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Perl 循环嵌套

Perl 循环 Perl 循环

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

Perl 循环 Perl 循环