Data commit

Task/Negative-base-numbers/Perl/negative-base-numbers.pl

@@ -0,0 +1,37 @@
+use strict;
+use feature 'say';
+use POSIX qw(floor);
+use ntheory qw/fromdigits todigits/;
+
+sub encode {
+    my($n, $b) = @_;
+    my @out;
+    my $r = 0;
+
+    while ($n) {
+        $r = $n % $b;
+        $n = floor $n/$b;
+        $n += 1, $r -= $b if $r < 0;
+        push @out, todigits($r, -$b) || 0;
+    }
+    join '', reverse @out;
+}
+
+sub decode {
+    my($s, $b) = @_;
+    my $total = 0;
+    my $i = 0;
+    for my $c (reverse split '', $s) {
+        $total += (fromdigits($c, -$b) * $b**$i);
+        $i++;
+    }
+    $total
+}
+
+say ' 10 in base  -2: ', encode(10, -2);
+say ' 15 in base -10: ', encode(15, -10);
+say '146 in base  -3: ', encode(146, -3);
+say '';
+say  '11110 from base  -2: ', decode("11110", -2);
+say  '21102 from base  -3: ', decode("21102", -3);
+say  '  195 from base -10: ', decode("195",  -10);