RPG Arrays

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Let's explore how arrays in modern free-form RPGLE can be searched, sorted, and used in embedded SQL fetches. These techniques elevate your RPGLE code with cleaner logic and performance optimization.

1. Searching Arrays

RPGLE provides built-in functions for efficient array searching:

A. %LOOKUP — For Unsorted Arrays

Use this when you have an unsorted array and need to find the index of an exact value.

**FREE
Dcl-S Codes   Char(5) Dim(5) Inz('A100':'B200':'C300':'D400':'E500');
Dcl-S Target  Char(5) Inz('C300');
Dcl-S idx     Int(3);

idx = %LOOKUP(Target: Codes);

If idx > 0;
   Dsply ('Found at position: ' + %Char(idx));
Else;
   Dsply ('Value not found');
Endif;

*InLR = *On;
Return;

  • %LOOKUP returns the position (1‑based) if found, or 0 otherwise.

B. %SEARCH — For Pattern Matching

Perfect for when you're looking for a substring or pattern in character arrays.

**FREE
Dcl-S Messages Char(30) Dim(3) Inz('Error 404':'OK 200':'Warning 300');
Dcl-S position  Int(3);

position = %SEARCH('200': Messages);
If position > 0;
   Dsply ('"200" found in: ' + Messages(position));
Endif;

2. Sorting Arrays

A. Compile-Time Sorted Arrays (ASCEND / DESCEND)

Sort your arrays at compile time automatically:

**FREE
Dcl-S AlphaCodes Char(5) Dim(5) Ascend Inz('D400':'B200':'E500':'A100':'C300');

Dsply ('First code after sort: ' + AlphaCodes(1)); // Displays 'A100'

B. Run-Time Sorting via RPGLE Utilities

For dynamic sorting, IBM i provides QSort in the qsort service program. Here's a simplified use:

**FREE
Dcl-S Numbers   Packed(5:0) Dim(10);
// Initialize array...
// Call QSort (requires prototype definitions)
QSort(pArray: %Elem(Numbers): %Size(Numbers:*): *Off);

// Now Numbers is sorted

(Note: You'll need to define the QSort prototype or use a sorting service program like QUSRSORT.)

3. Using Arrays with Embedded SQL Fetch

In RPGLE versions with embedded SQL, it's possible to fetch multiple rows into an array—a useful technique when you need to retrieve a limited dataset into memory.

Example: FETCH INTO Array (IBM i 7.3 TR7, 7.4 TR1+)

**FREE
exec sql
  set option commit = *NONE;

Dcl-S CustNames  Char(50) Dim(100);
Dcl-S Counter    Int(10)   Inz(0);

exec sql
  declare C1 cursor for
    select name from customers
    where city = 'PARIS'
    order by name
    fetch first 100 rows only;

exec sql
  open C1;

dow Counter < %Elem(CustNames);
  exec sql
    fetch next from C1 into :CustNames(Counter + 1);
  if sqlcode = 0;
    Counter += 1;
  else;
    leave;
  endif;
enddo;

exec sql close C1;

for i = 1 to Counter;
  Dsply 'Customer ' + %Char(i) + ': ' + CustNames(i);
endfor;

*InLR = *On;
Return;

This example shows:

  • A cursor that retrieves ordered customer names.

  • Fetching each name into the CustNames array.

  • Stopping when no more rows match or the array is full.

Summary Table

Scenario Technique Key Functionality
Exact search in array %LOOKUP Finds position of exact match
Pattern search %SEARCH Matches substring or pattern
Compile-time sorting ASCEND / DESCEND in declaration Automatically orders array at compile time
Run-time sorting QSort (or equivalent) Sorts any array during execution
Bulk SQL fetch into array Embedded SQL with cursor and array fetch Efficiently loads multiple DB rows

 

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