Function UpValueId

lua.go:1303–1311

UpValueId returns a unique identifier for the upvalue numbered n from the closure at index f. Parameters f and n are as in UpValue (but n cannot be greater than the number of upvalues). These unique identifiers allow a program to check whether different closures share upvalues. Lua closures that sh

(l *State, f, n int)

// access a same external local variable) will return identical ids for those
// upvalue indices.
func UpValueId(l *State, f, n int) interface{} {
	switch fun := l.indexToValue(f).(type) {
	case *luaClosure:
		return *l.upValue(f, n)
	case *goClosure:
		return &fun.upValues[n-1]
	}
	panic("closure expected")
}

// UpValueJoin makes the n1-th upvalue of the Lua closure at index f1 refer to
// the n2-th upvalue of the Lua closure at index f2.