// Test INDEX ON with User Defined Functions
PROCEDURE Main()
   LOCAL i, aStruct, aCit, nCidx

   aStruct := {{"ID","N",6,0}, {"NAME","C",20,0}, {"CITY","C",15,0}}
   dbCreate("udf_test", aStruct)
   USE "udf_test" NEW

   aCit := {"Seoul","Tokyo","Beijing"}
   FOR i := 1 TO 10
      APPEND BLANK
      REPLACE ID   WITH i
      REPLACE NAME WITH PadR("Name_" + PadL(LTrim(Str(i)), 3, "0"), 20)
      nCidx := Int((i-1) % 3) + 1
      REPLACE CITY WITH PadR(aCit[nCidx], 15)
   NEXT
   ? "Records:", RecCount()

   // Test 1: INDEX ON with built-in function (baseline)
   INDEX ON UPPER(NAME) TO udf_idx1
   GO TOP
   ? "T1 UPPER top:", RTrim(FieldGet(2)), RecNo()
   SEEK PadR("NAME_005", 20)
   ? "T2 UPPER seek:", Found(), RecNo()

   // Test 2: INDEX ON with UDF
   INDEX ON MyKey(FIELD->NAME) TO udf_idx2
   GO TOP
   ? "T3 UDF top:", RTrim(FieldGet(2)), RecNo()
   SEEK PadR("KEY:Name_001", 20)
   ? "T4 UDF seek:", Found(), RecNo()

   // Test 3: INDEX ON with two-param UDF
   INDEX ON CityKey(FIELD->CITY, FIELD->NAME) TO udf_idx3
   GO TOP
   ? "T5 UDF2 top:", RTrim(FieldGet(3)), RTrim(FieldGet(2)), RecNo()

   // Test 4: Nested: built-in wrapping UDF
   INDEX ON Left(MyKey(FIELD->NAME), 15) TO udf_idx4
   GO TOP
   ? "T6 Nested top:", RTrim(FieldGet(2)), RecNo()

   CLOSE ALL
   ? "DONE"
RETURN

FUNCTION MyKey(cName)
   LOCAL cResult
   cResult := "KEY:" + RTrim(cName)
RETURN PadR(cResult, 20)

FUNCTION CityKey(cCity, cName)
   LOCAL cResult
   cResult := RTrim(cCity) + ":" + RTrim(cName)
RETURN PadR(cResult, 30)