函数式编程

一个Python实现24点的程序，看不懂，但是激发了学习下的兴趣

funs = [ lambda x, item: (x+item[0],
                               str(x)+'+('+item[1]+')'
                              ),
      lambda x, item: (x-item[0],
                               str(x)+'-('+item[1]+')'
                              ),
      lambda x, item: (item[0]-x,
                               '('+item[1]+')-'+str(x)
                              ),
      lambda x, item: (x*item[0],
                               str(x)+'*('+item[1]+')'
                              ),
      lambda x, item:   (item[0]==0 and (0,'ZZZ')) or \
                        (x/item[0],
                               str(x)+'/('+item[1]+')'
                              ),
      lambda x, item:   (x==0 and (0,'ZZZ')) or \
                        (item[0]/x,
                               '('+item[1]+')/'+str(x)
                              )
]

def con(num):
    l = len(num)
    p = list()
    if l==1: return {num[0]:str(num[0])}
    for i in range(l):
        for f in funs:
            p += map(lambda item: f(num[i],item),
                       con(num[:i]+num[i+1:]).items()
                    )
    return dict(p)

print con(map(float,[1,5,6,7])).get(21.0,0)