virtual? (schema -- isMeta)

Inputs

• schema: Object or Ref whose dereferenced schema is tested for Meta status.

Outputs

• isMeta: Known Cond result that is TRUE when schema dereferences to Meta.

The name is historical. virtual? is a dereferenced-schema predicate. It tests whether the dereferenced schema is Meta.

It does not test whether an object or item was declared with virtual or whether a selected Struct item lacks runtime field storage. A static item can therefore make fieldIsVirtual return TRUE while a later read of that item makes virtual? return FALSE.

Ref inputs are followed before the test. Current value contents do not participate.

Example

{} 0 {} [
  virtual staticLocal: 0;
  dict: {
    ordinaryField: 0;
    staticField: 0 virtual;
    metaField: ();
  };

  "-- In-place field read result --" printCompilerMessage
  @dict 0 fieldRead virtual? printStack _:;
  dict 0 fieldIsVirtual printStack _:;

  "-- static field read result --" printCompilerMessage
  @dict 1 fieldRead virtual? printStack _:;
  dict 1 fieldIsVirtual printStack _:;

  "-- meta field read result --" printCompilerMessage
  @dict 2 fieldRead virtual? printStack _:;
  dict 2 fieldIsVirtual printStack _:;

  "-- value declared with virtual is still not meta --" printCompilerMessage
  staticLocal virtual? printStack _:;

  0
] "main" exportFunction

Expected Output During Compilation

-- In-place field read result --
FALSE
FALSE
-- static field read result --
FALSE
TRUE
-- meta field read result --
TRUE
TRUE
-- value declared with virtual is still not meta --
FALSE

See also

• alignment builtin (schema -- alignment) Returns the storage alignment requirement of the dereferenced schema.
• fieldIsVirtual builtin (schema ordinal -- hasNoStorage) Selected-item storage predicate for one Struct item.
• virtual builtin (--) Historical static-declaration modifier for the next local.
• code? builtin (schema -- isBlock) Historical Block dereferenced-schema test.
• codeRef? builtin (schema -- isCode) Code dereferenced-schema test.
• isCombined builtin (schema -- isCombined) Struct-group dereferenced-schema test.
• managed? builtin (schema -- isManaged) Managed-lifetime dereferenced-schema test.
• same builtin (leftSchema rightSchema -- isSameSchema) Exact dereferenced-schema equality test.
• schemaName builtin (schema -- reportedName) Reported name of the dereferenced schema.
• storageSize builtin (schema -- size) Returns the storage size of the dereferenced schema.