Three word location: Difference between revisions
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=={{header|Wren}}== |
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{{libheader|Wren-fmt}} |
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{{libheader|Wren-big}} |
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This just follows the steps in the task description though I couldn't see any point in creating a 28,126 element array when two simple functions will do. |
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Note that bitwise operations are limited to 32-bit unsigned integers in Wren which isn't big enough here so we use BigInts instead. |
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<lang ecmascript>import "/fmt" for Fmt |
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import "/big" for BigInt |
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// functions to convert to and from the word format 'W00000' |
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var toWord = Fn.new { |w| Fmt.swrite("W$05d", w) } |
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var fromWord = Fn.new { |w| Num.fromString(w[1..-1]) } |
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// set latitude and longitude and print them |
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System.print("Starting figures:") |
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var lat = 28.3852 |
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var lon = -81.5638 |
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Fmt.print(" latitude = $0.4f, longitude = $0.4f", lat, lon) |
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// convert lat and lon to positive BigInts |
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var ilat = BigInt.new(lat * 10000 + 900000) |
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var ilon = BigInt.new(lon * 10000 + 1800000) |
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// build 43 bit BigInt comprising 21 bits (lat) and 22 bits (lon) |
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var latlon = (ilat << 22) + ilon |
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// isolate relevant bits and convert back to 'normal' ints |
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var w1 = ((latlon >> 28) & 0xefff).toSmall |
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var w2 = ((latlon >> 14) & 0x7fff).toSmall |
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var w3 = (latlon & 0x7fff).toSmall |
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// convert to word format |
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w1 = toWord.call(w1) |
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w2 = toWord.call(w2) |
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w3 = toWord.call(w3) |
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// and print the results |
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System.print("\nThree word location is:") |
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Fmt.print(" $s $s $s", w1, w2, w3) |
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/* now reverse the procedure */ |
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w1 = BigInt.new(fromWord.call(w1)) |
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w2 = BigInt.new(fromWord.call(w2)) |
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w3 = BigInt.new(fromWord.call(w3)) |
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latlon = (w1 << 28) | (w2 << 14) | w3 |
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ilat = (latlon >> 22).toSmall |
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ilon = (latlon & 0xfffff).toSmall |
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lat = (ilat - 900000) / 10000 |
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lon = (ilon - 1800000) / 10000 |
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// and print the results |
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System.print("\nAfter reversing the procedure:") |
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Fmt.print(" latitude = $0.4f, longitude = $0.4f", lat, lon)</lang> |
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{{out}} |
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<pre> |
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Starting figures: |
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latitude = 28.3852, longitude = -81.5638 |
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Three word location is: |
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W18497 W27708 W01322 |
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After reversing the procedure: |
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latitude = 28.3852, longitude = -81.5638 |
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</pre> |
Revision as of 10:03, 20 July 2020
Three Word Location. Display a location on the Earth with three words derived from a latitude longitude pair. For: latitude = 28.3852 longitude = -81.5638 Display: W18497 W11324 W01322 Implementation: Build a synthetic word array of 28126, 6 character words in the form W00000 thru W28125. Convert latitude and longitude into positive integers. Build a 43 bit integer containing latitude (21 bits) and longitude (22 bits). Isolate most significant 15 bits for word 1 index. Isolate next 14 bits for word 2 index. Isolate next 14 bits for word 3 index. Fetch each word from the word array. Display the words. Reverse the procedure and display the original latitude and longitude.
Julia
Direct translation from the SymSyn example given by the task creator. though note that idiomatic Julia would usually code this as two small encode() and decode() functions. <lang julia>
- Three Word Location - convert latitude and longitude to three words
LAT = 28.3852 LON = -81.5638
- build word array W00000 ... W28125
wordarray = ["W" * string(x, pad=5) for x in 0:28125]
- make latitude and longitude positive integers
ILAT = Int(LAT * 10000 + 900000) ILON = Int(LON * 10000 + 1800000)
- build 43 bit integer containing latitude (21 bits) and longitude (22 bits)
LATLON = (ILAT << 22) + ILON
- isolate most significant 15 bits for word 1 index
- next 14 bits for word 2 index
- next 14 bits for word 3 index
W1 = (LATLON >> 28) & 0xefff W2 = (LATLON >> 14) & 0x7fff W3 = LATLON & 0x7fff
- fetch each word from word array
w1 = wordarray[W1 + 1] w2 = wordarray[W2 + 1] w3 = wordarray[W3 + 1]
- display words
println("$w1 $w2 $w3")
- reverse the procedure
- look up each word
(w1index, w2index, w3index) = indexin([w1, w2, w3], wordarray) .- 1
- build the latlon integer from the word indexes
latlon = (w1index << 28) | (w2index << 14) | w3index
- isolate the latitude and longitude
ilon = latlon & 0xfffff ilat = latlon >> 22
- convert back to floating point values
lon = (ilon - 1800000) / 10000 lat = (ilat - 900000) / 10000
- display values
println("latitude = $lat longitude = $lon")
</lang>
- Output:
W18497 W27708 W01322 latitude = 28.3852 longitude = -81.5638
Idiomatic version
Output is the same as direct translation version. <lang julia> const LAT = 28.3852 const LON = -81.5638
- build word array W00000 ... W28125
const wordarray = ["W" * string(x, pad=5) for x in 0:28125]
function threewordencode(lat, lon) # returns vector of 3 strings
i = (Int(lat * 10000 + 900000) << 22) | Int(lon * 10000 + 1800000) return map(x -> wordarray[x + 1], [(i >> 28) & 0xefff, (i >> 14) & 0x7fff, i & 0x7fff])
end
words = threewordencode(LAT, LON) println(join(words, " "))
function threeworddecode(w1, w2, w3) # returns pair of Float64
(i1, i2, i3) = indexin([w1, w2, w3], wordarray) .- 1 latlon = (i1 << 28) | (i2 << 14) | i3 ilon, ilat = latlon & 0xfffff, latlon >> 22 return (ilon - 1800000) / 10000, (ilat - 900000) / 10000
end
lat, lon = threeworddecode(words...) println("latitude = $lat longitude = $lon") </lang>
Symsyn
<lang Symsyn> | Three Word Location - convert latitude and longitude to three words
lat : 28.3852 lon : -81.5638
| build word array W00000 ... W28125
i if i <= 28125 ~ i $r #$r szr 'W00000' $t (6-szr) szr szr #$t + $r $t + $t $wordarray + i goif endif
| make latitude and longitude positive integers
{lat * 10000 + 900000} ilat {lon * 10000 + 1800000} ilon
| build 43 bit integer containing latitude (21 bits) and longitude (22 bits)
ilat latlon shl latlon 22 + ilon latlon
| isolate most significant 15 bits for word 1 index | next 14 bits for word 2 index | next 14 bits for word 3 index
latlon:42:15 w1 latlon:27:14 w2 latlon:13:14 w3
| fetch each word from word array
(w1*6+1) w1 $wordarray.w1 $w1 6 (w2*6+1) w2 $wordarray.w2 $w2 6 (w3*6+1) w3 $wordarray.w3 $w3 6
| display words
"$w1 ' ' $w2 ' ' $w3" []
| reverse the procedure
| look up each word
call bsearch 0 28125 $w1 result w1index
call bsearch 0 28125 $w2 result w2index
call bsearch 0 28125 $w3 result w3index
| build the latlon integer from the word indexes
w1index latlon shl latlon 14 + w2index latlon shl latlon 14 + w3index latlon
| isolate the latitude and longitude
latlon:21:22 ilon latlon:42:21 ilat
| convert back to floating point values
{(ilon - 1800000) / 10000} lon {(ilat - 900000) / 10000} lat
| display values
"'latitude = ' lat ' longitude = ' lon" []
stop
bsearch
param L H $word if L <= H ((L + H) shr 1) M (M*6+1) I $wordarray.I $w 6 if $w > $word - 1 M H else if $w < $word + 1 M L else return M endif endif goif endif return -1
</lang>
Wren
This just follows the steps in the task description though I couldn't see any point in creating a 28,126 element array when two simple functions will do.
Note that bitwise operations are limited to 32-bit unsigned integers in Wren which isn't big enough here so we use BigInts instead. <lang ecmascript>import "/fmt" for Fmt import "/big" for BigInt
// functions to convert to and from the word format 'W00000' var toWord = Fn.new { |w| Fmt.swrite("W$05d", w) } var fromWord = Fn.new { |w| Num.fromString(w[1..-1]) }
// set latitude and longitude and print them System.print("Starting figures:") var lat = 28.3852 var lon = -81.5638 Fmt.print(" latitude = $0.4f, longitude = $0.4f", lat, lon)
// convert lat and lon to positive BigInts var ilat = BigInt.new(lat * 10000 + 900000) var ilon = BigInt.new(lon * 10000 + 1800000)
// build 43 bit BigInt comprising 21 bits (lat) and 22 bits (lon) var latlon = (ilat << 22) + ilon
// isolate relevant bits and convert back to 'normal' ints var w1 = ((latlon >> 28) & 0xefff).toSmall var w2 = ((latlon >> 14) & 0x7fff).toSmall var w3 = (latlon & 0x7fff).toSmall
// convert to word format w1 = toWord.call(w1) w2 = toWord.call(w2) w3 = toWord.call(w3)
// and print the results System.print("\nThree word location is:") Fmt.print(" $s $s $s", w1, w2, w3)
/* now reverse the procedure */ w1 = BigInt.new(fromWord.call(w1)) w2 = BigInt.new(fromWord.call(w2)) w3 = BigInt.new(fromWord.call(w3)) latlon = (w1 << 28) | (w2 << 14) | w3 ilat = (latlon >> 22).toSmall ilon = (latlon & 0xfffff).toSmall lat = (ilat - 900000) / 10000 lon = (ilon - 1800000) / 10000
// and print the results System.print("\nAfter reversing the procedure:") Fmt.print(" latitude = $0.4f, longitude = $0.4f", lat, lon)</lang>
- Output:
Starting figures: latitude = 28.3852, longitude = -81.5638 Three word location is: W18497 W27708 W01322 After reversing the procedure: latitude = 28.3852, longitude = -81.5638