Tcl 嵌套循环|极客教程

Tcl 嵌套循环

Tcl允许在一个循环内使用另一个循环。下面的部分展示了一些示例来说明这个概念。

语法

Tcl语言中嵌套循环语句的语法如下：

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

嵌套的while循环语句的Tcl语言语法如下：

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

关于循环嵌套的最后注意事项是，你可以将任何类型的循环嵌套在任何其他类型的循环中。例如，一个for循环可以嵌套在一个while循环中，反之亦然。

示例

以下程序使用嵌套的for循环来找出从2到100的素数 –

#!/usr/bin/tclsh

set j 0;
for {set i 2} {i<100} {incr i} {
   for {set j 2} {j <= [expr i/j] } {incr j} {
      if {  [expr i%j] == 0 } {
         break
      } 
   }
   if {j >[expri/j] } {
      puts "i is prime"
   }
}

当上面的代码被编译和执行时，它产生以下结果 –

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