Perlのテキスト解析変数が印刷に失敗する

Question

私は単位をインチに変換するはずのこのperlプログラムを持っています。しかし、ループ中に変数を出力することはありません。それはちょうど、標準は「に等しく、」印刷し、$ユニット2は、ここに私のコードここ

#!/usr/bin/perl 
#usage: perl convert.pl 

use Path::Class; 
use warnings; 
use autodie; # die if problem reading or writing a file 

my $dir = dir("./"); 

my $file = $dir->file("distances.txt"); 

# Read in the entire contents of a file 
my $content = $file->slurp(); 

# openr() returns an IO::File object to read from 
my $file_handle = $file->openr(); 

# Read in line at a time 
while(my $line = $file_handle->getline()) { 
    # parses string into value and unit 
    my ($val, $unit) = split /[\n]/, $line; 
    # initialize values 
    my ($val2, $unit2) = ""; 
    # check unit and apply corresponding math 
    if ($unit eq "in") { 
     $val2 = $val * 2.54; 
     $unit2 = "cm"; 
    } 
    else { 
     if ($unit eq "ft") { 
      $val2 = $val * 0.3048; 
      $unit2 = "m"; 
     } 
     else { 
      if ($unit eq "yd") { 
       $val2 = $val * 0.9144; 
       $unit2 = "m"; 
      } 
      else { 
       if ($unit eq "mi") { 
        $val2 = $val * 1.609347; 
        $unit2 = "km"; 
       }#close mile if statement 
      }#close else statement 
     }#close 2nd else statement 
    }#close 1st else statement 
    print $val, " ", $unit, " is equal to ", $val2, " ", $unit2, "\n"; 
} 

は、私が使用しているテキストファイルです

Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 1. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 2. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 3. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 4. 
is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 5. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 6. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 7. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 8. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 9. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 10. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 11. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 12. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 13. 
    is equal to 
Use of uninitialized value $unit2 in print at convert.pl line 47, <GEN1> line 14. 
    is equal to 

初期化されていないと述べています。

74 in 
10 in 
10 ft 
10 yd 
10 mi 
72 in 
6 ft 
2 yd 
300 ft 
100 yd 
158400 in 
13200 ft 
4400 yd 
2.5 mi 

Answer 1

while(my $line = $file_handle->getline()) { 
    # parses string into value and unit 
    my ($val, $unit) = split /[\n]/, $line; 

getline 1行を返します。それを改行[\n]で分割すると、行自体は$valになり、それ以外はunitになります。あなたはsplit ' 'に行きたがりますか？それをより読みやすくする理由単位変換のためのハッシュを使用して

は大幅にコードを短縮することがあります

my %units = (in => [ cm => 2.54 ], 
       ft => [ m => .3048 ], 
       yd => [ m => .9144 ], 
       mi => [ km => 1.609347 ], 
); 

while (my $line = $file_handle->getline) { 
    my ($val, $unit) = split ' ', $line; 
    my ($val2, $unit2) = ($units{$unit}[1] * $val, $units{$unit}[0]); 
    print "$val $unit is equal to $val2 $unit2\n"; 
}