D 编程 - 嵌套循环

D 编程语言允许在一个循环内嵌套另一个循环。以下部分将通过一些示例来说明这个概念。

语法

嵌套 for 循环 语法的格式如下：

for ( init; condition; increment ) {
   for ( init; condition; increment ) {
      statement(s);
   }
   statement(s);
}

嵌套 while 循环 语法的格式如下：

while(condition) {
   while(condition) {
      statement(s);
   }
   statement(s);
}

嵌套 do...while 循环 语法的格式如下：

do {
   statement(s);
   do {
      statement(s);
   }while( condition );

}while( condition );

关于循环嵌套的最后一点说明是，您可以将任何类型的循环放在任何其他类型的循环内。例如，for 循环可以放在 while 循环内，反之亦然。

示例

下面的程序使用嵌套 for 循环来查找 2 到 100 之间的素数：

import std.stdio;
 
int main () {
   /* local variable definition */
   int i, j;
   
   for(i = 2; i<100; i++) {
      for(j = 2; j <= (i/j); j++)
        if(!(i%j)) break; // if factor found, not prime
      if(j > (i/j)) writefln("%d is prime", i);
   }
 
   return 0;
}

编译并运行上述代码后，将产生以下结果：

2 is prime 
3 is prime 
5 is prime 
7 is prime
11 is prime 
13 is prime 
17 is prime 
19 is prime 
23 is prime 
29 is prime 
31 is prime 
37 is prime 
41 is prime 
43 is prime 
47 is prime 
53 is prime 
59 is prime 
61 is prime 
67 is prime 
71 is prime 
73 is prime 
79 is prime 
83 is prime 
89 is prime 
97 is prime