从for循环到机器码

def p(*x): print(x)
p(type(range), dir(range))
r = range(2); i = iter(r)
try: p(next(i)); p(next(i)); p(next(i))
except Exception as e: p(e)
def fn():
    n = 0
    for i in range(3): n = n + i
fn()

dis.dis(fn)
(<class 'type'>, [... 'count', 'index', 'start', 'step', 'stop'])
(0,)
(1,)
(StopIteration(),)
7 0 LOAD_CONST 1 (0)
2 STORE_FAST 0 (n)
8 4 LOAD_GLOBAL 0 (range)
6 LOAD_CONST 2 (3)
8 CALL_FUNCTION 1
10 GET_ITER
>> 12 FOR_ITER 12 (to 26)
14 STORE_FAST 1 (i)
16 LOAD_FAST 0 (n)
18 LOAD_FAST 1 (i)
20 BINARY_ADD
22 STORE_FAST 0 (n)
24 JUMP_ABSOLUTE 12
 
mem = [x for x in re.split('[\r|\n]', '''
    store a 1
    store b 2
    add a 1
    add     b -1
    jlz 2
    jmp -3
    jmp 0
'''.lower()) if x != ''] # 刚知道splitlines
# register file: 装register的柜子。register: 登记簿 pc: program counter
reg_file = { 'pc': 0 }
msb = 0 # most significat bit, 符号位
while True:
    instruction = mem[reg_file['pc']] # fetch instruction 取指
    print('"' + instruction + '"', end='\t')
    instruction = instruction.split() # 译码
    op_code = instruction[0] # op: operation
    if op_code == 'store':
        (reg_name, immd) = instruction[1:]
        reg_file[reg_name] = int(immd)
        reg_file['pc'] += 1
    elif op_code == 'add':
        (reg_name, immd) = instruction[1:]
        reg_file[reg_name] += int(immd)
        if reg_file[reg_name] < 0: msb = 1
        reg_file['pc'] += 1
    elif op_code == 'jlz': # jump if less than 0
        immd = int(instruction[1])
        if msb: reg_file['pc'] += immd
        else: reg_file['pc'] += 1
    elif op_code == 'jmp':
        immd = int(instruction[1])
        if immd == 0: break
        reg_file['pc'] += immd
    print('\t', reg_file, ' msb=', msb, sep='')
    input('Press the Enter key')

def bits(n, b = 0): return list(map(lambda x:b,list(range(n))))# 刚知道n*[e]或n*'s'
class ROM:
    def __init__(m):
        m.bytes = (
            ( 0, 0, 0, 0, 0, 0, 0, 1 ), # store a 1
            ( 0, 0, 1, 0, 0, 0, 1, 0 ), # store b 2
            ( 0, 1, 0, 0, 0, 0, 0, 1 ), # add a 1
            ( 0, 1, 1, 1, 1, 1, 1, 1 ), # add b -1
            ( 1, 0, 0, 0, 0, 0, 1, 0 ), # jlz 2
            ( 1, 1, 0, 1, 1, 1, 0, 1 ), # jmp -3
            ( 1, 1, 0, 0, 0, 0, 0, 0 ), # jmp 0
        )
        m.a = m.d = bits(8) # They will have different id() after being assigned
    def read(m): m.d = m.bytes[reduce(lambda hi, low: hi * 2 + low, m.a, 0)]