程序员的进化

　　不久前，在互联网上出现了一篇有趣的文章，讲的是对于同一个问题，不同层次的程序员编出的Python代码显示出了不同的风格，代码都很简单，有趣。我把它整理了一下，并修改了几处错误。

编程新手

def factorial(x):
    if x == 0:
        return 1
    else:
        return x * factorial(x - 1)
print factorial(6)

一年编程经验(学Pascal的)

def factorial(x):
    result = 1
    i = 2
    while i <= x:
        result = result * i
        i = i + 1
    return result
print factorial(6)

一年编程经验(学C的)

def fact(x): #{
    result = i = 1;
    while (i <= x): #{
        result *= i;
        i += 1;
    #}
    return result;
#}
print(fact(6))

一年编程经验(读过 SICP)

@tailcall
def fact(x, acc=1):
    if (x > 1): return (fact((x - 1), (acc * x)))
    else:       return acc
print(fact(6))

一年编程经验(Python)

def Factorial(x):
    res = 1
    for i in xrange(2, x + 1):
        res *= i
    return res
print Factorial(6)

懒惰的Python程序员

def fact(x):
    return x > 1 and x * fact(x - 1) or 1
print fact(6)

更懒的Python程序员

f = lambda x: x and x * f(x - 1) or 1
print f(6)

Python 专家

fact = lambda x: reduce(int.__mul__, xrange(2, x + 1), 1)
print fact(6)

Python 黑客

import sys
@tailcall
def fact(x, acc=1):
    if x: return fact(x.__sub__(1), acc.__mul__(x))
    return acc
sys.stdout.write(str(fact(6)) + 'n')

专家级程序员

from c_math import fact
print fact(6)

大英帝国程序员

from c_maths import fact
print fact(6)

Web 设计人员

def factorial(x):
    #-------------------------------------------------
    #--- Code snippet from The Math Vault          ---
    #--- Calculate factorial (C) Arthur Smith 1999 ---
    #-------------------------------------------------
    result = str(1)
    i = 1 #Thanks Adam
    while i <= x:
        #result = result * i  #It's faster to use *=
        #result = str(result * result + i)
           #result = int(result *= i) #??????
        result = str(int(result) * i)
        #result = int(str(result) * i)
        i = i + 1
    return result
print factorial(6)

Unix 程序员

import os
def fact(x):
    os.system('factorial ' + str(x))
fact(6)

Windows 程序员

NULL = None
def CalculateAndPrintFactorialEx(dwNumber,
                                 hOutputDevice,
                                 lpLparam,
                                 lpWparam,
                                 lpsscSecurity,
                                 *dwReserved):
    if lpsscSecurity != NULL:
        return NULL #Not implemented
    dwResult = dwCounter = 1
    while dwCounter <= dwNumber:
        dwResult *= dwCounter
        dwCounter += 1
    hOutputDevice.write(str(dwResult))
    hOutputDevice.write('n')
    return 1
import sys
CalculateAndPrintFactorialEx(6, sys.stdout, NULL, NULL, NULL,
 NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL)

企业级程序员

def new(cls, *args, **kwargs):
    return cls(*args, **kwargs)
  
class Number(object):
    pass
  
class IntegralNumber(int, Number):
    def toInt(self):
        return new (int, self)
  
class InternalBase(object):
    def __init__(self, base):
        self.base = base.toInt()
  
    def getBase(self):
        return new (IntegralNumber, self.base)
  
class MathematicsSystem(object):
    def __init__(self, ibase):
        Abstract
  
    @classmethod
    def getInstance(cls, ibase):
        try:
            cls.__instance
        except AttributeError:
            cls.__instance = new (cls, ibase)
        return cls.__instance
  
class StandardMathematicsSystem(MathematicsSystem):
    def __init__(self, ibase):
        if ibase.getBase() != new (IntegralNumber, 2):
            raise NotImplementedError
        self.base = ibase.getBase()
  
    def calculateFactorial(self, target):
        result = new (IntegralNumber, 1)
        i = new (IntegralNumber, 2)
        while i <= target:
            result = result * i
            i = i + new (IntegralNumber, 1)
        return result
  
print StandardMathematicsSystem.getInstance(new (InternalBase,
new (IntegralNumber, 2))).calculateFactorial(new (IntegralNumber, 6))