nested 循环

D编程语言允许在另一个循环中使用一个循环。 以下部分显示了几个用于说明该概念的示例。

语法 (Syntax)

nested for loop语句的语法如下 -

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

nested while loop语句的语法如下 -

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

nested do...while loop语句的语法如下 -

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

关于循环嵌套的最后一点是你可以将任何类型的循环放在任何其他类型的循环中。 例如，for循环可以在while循环内，反之亦然。

例子 (Example)

以下程序使用嵌套for循环来查找从2到100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;
}

编译并执行上述代码时，会产生以下结果 -

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