You should use a seq. You would not need size as its part of seq as .len.
type
Stack[T] = object
top: int
A: seq[T]
Run
If you NOT going interface with C there is no point in using C style arrays.
BUT if you want to emulate C ... some thing you should not need to do often if
ever you can do it this way:
template `+`[T](p: ptr T, off: int): ptr T =
cast[ptr type(p[])](cast[ByteAddress](p) +% off * sizeof(p[]))
template `[]=`[T](p: ptr T, off: int, val: T) =
(p + off)[] = val
type
Stack[T] = object
top: int
size: int
A: ptr[T]
var stack = Stack[uint16]()
stack.top = 0
stack.size = 2
stack.A = cast[ptr uint16](alloc(sizeof(uint16) * stack.size))
stack.A[0] = uint16 12
stack.A[1] = uint16 12
Run
