// Five Go Extensions — All 9 new syntax features
IMPORT "strings"
IMPORT "fmt"

PROCEDURE Main()
   LOCAL cName, nAge, cResult, cUpper, cCity
   LOCAL aData, aSub, i
   LOCAL db, err

   cName := "Charles"
   nAge := 30
   cCity := "Seoul"

   ? "=== Five Go Extension Syntax ==="
   ?

   // 1. Multi-Return: a, b := Func()
   ? "[1] Multi-Return"
   cUpper, cResult := strings.ToUpper("hello"), strings.ToLower("WORLD")
   ? "  upper:", cUpper, " lower:", cResult

   // 2. DEFER — auto cleanup
   ? "[2] DEFER"
   TestDefer()

   // 3. Slice syntax: a[low:high]
   ? "[3] Slice"
   aData := {"alpha", "beta", "gamma", "delta", "epsilon"}
   aSub := aData[2:4]
   ? "  aData[2:4]:", aSub[1], aSub[2]
   aSub := aData[3:]
   ? "  aData[3:]:", aSub[1], aSub[2]
   aSub := aData[:2]
   ? "  aData[:2]:", aSub[1]

   // 4. Parallel assignment: a, b := b, a
   ? "[4] Parallel / Swap"
   cUpper, cResult := cResult, cUpper
   ? "  swapped:", cUpper, cResult

   // 5. Blank identifier _
   ? "[5] Blank _"
   _, cResult := "discard", "keep"
   ? "  _,keep:", cResult

   // 6. SWITCH (existing + compatible)
   ? "[6] SWITCH"
   SWITCH nAge
   CASE 20
      ? "  twenty"
   CASE 30
      ? "  thirty"
   OTHERWISE
      ? "  other"
   ENDSWITCH

   // 7. CONST block
   ? "[7] CONST"
   CONST
      STATUS_ACTIVE := 1
      STATUS_CLOSED := 2
      STATUS_PENDING := 3
   END CONST
   ? "  CONST defined"

   // 8. Nil-safe: obj?:Method()
   ? "[8] Nil-safe ?:"
   db := NIL
   cResult := db?:Close()
   ? "  nil?:Close():", cResult, "(no crash!)"

   // 9. String interpolation: f"..."
   ? "[9] f-string"
   cResult := f"Name: {cName}, Age: {nAge}, City: {cCity}"
   ? " ", cResult

   ?
   ? "=== All Extensions OK ==="

   RETURN

PROCEDURE TestDefer()
   LOCAL cStatus
   cStatus := "open"
   DEFER QOut("  [defer] cleanup!")
   cStatus := "processing"
   ? "  working..."
   cStatus := "done"
   RETURN