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IsZero

Function IsZero( const A : Extended): Boolean

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := IsZero(0.0);
end;

Usage​

IsZero tests whether an Extended value is within Velox's calculated default tolerance of zero.

Parameters

NameTypeDescription
AExtended, constValue to compare with zero.

Returns

True when Abs(A) is less than or equal to the calculated tolerance; otherwise False.

Behaviour

The test is tolerant and inclusive. A small nonzero value can therefore return True. It does not inspect the value's bit pattern and it is not equivalent to A = 0.

Important usage notes

  • Win32 and Win64 can classify the same small value differently because their Extended resolutions differ.
  • Positive and negative values are treated symmetrically through Abs.
  • NaN returns False because its absolute value cannot satisfy the comparison.
  • Positive or negative infinity returns False with the finite default tolerance.
  • A value produced by earlier arithmetic may already have rounded differently before it reaches this call.

Usage notes

Use this function for machine-level near-zero checks where Velox's resolution is suitable. Use IsZeroEpsilon when the accepted magnitude is a business or interface rule, and use explicit decimal/minor-unit logic for currency.

Additional Technical Info​

IsZero reports whether an Extended value is within Delphi's calculated default tolerance of zero. Velox calls the Extended overload of System.Math.IsZero through a thin wrapper.

The example returns True. It is source-reviewed and is not executed by the documentation workflow.

Implementation

The Velox wrapper calls System.Math.IsZero(A). With the default epsilon sentinel, the Extended implementation uses ExtendedResolution as the tolerance. Current Delphi defines this as 1E-16 for a true 80-bit Extended and 1E-12 where Extended aliases Double.

Side effects

None.

Errors

There is no normal data-dependent exception. Converting a nonnumeric script value to Extended can raise before the function is called.

Performance and concurrency

The operation is constant-time, allocation-free and re-entrant.

Related entries

  • IsZeroEpsilon supplies the allowed absolute magnitude.
  • CompareValue compares two values using the same default-tolerance family.
  • IsNullorZero performs a different Variant equality operation and must not be treated as equivalent.

External references

Created 2026-07-15