

• Dou Number = 100;
•    Number += 1;
•    Sum += Number;
• Enddo;                // check here

- File processing with Dou

• Dou %Eof(Customer);
•    Read Customer;
•    If %Eof(Customer);
•       Leave
•    Endif;
•    Count += 1;
•    Write Detail;
• Enddo;                // %Eof checked here

Dou - Do Until

Dou - Do Until

Dou - Do Until

• - count-controlled loop
• Processing will be done 25 times

• For Counter = 1 To 50 By 2;
•    ...
• Endfor;

• - if the value to be stored is too large for the result field
• - run-time error
• - program stops and display an error message

• Zoned(3.2) + Zoned(6.3)
• result must be (6+1) Zoned(7.3)

• Zoned(5.2) * Zoned(4.2)
• result must be (5+4) (2+2) Zoned(9.4)

- if you divide by value less than 1, manually calculate with some representative values to get a sense of the size required to store result

- ILE RPG automatically and w/o warning truncates extra decimal positions to fit the value in the result decimal positions

- Sequential Access

Read file-name {datastructure};

• Dcl-f Customer Disk;
•      // - result DS MUST use Likerec keyword
• Dcl-ds Custdata Likerec(Custrec);

• Read Customers;
• If %Eof(Customers);
•      // End of file processing
• Endif;

•      // - transfers data from file Customer to DS Custdata
• Read Customers Custdata;
• If %Eof(Customers);
•      // End of file processing
• Endif;

- For program-described files, the DS's length must be same as file's record length

• - To position to first record (w/o reading)
• - To check if record exists w/o reading the record

•      // To position to first record (w/o reading)
• Setll search-argument file-name

• Setll *Loval Customers;
• Read Customers;        // Read firs record

•      // To check if record exists w/o reading the record
• Setll Custchk Customers;
• If %Equal(Customers);
•    Exsr Validcust;        // cusromer exists
• Else;
•    Exsr Invalidcust;   // record not found
• Endif;

• - Sequential Access
• - read equal key
• - usually used w Setll

Reade search-argument file-name {DS};

DS - result DS to receive the data (optional)

• Setll Indate Orders;
•    . . .
• If %Equal(Orders);
•    Reade Indate Orders;

•    Dow Not %Eof(Orders);
•       Write Orderline;
•       Reade Indate Orders;
•    Enddo;

• Else;
•    Exsr Noorders;
• Endif;

• - Read prior record
• Readp file-name {DS};

Readp Orders;

- Read prior equal

Readpe search-argument file-name {DS};

Readpe Indate Orders;

- To read last record

• Setgt *Hival Customers;
• Readp Customers;    // Read last record

- to determine the next order number to use

• Setgt *Hival Orders;
• Readp Orders;
• If Not %Eof(Orders);     // last record found
•    Ordernbr += 1;    
• Else;             // no last record (empty file)
•    Ordernbr = 1;
• Endif;

• - Random Access
• - To position to record (with reading)

Chain Indate Orders;

• Chain Indate Orders;
•    . . .
• If %Found(Orders);
•    Dow Not %Eof(Orders);
•       Write Orderline;
•       Reade Indate Orders;
•    Enddo;
• Else;
•    Exsr Noorders;
• Endif;

Chain (Company:Region:Custno) Customers;

Chain ('346' : Region : %Char(Lastcustno + 1)) Customers;

- we can use partial composite keys

Chain (Company:Region) Customers;

- to specify Key DS (same as KEYLIST)

%Kds(datastructure {:numb-of-keys})

• - use 'datastructure' as the search argument of a composite key
• - 'numb-of-keys' - to specify # of keys to use (partial key)

• - DS to be used in %Kds
•      Dcl-ds Custkeys;
•         Company Char(3);
•         Region Char(3);
•         Custno Char(9);
•      End-ds;

• - Ext DS with "Extname" or "Likerec" keyword that automatically extrats only the key fields from the record format 
•      Dcl-ds Custkeys Ext Extname('CUSTOMERS':*Key) End-ds;
•      Dcl-ds Custkeys Likerec(Custrec:*Key) End-ds;

• - Chain using all keys of Custkeys DS
•      Chain %Kds(Custkeys) Customers;

• - Chain using only 2 of 3 keys of Custkeys DS
•      Chain %Kds(Custkeys:2) Customers;

• Dcl-ds Custkeys;
•    Company Char(3);
•    Region Char(3);
•    Custno Char(9);
• End-ds;
•    . . .
• Chain %Kds(Custkeys) Customers;

• - Random Access
•     
• Write file-name {DS};

• - DS - datastructure
•    - must be specified for Prog Desc File
•    - optional for Ext Desc File

• Dcl-f Customers Disk Usage(*Output);
• Dcl-ds Custdata Likerec(Custrec:*Output);

•             RF        DS
• Write Custrec Custdata;

• - Write transfers data from DS to the record
• - Custsrec - Rec Format of Customer file
• - Custdate - DS name

• - modifies the record most recently read from an update file
• - rewrites ALL of the a database record's fields to the file

Update file-rec-name {DS);

• Dcl-f Customers Dick Uage(*Update);
•         . . .
•    Chain Custno Customers;      
•    If %Found(Customers):
•        BalanceDue += InvoiceAmt;
•        LastDate = InvoiceDate;
•        Update Custrec;
•    Else;
•        Exsr NoCustomer;
•    Endif;

• Dcl-ds CustData Likerec(Custrec:*Input);
•      . . .
•         Chain Custno Customers;
•         
•         If %Found(Customers):
•             BalanceDue += InvoiceAmt;
•             LastDate = InvoiceDate;
•             Update Custrec Custdata;
•         Else;
•             Exsr NoCustomer;
•         Endif;

• Dcl-f Customers Dick Uage(*Update);
•         . . .
•    Chain Custno Customers;      
•    If %Found(Customers):
•        BalanceDue += InvoiceAmt;
•        LastDate = InvoiceDate;
•        Update Custrec %Fields(BalanceDue:LastDate);
•    Else;
•        Exsr NoCustomer;
•    Endif;

Delete {seach-argument} file-name;

• Chain Custno Customers;        // retrieve record
•    . . .
• If %Found(Customers);
•    Delete Customers;    // delete retrieved record
• Endif;

• Delete Custno Customers;    // retrieve record
•                         // delete first and only one record
•                         // with specified Custno

• - Two programs cannot access the same record in update mode
•      - To Update the record use Chain, Read..., locking the record
•      - W/o updating, use Chain(n), Read(n)..., w/o locking the record

Chain Custno Customers;        // - LOCKS the record

Chain(n) Custno Customers;    // - does NOT LOCK the record

Unlock Customers;        // - UNLOCK the record

• - Usropn keyword
• - 'User Open' to use Open and Close File in program

Dcl-f Customers Disk Usropn;    // - to use Open and Close File in program

Open Customers;            // - if Customer already opened - ERROR

• If Not %Open(Customers);    // - to check if Customers is already opened
•    Open Customers;
• Endif;

Close Customers;        // - if Customer already closed - NO Error

Close *All;            // - close all opened files