[Csnd-dev] for-loop over audio vector

i am testing the for-loop in different situations and found this:

with a while loop i can do
instr 1
   aSin = poscil(1,100)
   kndx = 0
   while (kndx < ksmps) do
     printk2(aSin[kndx])
     kndx += 1
   od
   turnoff
endin

but with a for-loop ...
instr 2
   aSin = poscil(1,100)
   for kndx in aSin do
     printk2(aSin[kndx])
   od
   turnoff
endin
... i get the error:
invalid argument in for statement: found 'aSin', which is not an array

should this not work?