[討論] int vs enum

[ric2k1 (Ric)]

雖然說 enum type 是表示 a set of constant integers,

enum 與 int 還是不能隨便轉換 ---

======

enum E { A, B };

int main()
{
   E e;
   e = 1;
   int i = 2;
   e = i;

   int j = e;
}


======

cp44.cpp:6: error: invalid conversion from `int' to `E'
cp44.cpp:8: error: invalid conversion from `int' to `E'


所以說 conversion from enum to int 是可以的, e.g. int j = e;

但是 conversion from int to enum 就是 compiler error.

原因很簡單,

因為 enum 只是定義 subset of int.

conversing int to enum may produce illegal enum value.

而反之 (enum to int) 就不會有問題.

--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 59.121.132.121