#!/usr/bin/perl -w
use strict;
use Getopt::Std;
sub conv {
my ($val, $fac) = @_;
ref $fac ?
$fac->[0]->($val) :
$val * $fac;
}
sub reverse_conv {
my ($val, $fac) = @_;
ref $fac ?
$fac->[1]->($val) :
$val / $fac;
}
use constant SRC => 0;
use constant DST => 1;
use constant FAC => 2;
my @table = (
#### temperature
[ c => f => [
sub { ($_[0] * 9/5) + 32 },
sub { ($_[0] - 32) * 5/9 },
]],
[ c => k => [
sub { $_[0] + 273.16 },
sub { $_[0] - 273.16 },
]],
#### mass/weight
[ kg => g => 1000 ],
[ floz => g => 30 ],
[ lbs => kg => 0.4536 ],
#### distance
[ ft => m => 0.3048 ],
[ ft => in => 12 ],
[ in => cm => 2.54 ],
[ m => cm => 100 ],
[ yd => m => 0.9144 ],
[ km => m => 1000 ],
[ mile => km => 1.609347 ],
);
my @unit = sort keys %{{
map +($_->[SRC] => 1, $_->[DST] => 1), @table
}};
die << "END_USAGE" unless getopts('ap:', \my %opt) and @ARGV and (0 ==
+ @ARGV % 2);
usage: unitconv [-a] [-p precision] <val> <unit> [<val> <unit> [..]]
-p the number of decimal places [default: 2]
-a force all possible conversions to be shown, even if
insufficient display precision truncates the value to 0
<unit> can be one of: @unit
Results will be printed on one line per input val/unit pair.
END_USAGE
my $prec = $opt{p} || 2;
while(@ARGV) {
my (%val, $keys_before) = reverse splice @ARGV, 0, 2;
do {
$keys_before = keys %val;
for(@table) {
$val{$_->[DST]} = conv($val{$_->[SRC]}, $_->[FAC])
if exists $val{$_->[SRC]}
and not exists $val{$_->[DST]};
$val{$_->[SRC]} = reverse_conv($val{$_->[DST]}, $_->[FAC])
if exists $val{$_->[DST]}
and not exists $val{$_->[SRC]};
}
} until ($keys_before == keys %val);
unless($opt{a}) {
sprintf("%.*f", $prec, $val{$_}) == 0 and delete $val{$_}
for keys %val;
}
printf "% 8.${prec}f %s " x keys(%val) . "\n",
map +($val{$_} => $_), sort keys %val;
}
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