has (schema itemName -- hasName)

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.

has (schema itemName -- hasName)

Inputs

schema: Value or Ref whose dereferenced schema is searched for the requested name.

itemName: Known non-NIL Text name being tested for presence.

Outputs

hasName: Known Cond result that is TRUE when at least one matching name exists.

Tests whether the dereferenced schema contains at least one item matching the requested known name.

The name must be known, non-NIL Text. This is a known-name presence test, not a selected-item ordinal lookup. Any matching item makes the result TRUE.

Only the schema participates. Current value contents do not participate.

has uses the same name-matching rules as fieldIndex, but it stops at presence and does not return which ordinal matched.

Behavior

For Dict, the result is TRUE if at least one field has the requested name.

For Dict, duplicate matching names still produce only TRUE; the builtin never reports which ordinal matched.

For Dict, the empty name "" also matches unnamed items.

For List and Tuple, only the empty name "" matches, and it matches only when the Struct object is non-empty.

For all other schemas, the result is FALSE.

Ref values are dereferenced before testing, so a Ref input gives the same result as the referenced schema.

Example

{} () {} [ mixed: { 1 "" def x: 1; y: 2; }; "-- Dict field names --" printCompilerMessage mixed "x" has printStack _:; @mixed "x" has printStack _:; "-- empty name --" printCompilerMessage mixed "" has printStack _:; (1 FALSE) "" has printStack _:; () "" has printStack _:; "-- missing name --" printCompilerMessage mixed "z" has printStack _:; (1 FALSE) "x" has printStack _:; ] "main" exportFunction

Expected Output During Compilation

-- Dict field names -- TRUE TRUE -- empty name -- TRUE TRUE FALSE -- missing name -- FALSE FALSE