Skip Menu |
 

This queue is for tickets about the Geo-Hash CPAN distribution.

Report information
The Basics
Id: 60782
Status: new
Priority: 0/
Queue: Geo-Hash

People
Owner: Nobody in particular
Requestors: hiratara [...] cpan.org
Cc:
AdminCc:

Bug Information
Severity: Wishlist
Broken in: 0.02
Fixed in: (no value)



Subject: corrected a miscalculation of auto precision
MIME-Version: 1.0
X-Mailer: MIME-tools 5.427 (Entity 5.427)
X-RT-Original-Encoding: utf-8
Content-Type: multipart/mixed; boundary="----------=_1282889190-11057-168"
Content-Length: 0
Content-Type: text/plain; charset="UTF-8"
Content-Disposition: inline
Content-Transfer-Encoding: binary
Content-Length: 248
Download (untitled) / with headers
text/plain 248b
Hi. It seems that there are some errors in auto precision calculation, especially in how to handle integers. I tried to fix it. Check out the patch attached or see following github branch. http://github.com/hiratara/Geo-Hash/tree/fix-precision
Subject: fix-precision.patch
MIME-Version: 1.0
Content-Type: application/octet-stream; name="fix-precision.patch"
X-Mailer: MIME-tools 5.427 (Entity 5.427)
Content-Disposition: inline; filename="fix-precision.patch"
Content-Transfer-Encoding: base64
Content-Length: 2246
Download fix-precision.patch
text/x-diff 2.1k
diff --git a/lib/Geo/Hash.pm b/lib/Geo/Hash.pm index 5093df7..1604edf 100644 --- a/lib/Geo/Hash.pm +++ b/lib/Geo/Hash.pm @@ -2,6 +2,7 @@ package Geo::Hash; use warnings; use strict; +use POSIX qw/ceil/; use Carp; =head1 NAME @@ -58,14 +59,23 @@ sub _mid { return ( $ar->[$wh][0] + $ar->[$wh][1] ) / 2; } -# The number of bits necessary to represent the specified number of -# decimal digits -sub _d2b { int( shift() * 3.32192809488736 + 1 ) } - -sub _bits_for_number { +sub _num_of_decimal_places($) { my $n = shift; return 0 unless $n =~ s/.*\.//; - return _d2b( length $n ); + return length $n; +} + +sub _length_for_bits($$) { + my ($bits, $is_lat) = @_; + my $q = int($bits / 5); + my $r = $bits % 5; + if ($r == 0) { + return $q * 2; + } elsif ($r <= ($is_lat ? 2 : 3)) { + return $q * 2 + 1; + } else { + return $q * 2 + 2; + } } =head2 C<< precision >> @@ -77,11 +87,16 @@ lat, lon pair. =cut +use constant LOG2_10 => log(10) / log(2); +use constant LOG2_180 => log(180) / log(2); +use constant LOG2_360 => log(360) / log(2); sub precision { my ( $self, $lat, $lon ) = @_; - my $lab = _bits_for_number( $lat ) + 8; - my $lob = _bits_for_number( $lon ) + 9; - return int( ( ( $lab > $lob ? $lab : $lob ) + 1 ) / 2.5 ); + my $lab = ceil(_num_of_decimal_places($lat) * LOG2_10 + LOG2_180); + my $lob = ceil(_num_of_decimal_places($lon) * LOG2_10 + LOG2_360); + my $la_len = _length_for_bits($lab, 1); + my $lo_len = _length_for_bits($lob, 0); + return $la_len > $lo_len ? $la_len : $lo_len; } =head2 C<< encode >> diff --git a/t/precision.t b/t/precision.t new file mode 100644 index 0000000..15cac8c --- /dev/null +++ b/t/precision.t @@ -0,0 +1,17 @@ +use strict; +use warnings; +use Test::More; +use Geo::Hash; + +my $gh = Geo::Hash->new; +is $gh->precision('45', '-120'), 4; +is $gh->precision('45.0', '-120'), 5; +is $gh->precision('45', '-120.0'), 5; +is $gh->precision('45.00', '-120'), 6; +is $gh->precision('45', '-120.00'), 7; +is $gh->precision('45.000', '-120'), 8; +is $gh->precision('45', '-120.000'), 8; +is $gh->precision('45.00000', '-120'), 10; +is $gh->precision('45', '-120.00000'), 11; + +done_testing;


This service is sponsored and maintained by Best Practical Solutions and runs on Perl.org infrastructure.

Please report any issues with rt.cpan.org to rt-cpan-admin@bestpractical.com.