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Random

function Random: Extended;

Example​

procedure ScriptEvent(var Value: variant);
begin
  Value := Random; // pseudo-random Extended from 0 inclusive to 1 exclusive
end;

Usage​

Random advances Velox's shared across the Velox process linear-congruential generator and returns an Extended value in [0,1).

Parameters

Random has no parameters. It can be called without parentheses.

Returns

One of 2^32 possible values formed as the next unsigned 32-bit generator output multiplied by 2^-32. Zero is possible; one is not.

Additional Technical Info​

Random returns the next pseudo-random floating-point value from Delphi's process-global generator. The result is greater than or equal to zero and strictly less than one.

This generator is deterministic, shared and non-cryptographic. It is suitable for low-risk sampling/test variation where sequence coupling is acceptable, not for passwords, tokens, identifiers, security decisions or independent concurrent simulations. The example is fictional and source-reviewed only.

Implementation

  1. uPSI_vxCommonNumber registers vxCommonNumber.Random directly.
  2. The wrapper calls no-argument Delphi System.Random.
  3. Installed DefaultRandom32 advances global RandSeed with the linear-congruential recurrence seed := seed * $08088405 + 1 modulo 2^32.
  4. Delphi converts the unsigned output to floating point and multiplies it by 2^-32.

Random32Proc can theoretically be replaced by host code, but Velox does not replace it in the reviewed source; the installed default above is the effective implementation.

State, sequence and concurrency

  • Every call advances the same process-global RandSeed. Randomize replaces that state using timing, while RandomizeSeed assigns an explicit state.
  • Other scripts/flows in the same Designer, Service or API Service process can change the sequence between two calls.
  • The update is not protected by a lock. Concurrent calls can race and sequence behavior should not be treated as reproducible or independently partitioned.
  • A process restart begins from RTL initialization state until a reseed occurs.
  • The algorithm and 32-bit internal state are unsuitable for cryptographic unpredictability.

Precision and target behaviour

The public return type is Extended, but the scale constant is a Double and the entropy is only 32 bits. Win64 aliases Extended to Double; Win32 may carry the scaled value in wider precision, but that does not create more random states.

Side effects

The only direct side effect is mutation of process-global pseudo-random state. There is no log, database write or operating-system entropy read per call.

Related entries

  • RandomInt maps this value to an inclusive rounded Integer range with a biased distribution.
  • Randomize timing-seeds the shared generator.
  • RandomizeSeed establishes a repeatable sequence only when no other shared random call intervenes.

External references

Created 2026-07-15