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fixed RT #60782, corrected a miscalculation of auto precision #2

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fixed RT #60782, corrected a miscalculation of auto precision #2

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36 changes: 27 additions & 9 deletions lib/Geo/Hash.pm
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package Geo::Hash;

use warnings;
use strict;
use POSIX qw/ceil/;
use Carp;

=head1 NAME
Expand All @@ -16,6 +17,10 @@ This document describes Geo::Hash version 0.03

our $VERSION = '0.03';

use constant LOG2_OF_10 => log(10) / log(2);
use constant LOG2_OF_180 => log(180) / log(2);
use constant LOG2_OF_360 => log(360) / log(2);

=head1 SYNOPSIS

use Geo::Hash;
Expand Down Expand Up @@ -58,14 +63,25 @@ 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 >>
Expand All @@ -79,9 +95,11 @@ lat, lon pair.

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 $lat_bit = ceil( _num_of_decimal_places( $lat ) * LOG2_OF_10 + LOG2_OF_180 );
my $lon_bit = ceil( _num_of_decimal_places( $lon ) * LOG2_OF_10 + LOG2_OF_360 );
my $lat_len = _length_for_bits( $lat_bit, 1 );
my $lot_len = _length_for_bits( $lon_bit, 0 );
return $lat_len > $lot_len ? $lat_len : $lot_len;
}

=head2 C<< encode >>
Expand Down
17 changes: 17 additions & 0 deletions t/precision.t
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Original file line number Diff line number Diff line change
@@ -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;