c - 如果/或 % 运算符的一个或两个操作数是负数，结果是否将由实现定义？

Question

例如这些表达式的值是什么？它们依赖于编译器吗？

-7/3   -7%3
7/-3   7%-3
-7/-3  -7%-3

Answer 1

在 C89 中，除法 / 的结果可以被截断为负操作数。

在 C99 或更高版本中，结果将被截断为零。

% 运算符取决于所有标准中 / 的行为。

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引用资料:

C89 § 3.3.5

If either operand is negative, whether the result of the / operator is the largest integer less than or equal to the algebraic quotient or the smallest integer greater than or equal to the algebraic quotient is implementation-defined, as is the sign of the result of the % operator. If the quotient a/b is representable. the expression (a/b) * b + a%b shall equal a.

和

C11 § 6.5.5

When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded

带脚注:

This is often called "truncation toward zero"