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alexm (4981)

alexm
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http://alexm.org/

Journal of alexm (4981)

Friday September 05, 2008
12:42 PM

Using up-to-date currency conversion rates

[ #37365 ]

A friend of mine is living this year in the USA, and she asked me how to program with Perl some unit conversions. The currency conversion is volatile since the ratio changes a lot, so I came up with this:

use strict;
use warnings;

use File::Basename;
use Cache::FileCache;
use Finance::Quote;

die "usage: $0 amount currency_from currency_to\n"
    unless @ARGV == 3;

my $amount = shift @ARGV;

my ($currency_from, $currency_to) = map { uc } @ARGV;

my ($filename) = fileparse($0, '.pl');

my $cache = Cache::FileCache->new({
    cache_root         => "$ENV{HOME}/.$filename",
    default_expires_in => '1 day',
});

my $quote = Finance::Quote->new();

my $ratio = $cache->get("$currency_from:$currency_to");

$ratio = $quote->currency($currency_from, $currency_to)
    unless defined $ratio;

die "sorry, cannot convert from $currency_from to $currency_to\n"
    unless defined $ratio;

$cache->set("$currency_from:$currency_to", $ratio);
print "$amount $currency_from = ", $amount * $ratio, " $currency_to\n";

She liked it, and so do I because it's so simple that it doesn't need comments at all. Just try:

$ perl exchange.pl 100 usd eur
100 USD = 70.22 EUR

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