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Round

function Round(E: Extended): LongInt;

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := Round(2.5); // normally 2 under nearest/even rounding
end;

Usage​

Rounds an Extended value to the nearest 32-bit LongInt using the active floating-point rounding mode.

Parameters

NameTypeDescription
EExtendedFloating value to round according to the active x87/SSE rounding mode.

Returns

For a Velox-rounded value within Low(LongInt)..High(LongInt), the expected 32-bit integer. Values outside that range but still within Int64 silently wrap modulo 2^32 because Velox scripting.inc disables range/overflow checks in DefProc.

Velox Int64 resultVelox LongInt result
21474836472147483647
2147483648-2147483648
4294967295-1
42949672960

Additional Technical Info​

Round rounds an Extended value to an integer using Delphi System.Round, then stores only a PascalScript 32-bit LongInt result.

The default floating-point mode is nearest with ties to even (2.5 -> 2, 3.5 -> 4), but the wrapper does not force that mode. Its 32-bit unchecked narrowing is materially different from Delphi's documented Int64 result. The example is fictional and source-reviewed only.

Implementation

  1. The modified PascalScript compiler declares Round in the Numeric group.
  2. Runtime DefProc selector 18 reads an Extended from the stack.
  3. Delphi System.Round produces an Int64 according to the active floating-point mode.
  4. Passing that value to Stack.SetInt narrows it to LongInt with checks explicitly disabled.

Edge cases and errors

  • Default midpoint behavior is nearest/even, not always away from zero.
  • Code elsewhere in the process can change the floating-point rounding mode, altering results; Velox does not restore a known mode around this call.
  • NaN, infinity or a rounded value outside Delphi's Int64 conversion range can raise EInvalidOp/a math error before the 32-bit narrowing.
  • Extended is Double on default Win64 and wider on Win32, so borderline values can differ by target.
  • Do not use this function as a checked conversion. Validate the 32-bit range before calling if wraparound is unacceptable.

Related entries

  • Trunc discards the fraction toward zero and has the same unchecked 32-bit narrowing.
  • Round2BR scales a Double and uses Delphi Round before rescaling.
  • Round2Up implements midpoint-away-from-zero behavior through text for supported inputs.

External references

Created 2026-07-15