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我正在尝试运行这个 Perl 程序。

#!/usr/bin/perl
# ---------------     exchange.pl     -----------------

&read_exchange_rate;     # read exchange rate into memory

# now let's cycle, asking the user for input...

print "Please enter the amount, appending the first letter of the name of\n";
print "the currency that you're using (franc, yen, deutschmark, pound) -\n";
print "the default value is US dollars.\n\n";
print "Amount: ";

while (<STDIN>) {

  ($amnt,$curr) = &breakdown(chop($_));

  $baseval = $amnt * (1/$rateof{$curr});

  printf("%2.2f USD, ", $baseval * $rateof{'U'});
  printf("%2.2f Franc, ", $baseval * $rateof{'F'});
  printf("%2.2f DM, ", $baseval * $rateof{'D'});
  printf("%2.2f Yen, and ", $baseval * $rateof{'Y'});
  printf("%2.2f Pound\n\nAmount: ", $baseval * $rateof{'P'});
}

sub breakdown {
   @line = split(" ", $_);

   $amnt = $line[0];
   if ($#line == 1) {
     $curr = $line[1];
     $curr =~ tr/a-z/A-Z/;         # uppercase
     $curr = substr($curr, 0, 1);  # first char only
   } else { $curr = "U"; }
   return ($amnt, $curr);
}

sub read_exchange_rate {
  open(EXCHRATES, "

每当它到达第 17 行 ( $baseval = $amnt * (1/$rateof{$curr})) 时，我都会收到错误消息Illegal division by zero。

怎么了？

我是 Perl 的新手，所以请解释一下你的答案。

这只发生在 Strawberry Perl 中。ActivePerl 可以工作，但它会将所有货币转换列为 0.0。

更新：我将代码更改为如下所示：

#!/usr/bin/perl

&read_exchange_rate;     # read exchange rate into memory

# now let's cycle, asking the user for input...

print "Please enter the amount, appending the first letter of the name of\n";
print "the currency that you're using (franc, yen, deutschmark, pound) -\n";
print "the default value is US dollars.\n\n";
print "Amount: ";

while (<STDIN>) {

  ($amnt,$curr) = &breakdown(chomp($_));

  $baseval = eval { $amnt * (1/$rateof{$curr}) };

  printf("%2.2f USD, ", $baseval * $rateof{'U'});
  printf("%2.2f Franc, ", $baseval * $rateof{'F'});
  printf("%2.2f DM, ", $baseval * $rateof{'D'});
  printf("%2.2f Yen, and ", $baseval * $rateof{'Y'});
  printf("%2.2f Pound\n\nAmount: ", $baseval * $rateof{'P'});
}

sub breakdown {
   @line = split(" ", $_);

   $amnt = $line[0];
   if ($#line == 1) {
     $curr = $line[1];
     $curr =~ tr/a-z/A-Z/;         # uppercase
     $curr = substr($curr, 0, 1);  # first char only
   } else { $curr = "U"; }
   return ($amnt, $curr);
}

sub read_exchange_rate {
  open EXCHRATES, "<exchange.db" or die "$!\n";

  while ( <EXCHRATES> ) {
    chomp; split;
    $curr = $_[0];
    $val  = $_[1];
    $rateof{$curr} = $val;
  }
  close(EXCHRATES);
}

现在，当我使用 Open With（是的，我在 Windows 上）时，我在 Strawberry Perl 中得到了这个： No such file or directory 但如果我双击它，它开始正常，但会话看起来像这样：

Please enter the amount, appending the first letter of the name of
the currency that you're using (franc, yen, deutschmark, pound) -
the default value is US dollars.

Amount: 5 y
0.00 USD, 0.00 Franc, 0.00 DM, 0.00 Yen, and 0.00 Pound

Amount:

显然有些不对劲。chop我已经更改了to的所有实例chomp。现在我该怎么做？

4

1 回答 1

6

您的代码不起作用的原因是chop返回从字符串末尾删除的字符，而不是删除最后一个字符的字符串。您还应该使用chompwhich 是相同的，只是它仅在它是换行符时才返回最后一个字符。当文件的最后一行没有以换行符终止时，这可以避免出现问题。

此外，您必须始终use strict使用and启动 Perl 程序，use warnings并在第一次使用时声明所有变量。

您还应该避免使用&名称中的 & 号调用子例程。自 Perl 4 以来——大约 20 年前，这一直不是正确的做法。你的电话应该看起来像

read_exchange_rate();
于 2013-03-07T15:31:26.150 回答