Geohash: Difference between revisions
Add Scala implementation
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Line 350:
geohash=: {{
bits=.
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
Line 362:
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}}==
Line 378 ⟶ 409:
def convert(base):
def stream:
recurse(if . >=
[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
Line 948 ⟶ 977:
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>
Line 1,111 ⟶ 1,272:
{{trans|Swift}}
{{libheader|Wren-fmt}}
<syntaxhighlight lang="
var gBase32 = "0123456789bcdefghjkmnpqrstuvwxyz"
| |||