fieldIndex (schema itemName -- ordinal)

Inputs

• schema: Object or Ref whose dereferenced schema is Struct and whose item names are searched by itemName.
• itemName: Known non-NIL Text item name used for selection.

Outputs

• ordinal: Known Int32 ordinal of the selected item.

Returns the selected item ordinal for a known, non-NIL Text item name in the dereferenced Struct schema; name-based field selection uses the same last-match rule as .NAME.

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

Use fieldName to preserve the exact stored name at one ordinal and has for presence-only testing.

Behavior

• For Dict, the last item whose name matches itemName is selected.
• For Dict, the empty name "" also matches unnamed items and selects the last unnamed item when one is present.
• For List and Tuple, only the empty name "" is valid, and it selects the last item.
• For an empty List or Tuple, no name is valid, including "".
• If no matching item exists, the builtin raises a compilation error.

Example

{} 0 {} [
  mixed: { 1 "" def 2 "" def 3 "x" def 4 "x" def };

  "-- fieldIndex returns the last match --" printCompilerMessage
  virtual emptyKey: mixed "" fieldIndex;
  emptyKey printStack _:;
  mixed emptyKey fieldName printStack _:;
  virtual xKey: mixed "x" fieldIndex;
  xKey printStack _:;
  mixed xKey fieldName printStack _:;

  "-- earlier matches still exist --" printCompilerMessage
  mixed fieldCount printStack _:;
  mixed 0 fieldName printStack _:;
  mixed 2 fieldName printStack _:;

  "-- Tuple unnamed item --" printCompilerMessage
  virtual tupleKey: (1 FALSE) "" fieldIndex;
  tupleKey printStack _:;
  (1 FALSE) tupleKey fieldName printStack _:;

  0
] "main" exportFunction

Expected Output During Compilation

-- fieldIndex returns the last match --
1
""
3
"x"
-- earlier matches still exist --
4
""
"x"
-- Tuple unnamed item --
1
""

See also

• fieldCount builtin (schema -- itemCount) Schema item count and valid ordinal-range upper bound.
• fieldIsRef builtin (schema ordinal -- isRefLike) Ref-like test for one selected item schema.
• fieldIsVirtual builtin (schema ordinal -- hasNoStorage) No-storage test for one selected item.
• fieldName builtin (schema ordinal -- itemName) Ordinal-to-name lookup that preserves the stored name at one selected ordinal.
• has builtin (schema itemName -- hasName) Known-name presence test that does not choose an ordinal.
• schemaName builtin (schema -- reportedName) Reported name of the dereferenced schema.