D語言關係運算子 - tw511教學網

下表列出了所有D語言支援的關係運算子。假設變數A=10和變數B=20，則：

運算子	描述	範例
==	檢查，如果兩個運算元的值相等與否，如果是則條件為真。	(A == B) is not true.
!=	檢查，如果兩個運算元的值相等與否，如果值不相等，則條件變為真。	(A != B) is true.
>	如果左運算元的值大於右運算元的值，如果是則條件為真檢查。	(A > B) is not true.
<	如果檢查左運算元的值小於右運算元的值，如果是則條件為真。	(A < B) is true.
>=	如果左運算元的值大於或等於右運算元的值，如果是則條件為真檢查。	(A >= B) is not true.
<=	如果檢查左運算元的值小於或等於右運算元的值，如果是則條件為真。	(A <= B) is true.

範例

試試下面的例子就明白了所有的D程式設計語言的關係運算子：

import std.stdio;

int main(string[] args)
{
  int a = 21;
   int b = 10;
   int c ;

   if( a == b )
   {
      writefln("Line 1 - a is equal to b
" );
   }
   else
   {
      writefln("Line 1 - a is not equal to b
" );
   }
   if ( a < b )
   {
      writefln("Line 2 - a is less than b
" );
   }
   else
   {
      writefln("Line 2 - a is not less than b
" );
   }
   if ( a > b )
   {
      printf("Line 3 - a is greater than b
" );
   }
   else
   {
      writefln("Line 3 - a is not greater than b
" );
   }
   /* Lets change value of a and b */
   a = 5;
   b = 20;
   if ( a <= b )
   {
      printf("Line 4 - a is either less than or equal to  b
" );
   }
   if ( b >= a )
   {
      writefln("Line 5 - b is either greater than  or equal to b
" );
   }
   return 0;
}

當編譯並執行上面的程式它會產生以下結果：

Line 1 - a is not equal to b

Line 2 - a is not less than b

Line 3 - a is greater than b

Line 4 - a is either less than or equal to  b

Line 5 - b is either greater than  or equal to b