下表列出了所有D语言支持的关系运算符。假设变量A=10和变量B=20，则：
| 运算符 | 描述 | 示例 |
|---|---|---|
| == | 检查，如果两个操作数的值相等与否，如果是则条件为真。 | (A == B) is not true. |
| != | 检查，如果两个操作数的值相等与否，如果值不相等，则条件变为真。 | (A != B) is true. |
| > | 如果左操作数的值大于右操作数的值，如果是则条件为真检查。 | (A > B) is not true. |
| < | 如果检查左操作数的值小于右操作数的值，如果是则条件为真。 | (A < B) is true. |
| >= | 如果左操作数的值大于或等于右操作数的值，如果是则条件为真检查。 | (A >= B) is not true. |
| <= | 如果检查左操作数的值小于或等于右操作数的值，如果是则条件为真。 | (A <= B) is true. |
试试下面的例子就明白了所有的D编程语言的关系运算符：
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;
}
当编译并执行上面的程序它会产生以下结果：
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
