“全局符号需要显式包名"的解释 [英] Explanation of 'global symbol requires explicit package name'
问题描述
我一直在学习 Perl,每当我编写一个重要的脚本时,我总是收到此错误消息.我一直认为我对它有很好的理解,但我想我没有.这是一个带有以下错误的草率马尔可夫链示例(未经测试).
I've been learning Perl and whenever I write a non-trivial script I always get this error message. I always think I have a good understanding of it, but I suppose I don't. Here is a sloppy markov chain example (not tested) with the errors below.
#!/usr/bin/perl -w
use strict;
sub croak { die "$0: @_: $!\n"; }
sub output {
my %chains = shift;
my @keys = keys %chains;
my $index = rand($keys);
my $key = $keys[$index];
my $out_buf = $key;
for (my $i = 0; $i < 100; ++$i) {
my $aref = $chains{$key};
my $word = @$aref[rand($aref)];
$out_buf .= " $word";
$key =~ s/.+ //;
$key .= " $word";
}
print $out_buf, "\n";
}
sub get_chains {
my %chains;
my @prefixes
while (my $line = <FILE>) {
my @words = split " ", $line;
foreach my $word (@words) {
if ($prefixes == 2) {
my $key = join " ", @prefixes;
my $arr_ref = $chains{$key};
push(@$arr_ref, $word);
shift @prefixes;
}
push(@prefixes, $word);
}
}
return %chains;
}
sub load_book {
my $path_name = shift @ARGV;
open(FILE, $path_name) || croak "File not found.\n";
}
load_book;
my %chains = get_chains;
output %chains;
----ERRORS----
"my" variable $line masks earlier declaration in same statement at markov.pl line 33.
"my" variable $path_name masks earlier declaration in same scope at markov.pl line 55.
Global symbol "$keys" requires explicit package name at markov.pl line 12.
syntax error at markov.pl line 32, near ") {"
Global symbol "$prefixes" requires explicit package name at markov.pl line 36.
Global symbol "%chains" requires explicit package name at markov.pl line 48.
syntax error at markov.pl line 49, near "}"
syntax error at markov.pl line 56, near "}"
Execution of markov.pl aborted due to compilation errors.
我犯了什么错误?
推荐答案
您的脚本中存在三个语法错误:
There are three syntax errors in your script:
全局符号$keys"需要在 markov.pl 第 12 行明确的包名称.
您没有声明 $keys,并且由于使用严格",这是一个致命错误.你可能的意思是:
You didn't declare $keys, and because of "use strict", that is a fatal error. You probably meant:
my $index = rand(@keys);
第二个错误:
全局符号$prefixes"需要在 markov.pl 第 36 行显式包名称.
是同一件事:你的意思是:
is the same thing: you meant:
if (@prefixes == 2) {
最后,在第 30 行,后面缺少一个分号:
Finally, in line 30, you're missing a semicolon after:
my @prefixes
这会混淆解析器,并导致所有其他错误和警告.
This confuses the parser, and causes all the other errors and warnings.
如果您不清楚 sigils 的使用,您可能需要阅读 perldata 文档($, @, %).
You may want to read the perldata documentation if you're unclear about the use of sigils ($, @, %).
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