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简介

C++ Reference¹提供了C++标准库的详细文档和参考信息.

Arithmetic operators

算数操作很多,这里只针对除零问题进行简单分析.关于其它一些数学计算如atan2³也有关于输入时inf或者NaN的标准定义

Multiplicative operators

主要包括乘法(Multiplication),除法(division)和取余(remainder)

• lhs * rhs
• lhs / rhs
• lhs % rhs

Division

• c++整数相除，除数=0，标准未定义，由编译器决定，通常是程序崩溃（win，qnx）
• c++浮点数相除（只要有1个操作数被定义为浮点数，如float，double，另一个操作数即使整数也会隐式转换为浮点数），被除数=0，程序不崩溃。
  • 任意操作数NaN，返回NaN（not a number）
  • 带符号无穷大，+/0.0==inf，-/0.0=-inf
  • 0.0/0.0=NaN

参考C++ Arithmetic operators²中除法定义

In the remaining description in this section, “operand(s)>”, lhs and rhs refer to the converted operand(s).

2) The result of built-in division is lhs divided by rhs. >If rhs is zero, the behavior is undefined.
If both operands have an integral type, the result is the >algebraic quotient (performs integer division): the >quotient is truncated towards zero (fractional part is >discarded).
If both operands have a floating-point type, and the type >supports IEEE floating-point arithmetic (see >std::numeric_limits::is_iec559):

• If one operand is NaN, the result is NaN.
• Dividing a non-zero number by ±0.0 gives the >correctly-signed infinity and FE_DIVBYZERO is raised.
• Dividing 0.0 by 0.0 gives NaN and FE_INVALID is raised.

input

int ia0 = 0;
int ia1 = 1;
double db0 = 0.0;
double db1 = 1.0;
double db2 = -1.0;

std::cout << "1.0/0= " << db1/ia0 << std::endl;
std::cout << "-1.0/0= " << db2/ia0 << std::endl;
std::cout << "1.0/0.0= " << db1/db0 << std::endl;
std::cout << "-1.0/0.0= " << db2/db0 << std::endl;
std::cout << "1/0= " << ia1/ia0 << std::endl;

output

1.0/0= inf
-1.0/0= -inf
1.0/0.0= inf
-1.0/0.0= -inf
unknown file: error: SEH exception with code 0xc0000094 thrown in the test body.

¹. https://en.cppreference.com/w/ ↩

². https://en.cppreference.com/w/cpp/language/operator_arithmetic ↩

³. https://en.cppreference.com/w/cpp/numeric/math/atan2 ↩

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