>(sizeof 'RECT)
=>16
>(sizeof 'RECT 'left)
=>4
>(typeof 'RECT)
=>(RECT (LONG left) (LONG top) (LONG right) (LONG bottom))
>(typeof 'RECT 'left)
=>(LONG 4)
>(offsetof 'RECT 'top)
=>4
こういうのあったら便利だと思うけど、どう？