Modify integer conversion for dart implementation (#700)

* Modify dart implementation

* update dart workflow to use dart commands

* remove change to tests to force them to fail

* update checks script for new dart commands

* modify integer conversion in dart library

* fix % operator behaviour and formatting

* update dart commands

* dart format fixes

Author: drinckes

.github/workflows/main.yml

@@ -38,7 +38,7 @@ jobs:
       - name: test
         run: |
           cd ${OLC_PATH}
-          pub get && pub run test
+          dart pub get && dart test
           bash checks.sh
 
   # Go implementation. Lives in go/. Tests fail if files have not been formatted with gofmt.

dart/README.md

@@ -2,12 +2,12 @@
 
 ## Formatting
 
-Code **must** be formatted using `dartfmt`.
+Code **must** be formatted using `dart format`.
 
-To format your files, just run `format_check.sh` or:
+To format your files, just run `checks.sh` or:
 
-```
-dartfmt --fix --overwrite .
+```shell
+dart format .
 ```
 
 The TravisCI test **will fail if any files need formatting**.
@@ -24,5 +24,5 @@ To test the dart version first download the dart sdk from
 directory:
 
 ```
-~/open-location-code$ cd dart && pub run test
+~/open-location-code$ cd dart && dart test
 ```

dart/checks.sh

@@ -3,29 +3,23 @@
 # with dartanalyzer.
 # Run from within the dart directory.
 
-DART_FMT_CMD=dartfmt
-$DART_FMT_CMD --version >/dev/null 2>&1
+DART_CMD=dart
+$DART_CMD --version >/dev/null 2>&1
 if [ $? -ne 0 ]; then
-  DART_FMT_CMD=/usr/lib/dart/bin/dartfmt
-fi
-
-DART_ANALYZER_CMD=dartanalyzer
-$DART_ANALYZER_CMD --version >/dev/null 2>&1
-if [ $? -ne 0 ]; then
-  DART_ANALYZER_CMD=/usr/lib/dart/bin/dartanalyzer
+  DART_CMD=/usr/lib/dart/bin/dart
 fi
 
 # Define the default return code.
 RETURN=0
 
 # For every dart file, check the formatting.
 for FILE in `find * | egrep "\.dart$"`; do
-  FORMATTED=`$DART_FMT_CMD --set-exit-if-changed --fix "$FILE"`
+  FORMATTED=`$DART_CMD format -o none --set-exit-if-changed "$FILE"`
   if [ $? -ne 0 ]; then
     if [ -z "$TRAVIS" ]; then
       # Running locally, we can just format the file. Use colour codes.
       echo -e "\e[1;34m"
-      $DART_FMT_CMD --fix --overwrite $FILE
+      $DART_CMD format $FILE
       echo -e "\e[0m"
     else
       # On TravisCI, send a comment with the diff to the pull request.
@@ -39,7 +33,7 @@ for FILE in `find * | egrep "\.dart$"`; do
           --commit "$TRAVIS_PULL_REQUEST_SHA"
     fi
   fi
-  ANALYSIS=`$DART_ANALYZER_CMD "$FILE"`
+  ANALYSIS=`$DART_CMD analyze "$FILE"`
   echo "$ANALYSIS" | grep "No issues found" >/dev/null
   if [ $? -ne 0 ]; then
     echo -e "\e[1;31mStatic analysis problems: $FILE\e[0m"

dart/lib/src/open_location_code.dart

@@ -108,7 +108,7 @@ bool _matchesPattern(String string, Pattern pattern) =>
     string.contains(pattern);
 
 bool isValid(String code) {
-  if (code == null || code.length == 1) {
+  if (code.length == 1) {
     return false;
   }
 
@@ -254,33 +254,40 @@ bool isFull(String code) {
 /// * [codeLength]: The number of significant digits in the output code, not
 /// including any separator characters.
 String encode(num latitude, num longitude, {int codeLength = pairCodeLength}) {
-  if (codeLength < minDigitCount || (codeLength < pairCodeLength && codeLength.isOdd)) {
+  if (codeLength < minDigitCount ||
+      (codeLength < pairCodeLength && codeLength.isOdd)) {
     throw ArgumentError('Invalid Open Location Code length: $codeLength');
   }
   codeLength = min(maxDigitCount, codeLength);
-  // Ensure that latitude and longitude are valid.
-  latitude = clipLatitude(latitude);
-  longitude = normalizeLongitude(longitude);
-  // Latitude 90 needs to be adjusted to be just less, so the returned code
-  // can also be decoded.
-  if (latitude == 90) {
-    latitude -= computeLatitudePrecision(codeLength).toDouble();
-  }
-  var code = '';
 
-  // Compute the code.
   // This approach converts each value to an integer after multiplying it by
   // the final precision. This allows us to use only integer operations, so
   // avoiding any accumulation of floating point representation errors.
 
-  // Multiply values by their precision and convert to positive.
-  // Force to integers so the division operations will have integer results.
-  // Note: Dart requires rounding before truncating to ensure precision!
-  var latVal =
-      ((latitude + latitudeMax) * finalLatPrecision * 1e6).round() ~/ 1e6;
-  var lngVal =
-      ((longitude + longitudeMax) * finalLngPrecision * 1e6).round() ~/ 1e6;
+  // Convert latitude into a positive integer clipped into the range 0-(just
+  // under 180*2.5e7). Latitude 90 needs to be adjusted to be just less, so the
+  // returned code can also be decoded.
+  var latVal = (latitude * finalLatPrecision).round().toInt();
+  latVal += latitudeMax * finalLatPrecision;
+  if (latVal < 0) {
+    latVal = 0;
+  } else if (latVal >= 2 * latitudeMax * finalLatPrecision) {
+    latVal = 2 * latitudeMax * finalLatPrecision - 1;
+  }
+  // Convert longitude into a positive integer and normalise it into the range
+  // 0-360*8.192e6.
+  var lngVal = (longitude * finalLngPrecision).round().toInt();
+  lngVal += longitudeMax * finalLngPrecision;
+  if (lngVal < 0) {
+    // Dart's % operator differs from other languages in that it returns the
+    // same sign as the divisor. This means we don't need to add the range to
+    // the result.
+    lngVal = (lngVal % (2 * longitudeMax * finalLngPrecision));
+  } else if (lngVal >= 2 * longitudeMax * finalLngPrecision) {
+    lngVal = lngVal % (2 * longitudeMax * finalLngPrecision);
+  }
 
+  var code = '';
   // Compute the grid part of the code if necessary.
   if (codeLength > pairCodeLength) {
     for (var i = 0; i < maxDigitCount - pairCodeLength; i++) {
@@ -326,7 +333,8 @@ String encode(num latitude, num longitude, {int codeLength = pairCodeLength}) {
 CodeArea decode(String code) {
   if (!isFull(code)) {
     throw ArgumentError(
-        'Passed Open Location Code is not a valid full code: $code');
+      'Passed Open Location Code is not a valid full code: $code',
+    );
   }
   // Strip out separator character (we've already established the code is
   // valid so the maximum is one), padding characters and convert to upper
@@ -381,8 +389,13 @@ CodeArea decode(String code) {
   var lat = normalLat / pairPrecision + gridLat / finalLatPrecision;
   var lng = normalLng / pairPrecision + gridLng / finalLngPrecision;
   // Return the code area.
-  return CodeArea(lat, lng, lat + latPrecision, lng + lngPrecision,
-      min(code.length, maxDigitCount));
+  return CodeArea(
+    lat,
+    lng,
+    lat + latPrecision,
+    lng + lngPrecision,
+    min(code.length, maxDigitCount),
+  );
 }
 
 /// Recover the nearest matching code to a specified location.
@@ -420,7 +433,10 @@ CodeArea decode(String code) {
 /// passed code was not a valid short code, but was a valid full code, it is
 /// returned unchanged.
 String recoverNearest(
-    String shortCode, num referenceLatitude, num referenceLongitude) {
+  String shortCode,
+  num referenceLatitude,
+  num referenceLongitude,
+) {
   if (!isShort(shortCode)) {
     if (isFull(shortCode)) {
       return shortCode.toUpperCase();
@@ -442,9 +458,10 @@ String recoverNearest(
   var halfResolution = resolution / 2.0;
 
   // Use the reference location to pad the supplied short code and decode it.
-  var codeArea = decode(encode(referenceLatitude, referenceLongitude)
-          .substring(0, paddingLength) +
-      shortCode);
+  var codeArea = decode(
+    encode(referenceLatitude, referenceLongitude).substring(0, paddingLength) +
+        shortCode,
+  );
   var centerLatitude = codeArea.center.latitude;
   var centerLongitude = codeArea.center.longitude;
 
@@ -470,8 +487,11 @@ String recoverNearest(
     centerLongitude += resolution;
   }
 
-  return encode(centerLatitude, centerLongitude,
-      codeLength: codeArea.codeLength);
+  return encode(
+    centerLatitude,
+    centerLongitude,
+    codeLength: codeArea.codeLength,
+  );
 }
 
 /// Remove characters from the start of an OLC [code].
@@ -506,8 +526,10 @@ String shorten(String code, num latitude, num longitude) {
   latitude = clipLatitude(latitude);
   longitude = normalizeLongitude(longitude);
   // How close are the latitude and longitude to the code center.
-  var range = max((codeArea.center.latitude - latitude).abs(),
-      (codeArea.center.longitude - longitude).abs());
+  var range = max(
+    (codeArea.center.latitude - latitude).abs(),
+    (codeArea.center.longitude - longitude).abs(),
+  );
   for (var i = pairResolutions.length - 2; i >= 1; i--) {
     // Check if we're close enough to shorten. The range must be less than 1/2
     // the resolution to shorten at all, and we want to allow some safety, so

dart/test/benchmark_test.dart

@@ -26,15 +26,19 @@ void main() {
       olc.encode(testData[i][0], testData[i][1], codeLength: testData[i][2]);
     }
     var duration = stopwatch.elapsedMicroseconds;
-    print('Encoding benchmark ${testData.length}, duration ${duration} usec, '
-        'average ${duration / testData.length} usec');
+    print(
+      'Encoding benchmark ${testData.length}, duration ${duration} usec, '
+      'average ${duration / testData.length} usec',
+    );
 
     stopwatch = Stopwatch()..start();
     for (var i = 0; i < testData.length; i++) {
       olc.decode(testData[i][3]);
     }
     duration = stopwatch.elapsedMicroseconds;
-    print('Decoding benchmark ${testData.length}, duration ${duration} usec, '
-        'average ${duration / testData.length} usec');
+    print(
+      'Decoding benchmark ${testData.length}, duration ${duration} usec, '
+      'average ${duration / testData.length} usec',
+    );
   });
 }