fieldIsRef (schema ordinal -- isRefLike)

Builtins

Name introduction, declaration modifiers, and module binding: NAME: ...;, codeRef, def, exportFunction, importFunction, importVariable, overload, private, static, use, and virtual.
Struct construction forms: (...), {...}, and array.
Selection forms: source-text selection with NAME and .NAME, read-only source-text selection with @NAME and .@NAME, and ordinal or known-name data-input selection with @, callField, and fieldRead.
Writing forms: source-text selection with !NAME and .!NAME, ordinal selection with ! and fieldWrite, and already-selected destination replacement with set.
Calling and control flow: call, if, loop, ucall, and uif.
Text operations: &, LF, attribute, textSize, and textSplit.
Condition constants, value comparison, and logical operators: <, =, >, DEBUG, FALSE, TRUE, and, is, lshift, or, rshift, xor, and ~.
Arithmetic and numeric transforms: *, +, -, /, ^, cast, ceil, cos, floor, log, log10, mod, neg, sin, and sqrt.
Reference, creation, and value-state operations: const, dynamic, isConst, isDirty, isDynamic, isRef, isStatic, known?, new, newVarOfTheSameType, stable?, unconst, and unknownStable?.
Schema and struct introspection: code?, codeRef?, fieldCount, fieldIndex, fieldIsRef, fieldIsVirtual, fieldName, has, isCombined, managed?, same, schemaName, and virtual?.
Storage and manual lifetime operations: addressToReference, alignment, manuallyDestroyVariable, manuallyInitVariable, storageAddress, and storageSize.
Diagnostics and compile-time failure: failCompilation, getCallTrace, printCompilerMessage, printStack, printStackTrace, and raiseStaticError.

fieldIsRef (schema ordinal -- isRefLike)

Inputs

schema: Value or Ref whose dereferenced schema is Struct and whose selected item is tested.

ordinal: Zero-based item ordinal being tested.

Outputs

isRefLike: Known Cond result that is TRUE when the selected item schema is Ref-like.

fieldIsRef is a selected-item schema predicate. It tests whether one selected item of the dereferenced Struct schema is Ref-like.

In this builtin, Ref-like means Ref, Code, or Text. Current field contents, current knownness, and current NIL status do not participate. This is a schema predicate, not a read-result predicate, so a non-static In-place item can make fieldIsRef return FALSE even though reading that item later produces a Ref-like result. A static Ref-like item can make both fieldIsRef and fieldIsVirtual return TRUE, because schema kind and runtime storage are tested separately.

Behavior

The result is always known.

ordinal is a zero-based known Int32 selected-item ordinal.

TRUE means that the selected item schema is Ref, Code, or Text.

Text and Code item schemas still report TRUE when a current runtime value would be unknown or NIL.

A static Ref-like item can make both fieldIsRef and fieldIsVirtual report TRUE.

All other item schemas, including In-place and Meta, report FALSE.

The result depends only on the selected item schema, not on the item name or current field contents.

If ordinal is out of bounds for the Struct schema, the builtin raises a compilation error.

Example

{} 0 {} [ dict: { ordinaryField: 0; textField: 0 ("") dynamic @; codeField: {} () {} codeRef; metaField: (); }; "-- In-place field schema versus read result --" printCompilerMessage dict 0 fieldIsRef printStack _:; @dict 0 fieldRead isRef printStack _:; _:; "-- text field schema versus read result --" printCompilerMessage dict 1 fieldIsRef printStack _:; @dict 1 fieldRead isRef printStack _:; _:; "-- code field schema versus read result --" printCompilerMessage dict 2 fieldIsRef printStack _:; @dict 2 fieldRead isRef printStack _:; _:; "-- meta field schema versus read result --" printCompilerMessage dict 3 fieldIsRef printStack _:; @dict 3 fieldRead isRef printStack _:; _:; tuple: (0 "" {} () {} codeRef); "-- Tuple item schemas use the same category --" printCompilerMessage tuple 0 fieldIsRef printStack _:; tuple 1 fieldIsRef printStack _:; tuple 2 fieldIsRef printStack _:; 0 ] "main" exportFunction

Expected Output During Compilation

-- In-place field schema versus read result -- FALSE 0 Ref TRUE -- text field schema versus read result -- TRUE Text TRUE -- code field schema versus read result -- TRUE {} () {} codeRef CNIL TRUE -- meta field schema versus read result -- FALSE () FALSE -- Tuple item schemas use the same category -- FALSE TRUE TRUE