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Exclude

procedure Exclude;

Example​

procedure ScriptEvent(var Value: variant);
var
  Options: TLocateOptions;
begin
  Options := [loCaseInsensitive, loPartialKey];
  Exclude(Options, loPartialKey);

  Value := not (loPartialKey in Options); // True
end;

Usage​

Exclude removes one byte-encoded member from a mutable Velox scripting set by clearing its ordinal bit.

Effective call syntax

Exclude(var S, Member);

Parameters

NameEffective modeDescription
Svar/in-outSet variable to mutate. It must be an assignable variable, not a set literal, property result or expression.
MemberinputMember whose ordinal bit is cleared. For safe use, its type must be exactly the base enumeration or Byte type of S, and its value must be in that set's declared range.

There is no return value. Test membership with Member in S after the call if later logic needs to observe the state.

Additional Technical Info​

Exclude mutates an existing PascalScript set variable by clearing the bit for one enumeration or Byte member. If the member is already absent, the set remains unchanged. The function does not allocate or return a new set.

The generated Code Library declaration is incomplete: the modified PascalScript compiler creates the parameterless declaration first and then programmatically injects two required, untyped parameters. Real scripts must use the two-argument form shown in the example. The example is fictional and source-reviewed only.

Generated declaration

Implementation

At compile time, S is injected as an untyped pmInOut parameter and Member as an untyped pmIn parameter. The compiler enforces only that S is a variable; because neither injected parameter declares a type, it does not prove that S is a set or that Member belongs to the set's base type.

At runtime, the modified PascalScript Exclude_ handler:

  1. requires the first value's runtime base type to be btSet;
  2. requires the member's runtime base type to be btU8;
  3. reads the member as an unsigned byte ordinal;
  4. selects byte Ordinal shr 3; and
  5. clears bit Ordinal and 7 using bitwise AND-NOT.

Small enumerations are exported to the runtime as btU8, so ordinary enum-set use such as TLocateOptions works. A set of Byte also meets the terminal types.

Idempotence and state

Clearing an already-clear bit is harmless and produces the same set. The procedure changes only the supplied variable's bit storage. It does not log, change a dataset, set flow status or affect another set value that was copied before the call.

The mutation is not synchronised. Do not arrange for concurrent script executions to mutate the same externally shared set storage without an ownership/locking design. Ordinary local variables and per-object properties owned by one execution do not introduce that sharing by themselves.

Character-set incompatibility

PascalScript permits set types whose base is Char, and Velox exposes TvxChars and TvxSeparators. However, a character argument retains runtime type btChar, while Exclude_ accepts only btU8. Consequently, the natural call below can compile but fails when the external runtime handler is called:

// Do not use: the current runtime rejects the btChar member.
Exclude(Separators, ',');

For a character set, use a same-typed set expression instead:

Separators := Separators - [','];

This is a current modified-PascalScript implementation defect, not Delphi System.Exclude behaviour.

Critical range and type hazard

The runtime verifies the broad storage classes but never verifies that the byte member belongs to this particular set or is below the set's bit size. Enumeration sets often occupy fewer than 32 bytes. Passing a Byte or a member of an unrelated small enum can therefore compile and pass the runtime btU8 test.

If that ordinal exceeds the set's last bit, Exclude_ indexes beyond the allocated set storage and writes there without a range check. This can corrupt adjacent PascalScript stack data rather than producing a clean “member out of range” error. Never use integer casts, arbitrary bytes, unrelated enumerations or unvalidated ordinals as Member; use a value of the exact base type of S.

For wrong broad runtime types—such as a non-set first argument or Char member—the handler returns False and PascalScript reports that it could not call the procedure. There is no special Velox recovery or diagnostic added around it.

Related entries

  • Include sets the corresponding membership bit and has the same compiler/runtime limitations.

External references

Created 2026-07-15