# D語言關係運算子

== 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

```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;
}```

```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```