lambda 返回的是一個函數而不是一個結果
如果函數的返回值是一個函數 就可以實現f(a)(b)
下面是一個函數式編程的一個例子
#!/usr/bin/env python
# -*- coding:utf-8 -*-
__author__ = 'teng'
# f(a, b, c, d) = (a+b) * c -d
# f(a, b, c, d) = (a+b) * (c-d)
def calc2(s):
"""
def f_add(a, b): return a+b
def f_mul(a, b): return a*b
def f_sub(a, b): return a-b
:param s:
:return:
"""
if s == '+':
return lambda a, b: a+b
elif s== '*':
return lambda a, b: a*b
elif s=='-':
return lambda a,b:a-b
else:
assert False, "error: operator not defined"
# 返回一個函數
calc_dict={
'+':lambda a, b: a+b,
'*':lambda a, b: a*b,
'-':lambda a, b: a-b
}
if __name__=='__main__':
a, b, c, d = 1,2,3,4
print calc2('-')(calc2('*')(calc2('+')(a, b), c), d)
print calc2('*')(calc2('+')(a,b), calc2('-')(c,d))
operators = [(calc_dict['+'], [a, b]), (calc_dict['*'], [c]), (calc_dict['-'], [d])]
# 如果一個數字就直接操作 result和num2
for operator, num in operators:
if len(num)==1:
num1=result
num2=num[0]
else:
num1=num[0]
num2=num[1]
result=operator(num1, num2)
print result