### 几段说明浮点数计算误差的程序

##### 加 0.1 重复 10 次
##x = 0.0
##n = 0
##while n < 10 :
##    x = x + 0.1
##    n = n + 1
##print(x, x == 1.0)


###### 希望循环体执行 100 次。实际做多少次？
##s = 0.0
##n = 0
##while s < 10.0 :
##    s = s + 0.1
##    n = n + 1
##print("Iterating", n , "times.","s =", s)


##from math import sqrt
##def triangle(a, b, c):
##    s = (a + b + c) / 2
##    area = sqrt(s * (s - a) * (s - b) * (s - c))
##    return area
##
##x = triangle(6, 8, 11)
##y = triangle(12, 17, 19) - triangle(4, 7, 9)
##z = triangle(3, 9, 7) * 4
##print("Area of a triangle:", x)
##print("Area of a triangle with a hole:", y)
##print("Volume of a triangle prism:", z)


### return 语句可以包括任意复杂的表达式
##from math import sqrt
##def triangle(a, b, c):
##    s = (a + b + c) / 2
##    return sqrt(s * (s - a) * (s - b) * (s - c))


### 检查参数的函数
##from math import sqrt
##def triangle(a, b, c):
##    if a > 0 and b > 0 and c > 0 and a+b > c and a+c > b and b+c > a :
##        s = (a + b + c) / 2
##        return sqrt(s * (s - a) * (s - b) * (s - c))
##    else:
##        return float("nan")


### 不返回值的函数
##from math import sqrt
##def printTriangle(a, b, c):
##    s = (a + b + c) / 2
##    area = sqrt(s * (s - a) * (s - b) * (s - c))
##    print("Area of triagnle:", area)
##
##printTriangle(6, 8, 11)
##printTriangle(4, 7, 9)
##printTriangle(12, 17, 19)


### 输出摄氏温度到华氏温度的转换表  
##def CtoF(begin, end, step) :
##    for x in range(begin, end, step) :
##        print(x, "->", x * 9 / 5 + 32)


### 计算阶乘的循环程序（包括函数定义）
##def fact(n) :
##    prod = 1
##    for k in range(2, n+1) :
##        prod = prod * k
##    return prod
##
##for i in range(4):
##    n = int(input("Next int:"))
##    print(fact(n))


### 递归定义的阶乘函数
##def fact(n):
##    if n == 0:
##        return 1
##    else:
##        return n * fact(n - 1)


### 求幂函数（尽可能减少乘法的次数，递归定义）
##def power(x, n):
##    if n == 0:
##        return 1
##    elif n == 1:
##        return x
##    elif n % 2 == 0:
##        return power(x*x, n//2)
##    else:
##        return power(x, n-1)*x
##
##print(power(2.0, 1))
##print(power(2.0, 5))
##print(power(2.0, 15))

 
### 求幂函数（尽可能减少乘法的次数）
##def power(x, n):
##    p = 1
##    while n > 0:
##        if n % 2 == 0:
##            x *= x
##            n //= 2
##        else:
##            p *= x
##            n -= 1
##    return p
##
##print(power(2.0, 1))
##print(power(2.0, 5))
##print(power(2.0, 15))

# maximum recursion depth < 1000


#### 语句/表达式不能跨越多行，出错的定义
##from math import sqrt
##def triangle(a, b, c) :
##    if a > 0 and b > 0 and c > 0 and a+b > c
##       and a+c > b and b+c > a:
##        s = (a + b + c) / 2
##        return sqrt(s * (s - a) * (s - b) * (s - c))
##    else:
##        return float("nan")


### 多行形式的语句/表达式（括号不匹配时自动延伸）
##from math import sqrt
##def triangle(a, b, c) :
##    if (a > 0 and b > 0 and c > 0 and a+b > c
##        and a+c > b and b+c > a) :
##        s = (a + b + c) / 2
##        return sqrt(s * (s - a) * (s - b) * (s - c))
##    else:
##        return float("nan")


### 多行形式的语句/表达式（使用续行符号 \ ）
##from math import sqrt
##def triangle(a, b, c) :
##    if a > 0 and b > 0 and c > 0 and a+b > c\
##       and a+c > b and b+c > a :
##        s = (a + b + c) / 2
##        return sqrt(s * (s - a) * (s - b) * (s - c))
##    else:
##        return float("nan")