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Geohash: Difference between revisions
→{{header|Nim}}
Line 218:
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.
<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)}</lang>
{{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}}==
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