**Advent Calendar 2019**

### | **Day 20** | **Day 21** | **Day 22** |

The gift is presented by **Gustavo Chaves**. Today he is talking about his solutions to **Task #1: Base35 Representation** of **“The Weekly Challenge - 002”**.

#### Write a script that can convert numbers to and from a base35 representation, using the characters 0-9 and A-Y.

I cannot do it as a **one-liner** this time, but it was still fun. While trying to solve it I realized that it wouldn’t be much harder to implement a general solution to convert from any base to any base between **2** and **36**.

This is my solution:

```
#!/usr/bin/env perl
use 5.026;
use strict;
use integer;
use warnings;
my $usage = "Usage: $0 FROM_BASE TO_BASE NUMBER\n\nError";
die "$usage: invalid number of arguments\n"
unless @ARGV == 3;
my @digits = ('0' .. '9', 'A' .. 'Z');
my %digits = map {$digits[$_] => $_} 0 .. @digits-1;
my ($from_base, $to_base, $number) = @ARGV;
die "$usage: FROM_BASE must be between 2 and @digits\n"
if $from_base < 2 || $from_base > @digits;
die "$usage: TO_BASE must be between 2 and @digits\n"
if $to_base < 2 || $to_base > @digits;
sub from_base {
my ($base, $string) = @_;
my $n = 0;
$string =~ s/^0+//;
foreach my $char (reverse split //, $string) {
die "$usage: Invalid char in NUMBER: '$char'\n"
if $digits{$char} >= $base;
$n *= $base;
$n += $digits{$char};
}
return $n;
}
sub to_base {
my ($base, $n) = @_;
my $string = '';
for (my $i = $n; $i; $i /= $base) {
$string .= $digits[$i % $base];
}
return length $string ? reverse $string : '0';
}
say to_base($to_base, from_base($from_base, $number));
```

And this is how it works:

```
$ ./ch-1.pl 35 10 GUSTAVO
61183826754
$ ./ch-1.pl 10 35 61183826754
GUSTAVO
$ ./ch-1.pl 36 18 GUSTAVO
G674BB7G4
$ ./ch-1.pl 18 9 G674BB7G4
742882356461
$ ./ch-1.pl 9 3 742882356461
12112022222001210211021
$ ./ch-1.pl 3 2 12112022222001210211021
000100101011101100011101010110010011
$ ./ch-1.pl 2 36 000100101011101100011101010110010011
GUSTAVO
```

If you have any suggestion then please do share with us perlweeklychallenge@yahoo.com.