Perl 嵌套循环
一个循环可以嵌套在另一个循环中。 Perl 允许嵌套所有类型的循环。
语法
Perl 中 嵌套循环 语句的语法如下 −
for ( init; condition; increment ) {
for ( init; condition; increment ) {
statement(s);
}
statement(s);
}
Perl 中 nested while 循环 语句的语法如下 −
while(condition) {
while(condition) {
statement(s);
}
statement(s);
}
Perl 中 nested do...while 循环 语句的语法如下 −
do{
statement(s);
do{
statement(s);
}while( condition );
}while( condition );
Perl 中 nested until loop 语句的语法如下 −
until(condition) {
until(condition) {
statement(s);
}
statement(s);
}
Perl 中 nested foreach 循环 语句的语法如下 −
foreach $a (@listA) {
foreach $b (@listB) {
statement(s);
}
statement(s);
}
示例
以下程序使用嵌套的 while 循环来显示用法 −
#/usr/local/bin/perl
$a = 0;
$b = 0;
# outer while loop
while($a < 3) {
$b = 0;
# inner while loop
while( $b < 3 ) {
print "value of a = $a, b = $b\n";
$b = $b + 1;
}
$a = $a + 1;
print "Value of a = $a\n\n";
}
这将产生以下结果 −
value of a = 0, b = 0 value of a = 0, b = 1 value of a = 0, b = 2 Value of a = 1 value of a = 1, b = 0 value of a = 1, b = 1 value of a = 1, b = 2 Value of a = 2 value of a = 2, b = 0 value of a = 2, b = 1 value of a = 2, b = 2 Value of a = 3
