Geohash: Difference between revisions
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{{draft task}}
Geohashes are used to represent standard latitude and longitude coordinates as single values in the form of a simple string -- using the digits (0-9) and the letters (B-Z excluding I, L, O). They can vary in length, with more characters in the string representing more precision.
;
Generate a Geohash with a desired precision from a coordinate represented as an array of two
Line 17 ⟶ 18:
From the Wikipedia page, geohashes can be "useful in database systems where queries on a single index are much easier or faster than multiple-index queries."
;Extra credit
Provide a decode function to convert a geohash code back to latitude and longitude, expressed either as ranges or in median +/- deviation format.
;Reference
* [[wp:Geohash|Wikipedia article - Geohash]].
=={{header|11l}}==
{{trans|Python}}
<syntaxhighlight lang="11l">V ch32 = Array(‘0123456789bcdefghjkmnpqrstuvwxyz’)
V bool2ch = Dict(enumerate(ch32), (i, ch) -> (bin(i).zfill(5), ch))
V ch2bool = Dict(bool2ch.items(), (k, v) -> (v, k))
F bisect(val, =mn, =mx, =bits)
V mid = (mn + mx) / 2
I val < mid
bits <<= 1
mx = mid
E
bits = bits << 1 [|] 1
mn = mid
R (mn, mx, bits)
F encoder(lat, lng, pre)
V (latmin, latmax) = (-90.0, 90.0)
V (lngmin, lngmax) = (-180.0, 180.0)
V bits = Int64(0)
L(i) 0 .< pre * 5
I i % 2 != 0
(latmin, latmax, bits) = bisect(lat, latmin, latmax, bits)
E
(lngmin, lngmax, bits) = bisect(lng, lngmin, lngmax, bits)
V b = bin(bits).zfill(pre * 5)
V geo = ((0 .< pre).map(i -> :bool2ch[@b[i * 5 .< (i + 1) * 5]]))
R geo.join(‘’)
F decoder(geo)
V (minmaxes, latlong) = ([[-90.0, 90.0], [-180.0, 180.0]], 1B)
L(c) geo
L(bit) :ch2bool[c]
minmaxes[latlong][bit != ‘1’] = sum(minmaxes[latlong]) / 2
latlong = !latlong
R minmaxes
L(lat, lng, pre) [(51.433718, -0.214126, 2),
(51.433718, -0.214126, 9),
(57.64911, 10.40744, 11)]
print(‘encoder(lat=#.6, lng=#.6, pre=#.) = '#.'’.format(lat, lng, pre, encoder(lat, lng, pre)))</syntaxhighlight>
{{out}}
<pre>
encoder(lat=51.433718, lng=-0.214126, pre=2) = 'gc'
encoder(lat=51.433718, lng=-0.214126, pre=9) = 'gcpue5hp4'
encoder(lat=57.649110, lng=10.407440, pre=11) = 'u4pruydqqvj'
</pre>
=={{header|Action!}}==
{{libheader|Action! Tool Kit}}
{{libheader|Action! Real Math}}
<syntaxhighlight lang="action!">INCLUDE "H6:REALMATH.ACT"
CHAR ARRAY code32="0123456789bcdefghjkmnpqrstuvwxyz"
PROC Encode(REAL POINTER lat,lng BYTE prec CHAR ARRAY hash)
REAL latMin,latMax,lngMin,lngMax,mid,r2,sum
REAL POINTER v,min,max
BYTE even,hashV,bits
IntToReal(2,r2)
ValR("-90",latMin) ValR("90",latMax)
ValR("-180",lngMin) ValR("180",lngMax)
hash(0)=0 hashV=0 even=1 bits=0
WHILE hash(0)<prec
DO
IF even THEN
v=lng min=lngMin max=lngMax
ELSE
v=lat min=latMin max=latMax
FI
RealAdd(min,max,sum)
RealDiv(sum,r2,mid)
hashV==LSH 1
IF RealGreaterOrEqual(v,mid) THEN
hashV==+1
RealAssign(mid,min)
ELSE
RealAssign(mid,max)
FI
even=1-even
IF bits<4 THEN
bits==+1
ELSE
bits=0
hash(0)==+1
hash(hash(0))=code32(hashV+1)
hashV=0
FI
OD
RETURN
BYTE FUNC GetCodeVal(CHAR c)
BYTE i
FOR i=1 TO code32(0)
DO
IF c=code32(i) THEN
RETURN (i-1)
FI
OD
RETURN (0)
PROC Decode(CHAR ARRAY hash REAL POINTER lat,lng,latPrec,lngPrec)
REAL latMin,latMax,lngMin,lngMax,r2,sum
REAL POINTER min,max
BYTE i,j,v,mask,even
IntToReal(2,r2)
ValR("-90",latMin) ValR("90",latMax)
ValR("-180",lngMin) ValR("180",lngMax)
even=1
FOR i=1 TO hash(0)
DO
v=GetCodeVal(hash(i))
mask=16
FOR j=1 TO 5
DO
IF even THEN
min=lngMin
max=lngMax
ELSE
min=latMin
max=latMax
FI
RealAdd(min,max,sum)
IF (v&mask)=mask THEN
RealDiv(sum,r2,min)
ELSE
RealDiv(sum,r2,max)
FI
even=1-even
mask==RSH 1
OD
OD
RealAdd(latMin,latMax,sum)
RealDiv(sum,r2,lat)
RealSub(latMax,lat,latPrec)
RealAdd(lngMin,lngMax,sum)
RealDiv(sum,r2,lng)
RealSub(lngMax,lng,lngPrec)
RETURN
PROC Test(CHAR ARRAY latStr,lngStr BYTE prec)
CHAR ARRAY hash(255)
REAL lat,lng,resLat,resLng,latPrec,lngPrec
ValR(latStr,lat) ValR(lngStr,lng)
Encode(lat,lng,prec,hash)
Decode(hash,resLat,resLng,latPrec,lngPrec)
Print("Input: ") PrintR(lat) Print(", ")
PrintR(lng) PrintF(", prec=%B%E",prec)
PrintF("Encode: %S%E",hash)
Print("Decode: ") PrintR(resLat) Print(" (+/-") PrintR(latPrec)
Print("), ") PrintR(resLng) Print(" (+/-") PrintR(lngPrec)
PrintE(")") PutE()
RETURN
PROC Main()
Put(125) PutE() ;clear the screen
Test("51.433718","-0.214126",2)
Test("51.433718","-0.214126",9)
Test("57.64911","10.40744",11)
RETURN</syntaxhighlight>
{{out}}
[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Geohash.png Screenshot from Atari 8-bit computer]
<pre>
Input: 51.433718, -0.214126, prec=2
Encode: gc
Decode: 53.4375 (+/-2.8125), -5.625 (+/-5.625)
Input: 51.433718, -0.214126, prec=9
Encode: gcpue5hp4
Decode: 51.433717 (+/-2.15E-05), -0.21412611 (+/-2.14577E-05)
Input: 57.64911, 10.40744, prec=11
Encode: u4pruydqqvm
Decode: 57.64911 (+/-1E-06), 10.40743967 (+/-6.7E-07)
</pre>
=={{header|Factor}}==
Factor comes with the <code>geohash</code> vocabulary. See the implementation [https://docs.factorcode.org/content/vocab-geohash.html here].
{{works with|Factor|0.99 2020-03-02}}
<syntaxhighlight lang="factor">USING: formatting generalizations geohash io kernel sequences ;
: encode-geohash ( latitude longitude precision -- str )
[ >geohash ] [ head ] bi* ;
! Encoding
51.433718 -0.214126 2
51.433718 -0.214126 9
57.649110 10.407440 11
[
3dup encode-geohash
"geohash for [%f, %f], precision %2d = %s\n" printf
] 3 3 mnapply nl
! Decoding
"u4pruydqqvj" dup geohash>
"coordinates for %s ~= [%f, %f]\n" printf</syntaxhighlight>
{{out}}
<pre>
geohash for [51.433718, -0.214126], precision 2 = gc
geohash for [51.433718, -0.214126], precision 9 = gcpue5hp4
geohash for [57.649110, 10.407440], precision 11 = u4pruydqqvj
coordinates for u4pruydqqvj ~= [57.649110, 10.407439]
</pre>
=={{header|F_Sharp|F#}}==
<syntaxhighlight lang="fsharp">
// Create a geoHash String. Nigel Galloway: June 26th., 2020
let fG n g=Seq.unfold(fun(α,β)->let τ=(α+β)/2.0 in Some(if τ>g then (0,(α,τ)) else (1,(τ,b)))) n
let fLat, fLon = fG (-90.0,90.0), fG (-180.0,180.0)
let fN n g z=Seq.zip(fLat n)(fLon g)|>Seq.collect(fun(n,g)->seq{yield g;yield n})|>Seq.take(z*5)|>Seq.splitInto z
let fI=Array.fold2 (fun Σ α β->Σ+α*β) 0 [|16; 8; 4; 2; 1|]
let geoHash n g z=let N="0123456789bcdefghjkmnpqrstuvwxyz" in [|for τ in fN n g z do yield N.[fI τ]|] |> System.String
printfn "%s\n%s\n%s" (geoHash 51.433718 -0.214126 2) (geoHash 51.433718 -0.214126 9) (geoHash 57.64911 10.40744 11)
</syntaxhighlight>
{{out}}
<pre>
gc
gcpue5hp4
u4pruydqqvj
</pre>
=={{header|Go}}==
{{trans|Swift}}
<
import (
Line 89 ⟶ 336:
fmt.Printf("geohash for %v, precision %-2d = %s\n", loc, precs[i], geohash)
}
}</
{{out}}
Line 98 ⟶ 345:
</pre>
=={{header|J}}==
<syntaxhighlight lang=J>gdigits=: '0123456789bcdefghjkmnpqrstuvwxyz'
geohash=: {{
bits=. 3*x
x{.gdigits{~_5 #.\,|:|.(bits#2)#:<.(2^bits)*(y+90 180)%180 360
}}</syntaxhighlight>
Note that the test cases suggest that rounding should never be used when generating a geohash. This guarantees that a short geohash is always a prefix of a longer geohash for the same location.
<syntaxhighlight lang=J> 2 geohash 51.433718 _0.214126
gc
9 geohash 51.433718 _0.214126
gcpue5hp4
11 geohash 57.64911 10.40744
u4pruydqqvj</syntaxhighlight>
And, going the other direction (producing a min and max lat and long value for the geohash):
<syntaxhighlight lang=J>hsahoeg=: {{
bits=: |.|:0,~_2]\,(5#2)#:gdigits i.y
scale=: %2^{:$bits
lo=: scale*#.bits
hi=: scale*(2^1+1 0*2|#y)+#.bits
0.5*_180+360*lo,.hi
}}</syntaxhighlight>
This gives us:
<syntaxhighlight lang=J> hsahoeg 'gc'
50.625 56.25
_5.625 0
hsahoeg 'gcpue5hp4'
51.4337 51.4337
_0.107074 _0.107052
hsahoeg 'u4pruydqqvj'
57.6491 57.6491
5.20372 5.20372</syntaxhighlight>
Or
<syntaxhighlight lang=J> 9!:11]10 NB. display 10 digits of floating point precision
hsahoeg 'gcpue5hp4'
51.43369675 51.43373966
_0.1070737839 _0.1070523262
hsahoeg 'u4pruydqqvj'
57.64910996 57.6491113
5.203719512 5.203720182</syntaxhighlight>
=={{header|jq}}==
'''Adapted from [[#Wren|Wren]] and [[#Python|Python]]'''
{{works with|jq}}
'''Also works with gojq, the Go implementation of jq, and with fq.'''
'''Generic Utilities'''
<syntaxhighlight lang=jq>
def lpad($len; $c): tostring | ($len - length) as $l | ($c * $l)[:$l] + .;
def lpad($len): lpad($len; " ");
def round($digits): pow(10; $digits) as $p | . * $p | round | floor | . / $p;
# Convert the input integer to a string in the specified base (2 to 36 inclusive)
def convert(base):
def stream:
recurse(if . >= base then ./base|floor else empty end) | . % base ;
[stream] | reverse
| if base < 10 then map(tostring) | join("")
elif base <= 36 then map(if . < 10 then 48 + . else . + 87 end) | implode
else error("base too large")
end;
# counting from 0
def enumerate(s): foreach s as $x (-1; .+1; [., $x]);
def to_object(s; o):
reduce s as $x ({}; . + ($x|o));
</syntaxhighlight>
'''GeoHash'''
<syntaxhighlight lang=jq>
def gBase32: "0123456789bcdefghjkmnpqrstuvwxyz";
# Output: the dictionary mapping the characters in gBase32 to bitstrings:
# {"0":"00000", ... "z":"11111"}
def gBase32dict:
to_object( enumerate(gBase32|explode[]|[.]|implode);
{ (.[1]): (.[0]|convert(2)|lpad(5; "0")) } ) ;
def encodeGeohash($location; $prec):
{ latRange: [ -90, 90],
lngRange: [-180, 180],
hash: "",
hashVal: 0,
bits: 0,
even: true
}
| until (.hash|length >= $prec;
.val = if .even then $location[1] else $location[0] end
| .rng = if .even then .lngRange else .latRange end
| .mid = (.rng[0] + .rng[1]) / 2
| if .val > .mid
then .hashVal |= .*2 + 1
| .rng = [.mid, .rng[1]]
| if .even then .lngRange = [.mid, .lngRange[1]] else .latRange = [.mid, .latRange[1]] end
else .hashVal *= 2
| if .even then .lngRange = [.lngRange[0], .mid] else .latRange = [.latRange[0], .mid] end
end
| .even |= not
| if .bits < 4 then .bits += 1
else
.bits = 0
| .hash += gBase32[.hashVal:.hashVal+1]
| .hashVal = 0
end)
| .hash;
def decodeGeohash:
def flip: if . == 0 then 1 else 0 end;
def chars: explode[] | [.] | implode;
# input: a 0/1 string
# output: a stream of 0/1 integers
def bits: explode[] | . - 48;
. as $geo
| gBase32dict as $gBase32dict
| {minmaxes: [[-90.0, 90.0], [-180.0, 180.0]], latlong: 1 }
| reduce ($geo | chars) as $c (.;
reduce ($gBase32dict[$c]|bits) as $bit (.;
.minmaxes[.latlong][$bit|flip] = ((.minmaxes[.latlong] | add) / 2)
| .latlong |= flip))
| .minmaxes ;
def data:
[[51.433718, -0.214126], 2],
[[51.433718, -0.214126], 9],
[[57.64911, 10.40744 ], 11]
;
data
| encodeGeohash(.[0]; .[1]) as $geohash
| (.[0] | map(lpad(10)) | join(",") | "[\(.)]" ) as $loc
| "geohash for \($loc), precision \(.[1]|lpad(3)) = \($geohash)",
" decode => \($geohash|decodeGeohash|map(map(round(6))) )"
</syntaxhighlight>
{{output}}
<pre>
geohash for [ 51.433718, -0.214126], precision 2 = gc
decode => [[50.625,56.25],[-11.25,0]]
geohash for [ 51.433718, -0.214126], precision 9 = gcpue5hp4
decode => [[51.433697,51.43374],[-0.214148,-0.214105]]
geohash for [ 57.64911, 10.40744], precision 11 = u4pruydqqvj
decode => [[57.64911,57.649111],[10.407439,10.40744]]
</pre>
=={{header|Julia}}==
{{trans|Python}}
<syntaxhighlight lang="julia">const ch32 = "0123456789bcdefghjkmnpqrstuvwxyz"
const bool2ch = Dict(string(i-1, base=2, pad=5) => ch for (i, ch) in enumerate(ch32))
const ch2bool = Dict(v => k for (k, v) in bool2ch)
function bisect(val, mn, mx, bits)
mid = (mn + mx) / 2
if val < mid
bits <<= 1 # push 0
mx = mid # range lower half
else
bits = (bits << 1) | 1 # push 1
mn = mid # range upper half
end
return mn, mx, bits
end
function encoder(lat, lng, pre)
latmin, latmax = -90, 90
lngmin, lngmax = -180, 180
bits = Int128(0)
for i in 0:5*pre-1
if i % 2 != 0
# odd bit: bisect latitude
latmin, latmax, bits = bisect(lat, latmin, latmax, bits)
else
# even bit: bisect longitude
lngmin, lngmax, bits = bisect(lng, lngmin, lngmax, bits)
end
end
# Bits to characters
b = string(bits, base=2, pad=5*pre)
geo = [bool2ch[b[i*5+1:i*5+5]] for i in 0:pre-1]
return prod(geo)
end
function decoder(geo)
minmaxes, latlong = [[-90.0, 90.0], [-180.0, 180.0]], 2
for c in geo, bit in ch2bool[c]
minmaxes[latlong][bit == '1' ? 1 : 2] = sum(minmaxes[latlong]) / 2
latlong = 3 - latlong
end
return minmaxes
end
for ((lat, lng), pre) in [([51.433718, -0.214126], 2),
([51.433718, -0.214126], 9),
([57.64911, 10.40744] , 11),
([57.64911, 10.40744] , 22)]
encoded = encoder(lat, lng, pre)
println("encoder(lat=$lat, lng=$lng, pre=$pre) = ", encoded)
println("decoded = ", decoder(encoded))
end
</syntaxhighlight>{{out}}
<pre>
encoder(lat=51.433718, lng=-0.214126, pre=2) = gc
decoded = [[50.625, 56.25], [-11.25, 0.0]]
encoder(lat=51.433718, lng=-0.214126, pre=9) = gcpue5hp4
decoded = [[51.43369674682617, 51.43373966217041], [-0.21414756774902344, -0.21410465240478516]]
encoder(lat=57.64911, lng=10.40744, pre=11) = u4pruydqqvj
decoded = [[57.649109959602356, 57.64911130070686], [10.407439023256302, 10.40744036436081]]
encoder(lat=57.64911, lng=10.40744, pre=22) = u4pruydqqvj8pr9yc27rjr
decoded = [[57.64911, 57.64911000000001], [10.407439999999998, 10.407440000000008]]
</pre>
=={{header|Nim}}==
{{trans|Python}}
{{trans|Julia}}
We omitted the test with precision 22 as it exceeds the capacity of a 64 bits integer.
<syntaxhighlight lang="nim">import math, strformat, strutils, sugar, tables
const
Ch32 = "0123456789bcdefghjkmnpqrstuvwxyz"
Bool2Ch = collect(initTable, for i, ch in Ch32: {i.toBin(5): ch})
Ch2Bool = collect(initTable, for k, v in Bool2Ch: {v: k})
func bisect(val, mn, mx: float; bits: int64): (float, float, int64) =
var
bits = bits
mn = mn
mx = mx
let mid = (mn + mx) * 0.5
if val < mid:
bits = bits shl 1 # push 0.
mx = mid # range lower half.
else:
bits = bits shl 1 or 1 # push 1.
mn = mid # range upper half.
result = (mn, mx, bits)
func encode(lat, long: float; pre: int64): string =
var
(latmin, latmax) = (-90.0, 90.0)
(longmin, longmax) = (-180.0, 180.0)
bits = 0i64
for i in 0..<(5 * pre):
if (i and 1) != 0:
# Odd bit: bisect latitude.
(latmin, latmax, bits) = bisect(lat, latmin, latmax, bits)
else:
# Even bit: bisect longitude.
(longmin, longmax, bits) = bisect(long, longmin, longmax, bits)
# Bits to characters.
let b = bits.toBin(pre * 5)
let geo = collect(newSeq, for i in 0..<pre: Bool2Ch[b[i*5..i*5+4]])
result = geo.join()
func decode(geo: string): array[2, array[2, float]] =
var latlong = 1
result = [[-90.0, 90.0], [-180.0, 180.0]]
for c in geo:
for bit in Ch2Bool[c]:
result[latlong][ord(bit != '1')] = sum(result[latlong]) * 0.5
latlong = 1 - latlong
when isMainModule:
for (lat, long, pre) in [(51.433718, -0.214126, 2),
(51.433718, -0.214126, 9),
(57.64911, 10.40744 , 11)]:
let encoded = encode(lat, long, pre)
echo &"encoder(lat = {lat}, long = {long}, pre = {pre}) = {encoded}"
echo &"decoded = {decode(encoded)}</syntaxhighlight>
{{out}}
<pre>encoder(lat = 51.433718, long = -0.214126, pre = 2) = gc
decoded = [[50.625, 56.25], [-11.25, 0.0]]
encoder(lat = 51.433718, long = -0.214126, pre = 9) = gcpue5hp4
decoded = [[51.43369674682617, 51.43373966217041], [-0.2141475677490234, -0.2141046524047852]]
encoder(lat = 57.64911, long = 10.40744, pre = 11) = u4pruydqqvj
decoded = [[57.64910995960236, 57.64911130070686], [10.4074390232563, 10.40744036436081]]</pre>
=={{header|Perl}}==
{{trans|Raku}}
<syntaxhighlight lang="perl">use strict;
use warnings;
use feature 'say';
use List::AllUtils qw<sum max natatime>;
my @Geo32 = <0 1 2 3 4 5 6 7 8 9 b c d e f g h j k m n p q r s t u v w x y z>;
sub geo_encode {
my( $latitude, $longitude, $precision ) = @_;
my @coord = ($latitude, $longitude);
my @range = ([-90, 90], [-180, 180]);
my($which,$value) = (1, '');
while (length($value) < $precision * 5) {
my $mid = sum(@{$range[$which]}) / 2;
$value .= my $upper = $coord[$which] <= $mid ? 0 : 1;
$range[$which][$upper ? 0 : 1] = $mid;
$which = $which ? 0 : 1;
}
my $enc;
my $iterator = natatime 5, split '', $value;
while (my @n = $iterator->()) {
$enc .= $Geo32[ord pack 'B8', '000' . join '', @n]; # binary to decimal, very specific to the task
}
$enc
}
sub geo_decode {
my($geo) = @_;
my @range = ([-90, 90], [-180, 180]);
my(%Geo32,$c); $Geo32{$_} = $c++ for @Geo32;
my $which = 1;
for ( split '', join '', map { sprintf '%05b', $_ } @Geo32{split '', $geo} ) {
$range[$which][$_] = sum(@{$range[$which]}) / 2;
$which = $which ? 0 : 1;
}
@range
}
for ([51.433718, -0.214126, 2, 'Ireland, most of England and Wales, small part of Scotland'],
[51.433718, -0.214126, 9, "the umpire's chair on Center Court at Wimbledon"],
[51.433718, -0.214126, 17, 'likely an individual molecule of the chair'],
[57.649110, 10.407440, 11, 'Wikipedia test value - Råbjerg Mile in Denmark'],
[59.115800, -151.687312, 7, 'Perl Island, Alaska'],
[38.743586, -109.499336, 8, 'Delicate Arch, Utah'],
) {
my($lat, $long, $precision, $description) = @$_;
my $enc = geo_encode($lat, $long, $precision);
say "\n$lat, $long, $precision ($description):" .
"\ngeo-encoded: $enc\n" .
'geo-decoded: ' . join ', ',
map { sprintf("%.@{[max(3,$precision-3)]}f", ( -($$_[0] + $$_[1]) / 2)) .
' ± ' . sprintf('%.3e', (abs($$_[0] - $$_[1]) / 2))
} geo_decode($enc);}</syntaxhighlight>
{{out}}
<pre>51.433718, -0.214126, 2 (Ireland, most of England and Wales, small part of Scotland):
geo-encoded: gc
geo-decoded: 53.438 ± 2.812e+00, -5.625 ± 5.625e+00
51.433718, -0.214126, 9 (the umpire's chair on Center Court at Wimbledon):
geo-encoded: gcpue5hp4
geo-decoded: 51.433718 ± 2.146e-05, -0.214126 ± 2.146e-05
51.433718, -0.214126, 17 (likely an individual molecule of the chair):
geo-encoded: gcpue5hp4ebnf8unc
geo-decoded: 51.43371800000523 ± 2.046e-11, -0.21412600000303 ± 2.046e-11
57.64911, 10.40744, 11 (Wikipedia test value - Råbjerg Mile in Denmark):
geo-encoded: u4pruydqqvj
geo-decoded: 57.64911063 ± 6.706e-07, 10.40743969 ± 6.706e-07
59.1158, -151.687312, 7 (Perl Island, Alaska):
geo-encoded: bds0k38
geo-decoded: 59.1154 ± 6.866e-04, -151.6875 ± 6.866e-04
38.743586, -109.499336, 8 (Delicate Arch, Utah):
geo-encoded: 9wfhkm11
geo-decoded: 38.74354 ± 8.583e-05, -109.49919 ± 1.717e-04</pre>
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #008080;">constant</span> <span style="color: #000000;">gBase32</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">"0123456789bcdefghjkmnpqrstuvwxyz"</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">encode_geohash</span><span style="color: #0000FF;">(</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">location</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">integer</span> <span style="color: #000000;">precision</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">r</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{{-</span><span style="color: #000000;">90</span><span style="color: #0000FF;">,</span><span style="color: #000000;">90</span><span style="color: #0000FF;">},{-</span><span style="color: #000000;">180</span><span style="color: #0000FF;">,</span><span style="color: #000000;">180</span><span style="color: #0000FF;">}}</span> <span style="color: #000080;font-style:italic;">-- lat/long</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">ll</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">2</span><span style="color: #0000FF;">,</span> <span style="color: #000080;font-style:italic;">-- " " "</span>
<span style="color: #000000;">hashval</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">bits</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">hash</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">""</span>
<span style="color: #008080;">while</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hash</span><span style="color: #0000FF;">)</span> <span style="color: #0000FF;"><</span> <span style="color: #000000;">precision</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">atom</span> <span style="color: #000000;">mid</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">sum</span><span style="color: #0000FF;">(</span><span style="color: #000000;">r</span><span style="color: #0000FF;">[</span><span style="color: #000000;">ll</span><span style="color: #0000FF;">])/</span><span style="color: #000000;">2</span><span style="color: #0000FF;">,</span>
<span style="color: #000000;">gt</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">location</span><span style="color: #0000FF;">[</span><span style="color: #000000;">ll</span><span style="color: #0000FF;">]></span><span style="color: #000000;">mid</span>
<span style="color: #000000;">hashval</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">hashval</span><span style="color: #0000FF;">*</span><span style="color: #000000;">2</span><span style="color: #0000FF;">+</span><span style="color: #000000;">gt</span>
<span style="color: #000000;">r</span><span style="color: #0000FF;">[</span><span style="color: #000000;">ll</span><span style="color: #0000FF;">][</span><span style="color: #000000;">2</span><span style="color: #0000FF;">-</span><span style="color: #000000;">gt</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">mid</span>
<span style="color: #000000;">bits</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">bits</span><span style="color: #0000FF;">=</span><span style="color: #000000;">5</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">hash</span> <span style="color: #0000FF;">&=</span> <span style="color: #000000;">gBase32</span><span style="color: #0000FF;">[</span><span style="color: #000000;">hashval</span><span style="color: #0000FF;">+</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span>
<span style="color: #0000FF;">{</span><span style="color: #000000;">hashval</span><span style="color: #0000FF;">,</span><span style="color: #000000;">bits</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">0</span><span style="color: #0000FF;">,</span><span style="color: #000000;">0</span><span style="color: #0000FF;">}</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #000000;">ll</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">3</span><span style="color: #0000FF;">-</span><span style="color: #000000;">ll</span> <span style="color: #000080;font-style:italic;">-- (1 <==> 2)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">hash</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #008080;">function</span> <span style="color: #000000;">decode_geohash</span><span style="color: #0000FF;">(</span><span style="color: #004080;">string</span> <span style="color: #000000;">hash</span><span style="color: #0000FF;">)</span>
<span style="color: #000080;font-style:italic;">-- output is {{lat_lo,lat_hi},{long_lo,long_hi}}</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">r</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{{-</span><span style="color: #000000;">90</span><span style="color: #0000FF;">,</span><span style="color: #000000;">90</span><span style="color: #0000FF;">},{-</span><span style="color: #000000;">180</span><span style="color: #0000FF;">,</span><span style="color: #000000;">180</span><span style="color: #0000FF;">}}</span> <span style="color: #000080;font-style:italic;">-- lat/long</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">ll</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">2</span> <span style="color: #000080;font-style:italic;">-- " " "</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">h</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hash</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">b</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">sprintf</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"%05b"</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">find</span><span style="color: #0000FF;">(</span><span style="color: #000000;">hash</span><span style="color: #0000FF;">[</span><span style="color: #000000;">h</span><span style="color: #0000FF;">],</span><span style="color: #000000;">gBase32</span><span style="color: #0000FF;">)-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">it</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #000000;">5</span> <span style="color: #008080;">do</span>
<span style="color: #000000;">r</span><span style="color: #0000FF;">[</span><span style="color: #000000;">ll</span><span style="color: #0000FF;">][</span><span style="color: #000000;">2</span><span style="color: #0000FF;">-(</span><span style="color: #000000;">b</span><span style="color: #0000FF;">[</span><span style="color: #000000;">it</span><span style="color: #0000FF;">]=</span><span style="color: #008000;">'1'</span><span style="color: #0000FF;">)]</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">sum</span><span style="color: #0000FF;">(</span><span style="color: #000000;">r</span><span style="color: #0000FF;">[</span><span style="color: #000000;">ll</span><span style="color: #0000FF;">])/</span><span style="color: #000000;">2</span>
<span style="color: #000000;">ll</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">3</span><span style="color: #0000FF;">-</span><span style="color: #000000;">ll</span> <span style="color: #000080;font-style:italic;">-- (1 <==> 2)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #008080;">return</span> <span style="color: #000000;">r</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">function</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">tests</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{{{</span><span style="color: #000000;">51.433718</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">0.214126</span><span style="color: #0000FF;">},</span> <span style="color: #000000;">2</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{{</span><span style="color: #000000;">51.433718</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">-</span><span style="color: #000000;">0.214126</span><span style="color: #0000FF;">},</span> <span style="color: #000000;">9</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{{</span><span style="color: #000000;">57.64911</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">10.40744</span> <span style="color: #0000FF;">},</span> <span style="color: #000000;">11</span><span style="color: #0000FF;">},</span>
<span style="color: #0000FF;">{{</span><span style="color: #000000;">57.64911</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">10.40744</span> <span style="color: #0000FF;">},</span> <span style="color: #000000;">22</span><span style="color: #0000FF;">}}</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">tests</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #0000FF;">{</span><span style="color: #004080;">sequence</span> <span style="color: #000000;">location</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">integer</span> <span style="color: #000000;">precision</span><span style="color: #0000FF;">}</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">tests</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">geohash</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">encode_geohash</span><span style="color: #0000FF;">(</span><span style="color: #000000;">location</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">precision</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"geohash for %v, precision %d = %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">location</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">precision</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">geohash</span><span style="color: #0000FF;">})</span>
<span style="color: #000000;">tests</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">geohash</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"\ndecode tests:\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">tests</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">append</span><span style="color: #0000FF;">(</span><span style="color: #000000;">tests</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"ezs42"</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">tests</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"%-22s ==> %v\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">tests</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">],</span><span style="color: #000000;">decode_geohash</span><span style="color: #0000FF;">(</span><span style="color: #000000;">tests</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">])})</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
geohash for {51.433718,-0.214126}, precision 2 = gc
geohash for {51.433718,-0.214126}, precision 9 = gcpue5hp4
geohash for {57.64911,10.40744}, precision 11 = u4pruydqqvj
geohash for {57.64911,10.40744}, precision 22 = u4pruydqqvj8pr9yc27rjr
decode tests:
gc ==> {{50.625,56.25},{-11.25,0}}
gcpue5hp4 ==> {{51.43369675,51.43373966},{-0.2141475677,-0.2141046524}}
u4pruydqqvj ==> {{57.64910996,57.6491113},{10.40743902,10.40744036}}
u4pruydqqvj8pr9yc27rjr ==> {{57.64911,57.64911},{10.40744,10.40744}}
ezs42 ==> {{42.58300781,42.62695312},{-5.625,-5.581054688}}
</pre>
Not surprisingly, given the area it covers, "gc" is not even accurate to one significant digit, but a precision of 9 is accurate to 5 or 6 significant decimal digits, 11 to 6 or 7 digits, and 22 exceeds the natural 10 sig digs of %v. Note that 32-bit gives a last character of 'q' for the precision 22 test, for obvious reasons. The above results are from using the 64-bit interpreter.
=={{header|PicoLisp}}==
<syntaxhighlight lang="picolisp">(scl 20)
(setq *GBASE32 (chop "0123456789bcdefghjkmnpqrstuvwxyz"))
(de encode (Lat Lng Prec)
(let
(Base (circ (list -180.0 180.0) (list -90.0 90.0))
Curr (circ Lng Lat)
Lst
(make
(do (* 5 Prec)
(let
(B (++ Base)
C (++ Curr)
M (/ (sum prog B) 2) )
(if (> C M)
(prog (set B M) (link 1))
(set (cdr B) M)
(link 0) ) ) ) ) )
(pack
(make
(for (L Lst L)
(link
(get
*GBASE32
(inc (bin (pack (cut 5 'L)))) ) ) ) ) ) ) )
(println (encode 51.433718 -0.214126 2))
(println (encode 51.433718 -0.214126 9))
(println (encode 57.649110 10.407440 11))</syntaxhighlight>
{{out}}
<pre>
"gc"
"gcpue5hp4"
"u4pruydqqvj"
</pre>
=={{header|Python}}==
<syntaxhighlight lang="python">ch32 = "0123456789bcdefghjkmnpqrstuvwxyz"
bool2ch = {f"{i:05b}": ch for i, ch in enumerate(ch32)}
ch2bool = {v : k for k, v in bool2ch.items()}
def bisect(val, mn, mx, bits):
mid = (mn + mx) / 2
if val < mid:
bits <<= 1 # push 0
mx = mid # range lower half
else:
bits = bits << 1 | 1 # push 1
mn = mid # range upper half
return mn, mx, bits
def encoder(lat, lng, pre):
latmin, latmax = -90, 90
lngmin, lngmax = -180, 180
bits = 0
for i in range(pre * 5):
if i % 2:
# odd bit: bisect latitude
latmin, latmax, bits = bisect(lat, latmin, latmax, bits)
else:
# even bit: bisect longitude
lngmin, lngmax, bits = bisect(lng, lngmin, lngmax, bits)
# Bits to characters
b = f"{bits:0{pre * 5}b}"
geo = (bool2ch[b[i*5: (i+1)*5]] for i in range(pre))
return ''.join(geo)
def decoder(geo):
minmaxes, latlong = [[-90.0, 90.0], [-180.0, 180.0]], True
for c in geo:
for bit in ch2bool[c]:
minmaxes[latlong][bit != '1'] = sum(minmaxes[latlong]) / 2
latlong = not latlong
return minmaxes
if __name__ == '__main__':
for (lat, lng), pre in [([51.433718, -0.214126], 2),
([51.433718, -0.214126], 9),
([57.64911, 10.40744] , 11),
([57.64911, 10.40744] , 22)]:
print("encoder(lat=%f, lng=%f, pre=%i) = %r"
% (lat, lng, pre, encoder(lat, lng, pre)))</syntaxhighlight>
{{out}}
<pre>encoder(lat=51.433718, lng=-0.214126, pre=2) = 'gc'
encoder(lat=51.433718, lng=-0.214126, pre=9) = 'gcpue5hp4'
encoder(lat=57.649110, lng=10.407440, pre=11) = 'u4pruydqqvj'
encoder(lat=57.649110, lng=10.407440, pre=22) = 'u4pruydqqvj8pr9yc27rjr'</pre>
Note: The precision can be increased but would need latitude and longitude expressed with more precision than floats, such as fractions or decimals, for more accurate results. Due to duck typing, the encoder function would not need changing, though.
=={{header|Raku}}==
===Module based===
Reference: Used [https://www.movable-type.co.uk/scripts/geohash.html this] for verification.
<syntaxhighlight lang="raku" line>#20200615 Raku programming solution
use Geo::Hash;
# task example 1 : Ireland, most of England and Wales, small part of Scotland
say geo-encode(51.433718e0, -0.214126e0, 2);
# task example 2 : the umpire's chair on Center Court at Wimbledon
say geo-encode(51.433718e0, -0.214126e0, 9);
# Lake Raku is an artificial lake in Tallinn, Estonia
# https://goo.gl/maps/MEBXXhiFbN8WMo5z8
say geo-encode(59.358639e0, 24.744778e0, 4);
# Village Raku is a development committee in north-western Nepal
# https://goo.gl/maps/33s7k2h3UrHCg8Tb6
say geo-encode(29.2021188e0, 81.5324561e0, 4);</syntaxhighlight>
{{out}}
<pre>gc
gcpue5hp4
ud99
tv1y
</pre>
===Roll your own===
Alternately, a roll-your-own version that will work with any Real coordinate, not just floating point values, and thus can return ridiculous precision.
The geo-decode routine returns the range in which the actual value will be found; converted here to the mid-point with the interval size. Probably better
to specify an odd precision so the error interval ends up the same for both latitude and longitude.
<syntaxhighlight lang="raku" line>my @Geo32 = <0 1 2 3 4 5 6 7 8 9 b c d e f g h j k m n p q r s t u v w x y z>;
sub geo-encode ( Rat(Real) $latitude, Rat(Real) $longitude, Int $precision = 9 ) {
my @coord = $latitude, $longitude;
my @range = [-90, 90], [-180, 180];
my $which = 1;
my $value = '';
while $value.chars < $precision * 5 {
my $mid = @range[$which].sum / 2;
$value ~= my $upper = +(@coord[$which] > $mid);
@range[$which][not $upper] = $mid;
$which = not $which;
}
@Geo32[$value.comb(5)».parse-base(2)].join;
}
sub geo-decode ( Str $geo ) {
my @range = [-90, 90], [-180, 180];
my $which = 1;
my %Geo32 = @Geo32.antipairs;
for %Geo32{$geo.comb}».fmt('%05b').join.comb {
@range[$which][$_] = @range[$which].sum / 2;
$which = not $which;
}
@range
}
# TESTING
for 51.433718, -0.214126, 2, # Ireland, most of England and Wales, small part of Scotland
51.433718, -0.214126, 9, # the umpire's chair on Center Court at Wimbledon
51.433718, -0.214126, 17, # likely an individual molecule of the chair
57.649110, 10.407440, 11, # Wikipedia test value - Råbjerg Mile in Denmark
59.358639, 24.744778, 7, # Lake Raku in Estonia
29.2021188, 81.5324561, 7 # Village Raku in Nepal
-> $lat, $long, $precision {
say "$lat, $long, $precision:\ngeo-encoded: ",
my $enc = geo-encode $lat, $long, $precision;
say 'geo-decoded: ', geo-decode($enc).map( {-.sum/2 ~ ' ± ' ~
(abs(.[0]-.[1])/2).Num.fmt('%.3e')} ).join(', ') ~ "\n";
}</syntaxhighlight>
<pre>51.433718, -0.214126, 2:
geo-encoded: gc
geo-decoded: 53.4375 ± 2.813e+00, -5.625 ± 5.625e+00
51.433718, -0.214126, 9:
geo-encoded: gcpue5hp4
geo-decoded: 51.4337182 ± 2.146e-05, -0.21412611 ± 2.146e-05
51.433718, -0.214126, 17:
geo-encoded: gcpue5hp4ebnf8unc
geo-decoded: 51.43371800000523 ± 2.046e-11, -0.21412600000303 ± 2.046e-11
57.64911, 10.40744, 11:
geo-encoded: u4pruydqqvj
geo-decoded: 57.64911063 ± 6.706e-07, 10.407439694 ± 6.706e-07
59.358639, 24.744778, 7:
geo-encoded: ud99ejf
geo-decoded: 59.358444 ± 6.866e-04, 24.744644 ± 6.866e-04
29.2021188, 81.5324561, 7:
geo-encoded: tv1ypk4
geo-decoded: 29.202347 ± 6.866e-04, 81.532974 ± 6.866e-04
</pre>
=={{header|RPL}}==
{{trans|Python}}
{{works with|HP|48}}
« ROT ROT DUP ∑LIST 2 /
ROT OVER <
ROT OVER 1 + 4 ROLL PUT
ROT SL ROT NOT R→B OR
» '<span style="color:blue">BISECT</span>' STO <span style="color:grey">''@ ( val (mn,mx) bits → (a,b) bits )''</span>
« "0123456789bcdefghjkmnpqrstuvwxyz" "" → coord pre ch32 hash
« { -90 90 } { -180 180 } #0
0 pre 5 * 1 - FOR j
'''IF''' j 2 MOD '''THEN'''
coord 1 GET 4 ROLL ROT <span style="color:blue">BISECT</span> ROT SWAP
'''ELSE'''
coord 2 GET ROT ROT <span style="color:blue">BISECT</span>
'''END'''
'''NEXT'''
1 pre '''START'''
ch32 OVER #31d AND B→R 1 + DUP SUB
'hash' STO+ 32 /
'''NEXT'''
3 DROPN hash
» » '<span style="color:blue">→GEOH</span>' STO <span style="color:grey">''@ ( { lat long } pre → "geohash" )''</span>
« "0123456789bcdefghjkmnpqrstuvwxyz" "" → hash ch32
« "" BIN
1 hash SIZE '''FOR''' j
ch32 hash j DUP SUB POS
1 - 32 + R→B →STR 4 OVER SIZE 1 - SUB +
'''NEXT'''
'hash' STO
{ {-90,90} {-180,180} }
1 hash SIZE '''FOR''' j
j 2 MOD 1 + DUP2 GET
hash j DUP SUB "0" == 1 +
OVER ∑LIST 2 / PUT PUT
'''NEXT'''
» » '<span style="color:blue">GEOH→</span>' STO <span style="color:grey">''@ ( "geohash" → { { latmin latmax } { longmin longmax ) }''</span>
{ 51.433718 -0.214126 } 2 <span style="color:blue">GEOH→</span>
{ 51.433718 -0.214126 } 9 <span style="color:blue">GEOH→</span>
{ 57.649110 10.407440 } 11 <span style="color:blue">GEOH→</span>
{{out}}
<pre>
3: "gc"
2: "gcpuxe0rj"
1: "u4pruydqqvj"
</pre>
RPL floating-point numbers have only 12 significant digits, which could explain the error in the second case.
"gc" <span style="color:blue">GEOH→</span>
"gcpue5hp4" <span style="color:blue">GEOH→</span>
"u4pruydqqvj" <span style="color:blue">GEOH→</span>
{{out}}
<pre>
3: { { 50.625 56.25 } { -11.25 0 } }
2: { { 51.4336967465 51.433739662 } { -.21414756775 -.214104652406 } }
1: { { 57.6491099595 57.649111301 } { 10.4074390233 10.4074403644 } }
</pre>
=={{header|Scala}}==
{{trans|Swift}}
<syntaxhighlight lang="Scala">
object Base32 {
val base32 = "0123456789bcdefghjkmnpqrstuvwxyz" // no "a", "i", "l", or "o"
}
case class Coordinate(latitude: Double, longitude: Double) {
override def toString: String = {
val latitudeHemisphere = if (latitude < 0) " S" else " N"
val longitudeHemisphere = if (longitude < 0) " W" else " E"
s"${math.abs(latitude)}$latitudeHemisphere, ${math.abs(longitude)}$longitudeHemisphere"
}
}
object GeoHashEncoder {
def encodeGeohash(coordinate: Coordinate, precision: Int = 9): String = {
var latitudeRange: (Double, Double) = (-90.0, 90.0)
var longitudeRange: (Double, Double) = (-180.0, 180.0)
var hash = ""
var hashVal = 0
var bits = 0
var even = true
while (hash.length < precision) {
val valCoord = if (even) coordinate.longitude else coordinate.latitude
val (rangeStart, rangeEnd) = if (even) longitudeRange else latitudeRange
val mid = (rangeStart + rangeEnd) / 2
if (valCoord > mid) {
hashVal = (hashVal << 1) + 1
if (even) longitudeRange = (mid, rangeEnd) else latitudeRange = (mid, rangeEnd)
} else {
hashVal = (hashVal << 1)
if (even) longitudeRange = (rangeStart, mid) else latitudeRange = (rangeStart, mid)
}
even = !even
if (bits < 4) {
bits += 1
} else {
bits = 0
hash += Base32.base32.charAt(hashVal)
hashVal = 0
}
}
hash
}
}
object Main extends App {
val coordinate1 = Coordinate(51.433718, -0.214126)
val coordinate2 = Coordinate(57.649110, 10.407440)
println(s"Geohash for: ${coordinate1.toString}, precision = 5 : ${GeoHashEncoder.encodeGeohash(coordinate1, 5)}")
println(s"Geohash for: ${coordinate1.toString}, precision = 9 : ${GeoHashEncoder.encodeGeohash(coordinate1)}")
println(s"Geohash for: ${coordinate2.toString}, precision = 11 : ${GeoHashEncoder.encodeGeohash(coordinate2, 11)}")
}
</syntaxhighlight>
{{out}}
<pre>
Geohash for: 51.433718 N, 0.214126 W, precision = 5 : gcpue
Geohash for: 51.433718 N, 0.214126 W, precision = 9 : gcpue5hp4
Geohash for: 57.64911 N, 10.40744 E, precision = 11 : u4pruydqqvj
</pre>
=={{header|Swift}}==
<syntaxhighlight lang="swift">let base32 = "0123456789bcdefghjkmnpqrstuvwxyz" // no "a", "i", "l", or "o"
extension String {
subscript(i: Int) -> String {
String(self[index(startIndex, offsetBy: i)])
}
}
struct Coordinate {
var latitude: Double
var longitude: Double
func toString() -> String {
var latitudeHemisphere = ""
var longitudeHemisphere = ""
latitudeHemisphere = latitude < 0 ? " S" : " N"
longitudeHemisphere = longitude < 0 ? " W" : " E"
return "\(abs(latitude))\(latitudeHemisphere), \(abs(longitude))\(longitudeHemisphere)"
}
}
func encodeGeohash (for
var latitudeRange = -90.0...90.0
var longitudeRange = -180...180.0
Line 113 ⟶ 1,146:
while (hash.count < precision) {
let val = even ?
var range = even ? longitudeRange : latitudeRange
let mid = (range.lowerBound + range.upperBound) / 2
Line 122 ⟶ 1,155:
if even { longitudeRange = mid...longitudeRange.upperBound }
else { latitudeRange
} else {
hashVal = (hashVal << 1) + 0
if even { longitudeRange = longitudeRange.lowerBound...mid }
else { latitudeRange = latitudeRange.lowerBound...mid }
}
Line 135 ⟶ 1,170:
} else {
bits = 0
hash +=
hashVal = 0
}
}
return hash
}
let coordinate1 = Coordinate(latitude: 51.433718, longitude: -0.214126)
let coordinate2 = Coordinate(latitude: 57.649110, longitude: 10.407440)
print ("Geohash for: \(coordinate1.toString()), precision = 5 : \(encodeGeohash(for: coordinate, withPrecision: 5))")
print ("Geohash for: \(coordinate1.toString()), precision = 9 : \(encodeGeohash(for: coordinate))")
print ("Geohash for: \(coordinate2.toString()), precision = 11 : \(encodeGeohash(for: coordinate, withPrecision: 11))")
</syntaxhighlight>
{{out}}
<pre>
Geohash for: 51.433718 N, 0.214126 W, precision = 5 : gcpue
Geohash for: 51.433718 N, 0.214126 W, precision = 9 : gcpue5hp4
Geohash for: 57.64911 N, 10.40744 E, precision = 11 : u4pruydqqvj
</pre>
=={{header|V (Vlang)}}==
{{trans|go}}
<syntaxhighlight lang="v (vlang)">struct Location {
lat f64
lng f64
}
fn (loc Location) str() string { return "[$loc.lat, $loc.lng]" }
struct Range {
lower f64
upper f64
}
const g_base32 = "0123456789bcdefghjkmnpqrstuvwxyz"
fn encode_geo_hash(loc Location, prec int) string {
mut lat_range := Range{-90, 90}
mut lng_range := Range{-180, 180}
mut hash := ''
mut hash_val := u32(0)
mut bits := 0
mut even := true
for hash.len < prec {
mut val := loc.lat
mut rng := lat_range
if even {
val = loc.lng
rng = lng_range
}
mid := (rng.lower + rng.upper) / 2
if val > mid {
hash_val = (hash_val << 1) + 1
rng = Range{mid, rng.upper}
if even {
lng_range = Range{mid, lng_range.upper}
} else {
lat_range = Range{mid, lat_range.upper}
}
} else {
hash_val <<= 1
if even {
lng_range = Range{lng_range.lower, mid}
} else {
lat_range = Range{lat_range.lower, mid}
}
}
even = !even
if bits < 4 {
bits++
} else {
bits = 0
hash+=g_base32[hash_val..hash_val+1]
hash_val = u32(0)
}
}
return hash.str()
}
fn main() {
locs := [Location{51.433718, -0.214126},
Location{51.433718, -0.214126},
Location{57.64911, 10.40744},
]
precs := [2, 9, 11]
for i, loc in locs {
geohash := encode_geo_hash(loc, precs[i])
println("geohash for $loc, precision ${precs[i]:-2} = $geohash")
}
}</syntaxhighlight>
{{out}}
<pre>geohash for [51.433718, -0.214126], precision 2 = gc
geohash for [51.433718, -0.214126], precision 9 = gcpue5hp4
geohash for [57.649110, 10.407440], precision 11 = u4pruydqqvj</pre>
=={{header|Wren}}==
{{trans|Swift}}
{{libheader|Wren-fmt}}
<
var gBase32 = "0123456789bcdefghjkmnpqrstuvwxyz"
Line 190 ⟶ 1,317:
var loc = "[%(Fmt.f(9, d[0][0], 6)), %(Fmt.f(9, d[0][1], 6))]"
System.print("geohash for %(loc), precision %(Fmt.d(-2, d[1])) = %(geohash)")
}</
{{out}}
| |||