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AL gives no short-circuit (lazy) evaluation guarantee for and/or/xor — neither the AL operators nor the boolean operators documentation defines a lazy evaluation order. LLMs trained on C#, JavaScript, or SQL assume the left operand guards the right, which produces conditions where a guard does not protect an unsafe subscript or a field read after a failed Get, and where an expensive operand is paid on every path. Adds community/knowledge/performance/boolean-operators-do-not-short-circuit.md with good/bad AL companions. The guidance prefers nested if when one operand depends on another, while keeping and/or legitimate for operands that are independently safe and cheap, so a reviewer does not flag harmless bound checks. This is the first article in a community performance domain; the Microsoft performance review leaf skill already sources candidates by domain across every enabled layer, so no skill change is needed to reach it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
24 lines
918 B
AL
24 lines
918 B
AL
codeunit 50540 "Perf Sample NoShortCircuit Good"
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{
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procedure ExceedsThreshold(var Thresholds: array[10] of Decimal; Index: Integer; Amount: Decimal): Boolean
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begin
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// 'and' is safe here: both operands are cheap and neither depends on the other.
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if (Index >= 1) and (Index <= ArrayLen(Thresholds)) then
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// The subscript lives in its own if, so it is never evaluated out of range.
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if Amount > Thresholds[Index] then
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exit(true);
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exit(false);
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end;
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procedure IsBlockedCustomer(CustomerNo: Code[20]): Boolean
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var
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Customer: Record Customer;
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begin
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// The cheap test runs first, and the field is read only after Get succeeded.
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if CustomerNo = '' then
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exit(false);
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if not Customer.Get(CustomerNo) then
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exit(false);
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exit(Customer.Blocked <> Customer.Blocked::" ");
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end;
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}
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