Perl 循环嵌套
Perl 教程
· 2019-02-26 22:28:21
Perl 语言允许在一个循环内使用另一个循环，下面演示几个实例来说明这个概念。
语法
嵌套 for 循环语句的语法：
for ( init; condition; increment ){
for ( init; condition; increment ){
statement(s);
}
statement(s);
}
嵌套 while 循环语句的语法：
while(condition){
while(condition){
statement(s);
}
statement(s);
}
嵌套 do...while 循环语句的语法：
do{
statement(s);
do{
statement(s);
}while( condition );
}while( condition );
嵌套 until 循环语句的语法：
until(condition){
until(condition){
statement(s);
}
statement(s);
}
嵌套 foreach 循环语句的语法：
foreach $a (@listA){
foreach $b (@listB){
statement(s);
}
statement(s);
}
实例
#!/usr/bin/perl
$a = 0;
$b = 0;
# 外部循环
while($a < 3){
$b = 0;
# 内部循环
while( $b < 3 ){
print "a = $a, b = $b\n";
$b = $b + 1;
}
$a = $a + 1;
print "a = $a\n\n";
}
执行以上程序，输出结果为：
a = 0, b = 0 a = 0, b = 1 a = 0, b = 2 a = 1 a = 1, b = 0 a = 1, b = 1 a = 1, b = 2 a = 2 a = 2, b = 0 a = 2, b = 1 a = 2, b = 2 a = 3
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