regex - 在串联(.)或字符串中使用未初始化的值-Perl问题

Question

我是第一次发布此信息。我在论坛中经历了类似的问题，但仍然无法确定为什么会收到此错误。

这是我要制作的示例代码。

use strict;
use warnings;
my ($m, $b) = @ARGV;
my $count_args = $#ARGV + 1;
my $times = 2**$m;
main();

sub main {
     if ( $m =~ /^\d+$/ ) {
         if ( $b =~ /^and$/i ) {
             func_and();    
         }   else {
             print " not supported\n";
         }
     }   else {
         print " enter valid number of pins\n";
     }
}
sub func_and {
    my $bit;
    for ( my $i = 0 ; $i < $times ; $i++ ) {
        my $p = sprintf( "%0${m}b", $i );    
        print "$p\t";
        my @c = split( '', $p );             
        my $result = 3;                      
        foreach  $bit (@c) {
            if ( $result < 3 ) {
                $result = $result && $bit;    
            } else {
                $result = $bit;    
            }
        }
        print "result for AND operation on $bit is $result \n";
    }
}

如果我将输入作为 perl AND.pl 2 and
我得到的错误是 Use of uninitialized value in concatenation (.) or string at NAND.pl line 34。
还有其他方法来声明$位变量吗？以及如何初始化呢？
谢谢

Answer 1

更改:

print "result for AND operation on $bit is $result \n";

至:

print "result for AND operation on $p is $result \n";

然后，您可以将 $bit本地化为 foreach循环:

foreach my $bit (@c) {

perldoc perlsyn:

The foreach loop iterates over a normal list value and sets the variable VAR to be each element of the list in turn. If the variable is preceded with the keyword my, then it is lexically scoped, and is therefore visible only within the loop. Otherwise, the variable is implicitly local to the loop and regains its former value upon exiting the loop. If the variable was previously declared with my, it uses that variable instead of the global one, but it's still localized to the loop.

$bit在循环之前未初始化，因此在循环之后仍保持不变。