def reduce_stack(self, stack, pre):
"""
Compose instruction tuple
:param stack: list of parsed instruction components
:param pre: True if instruction has prefix operator
"""
sl = len(stack)
stack = stack[:1] + \
(stack[::-1][1:-1] if isinstance(self, parseX86) else stack[1:-1]) + \
stack[-1:] + [pre]
if sl == 2: return Types.SingleInstr(stack)
elif sl == 3: return Types.DoubleInstr(stack)
elif sl == 4: return Types.TripleInstr(stack)
elif sl == 5: return Types.FourInstr(stack)
elif sl == 6: return Types.FiveInstr(stack)
elif config.arch == config.ARCH_ARMT and sl == 8: return Types.CoproInstr(stack)
raise Exception('Parsing error, strange number of tokens: ' + str(sl))
