Informix Error -683

Reasons / Common Causes

-683 fires when a FOR statement's STEP value, combined with its TO range, would never actually reach the end of the range — per the official guidance's example, FOR i = 10 TO 20 STEP -1 decrements from 10 and can never reach 20, producing what would otherwise be an infinite loop.

1. A negative STEP used with an ascending range (start < end), per the official guidance's example — the step moves the wrong direction to ever reach the endpoint.
2. A positive STEP used with a descending range (start > end), the mirror-image mistake.
3. A STEP sign that was correct when the range's bounds were literals, but became wrong after the range's start/end were changed to variables whose values flipped the intended direction.

Solutions / Resolution

1. Adjust the range or step expression so incremented/decremented values stay within the intended range, per the official guidance — match the STEP sign to the range's direction.
2. For an ascending range (start less than end), use a positive STEP.
3. For a descending range (start greater than end), use a negative STEP.
4. If the range's bounds come from variables, confirm their relative order at runtime, not just at the time the loop was written, since the correct STEP sign depends on their actual values each time the loop runs.

Examples

The disallowed combination

FOR i = 10 TO 20 STEP -1
  ...
END FOR;
-- -683: decrementing from 10 will never reach 20

Corrected

FOR i = 10 TO 20 STEP 1
  ...
END FOR;

A descending range, correctly stepped

FOR i = 20 TO 10 STEP -1
  ...
END FOR;

Diagnostic Checks

1. Compare the range's direction (start vs. end) against the STEP value's sign for every FOR statement, especially when either bound comes from a variable rather than a literal.

Related Errors / Related Topics

• -660 — "Loop variable variable-name cannot be modified." A related FOR-loop restriction, about modifying the loop variable inside the loop.
• -666 — "Variable variable-name must be declared INTEGER or SMALLINT." A related FOR-loop restriction, about the loop variable's declared type.

Match the STEP sign to the range's actual direction — positive for ascending, negative for descending — checked against the bounds' runtime values, not just how the loop was originally written.