Dart - 各種ツール(2線分の交点、例外処理(throw, try/catch/finally))

Dart: Up and Running
(O'Reilly Media)
Kathy Walrath Seth Ladd (著)
[Kindle版]
このブログでの感想

開発環境

• OS X Mavericks - Apple (OS)
• Dart Editor (開発環境)
• Dartium | Dart/ Structured web apps (ブラウザ, Dart VM 用 (Chromium with the Dart VM))
• Safari (ブラウザ, JavaScript 用)
• Dart (プログラミング言語)

初めてのコンピュータサイエンス(Jennifer Campbell、Paul Gries、Jason Montojo、Greg Wilson(著)長尾 高弘(翻訳))の12章(各種ツール)、12.7(練習問題)、12-4、5.をDartで解いてみる。

その他参考書籍

• What is Dart? [Kindle版] (O'Reilly Media) Kathy Walrath Seth Ladd (著) このブログでの感想

12.7(練習問題)、12-4、5.

コード

sample.dart

import 'dart:html';

void main() {
  InputElement run = querySelector('#run_dart');
  InputElement clear = querySelector('#clear');
  Element pre = querySelector('#pre0');
  run.onClick.listen((MouseEvent event){
    pre.text = '${window.navigator.userAgent}\n';
    for(List<List<List<num>>> lines in [[[[0, 0], [1, 1]], [[1, 0], [2, 1]]],
                         [[[0, 0], [1, 1]], [[0, 1], [1, 0]]],
                         [[[0, 0], [1, 1]], [[1, 1], [2, 2]]],
                         [[[0, 0], [1, 1]], [[0, 0], [1, 1]]],
                         [[[0, 0], [2, 2]], [[1, 1], [3, 3]]]]){
      var result;
      try{
          result = lineIntersect(lines.first, lines.last);
      }catch(e){
        result = e;
      } finally {
        pre.text += '$result\n';
      }
    }
  });
  clear.onClick.listen((MouseEvent event) => pre.text = '');
}

lineIntersect(List<List<num>> line1, List<List<num>> line2){
  var new_line1 = newLine(line1);
  var new_line2 = newLine(line2);
  var slope1 = slope(new_line1);
  var slope2 = slope(new_line2);
  var y_intercept1 = yIntercept(new_line1);
  var y_intercept2 = yIntercept(new_line2);
  var infinity = 1 / 0;
  var y1 = slope1 * new_line2[0][0] - y_intercept1;
  var y2 = slope2 * new_line1[0][0] - y_intercept2;
  var x = -(y_intercept1 - y_intercept2) / (slope1 - slope2);
  var y = slope1 * x + y_intercept1;
  if (isEqualLine(new_line1, new_line2)){
    throw "Geometry";
  }
  if (slope1 == slope2){
    if(y_intercept1 == y_intercept2){
      if(new_line1[0][0] > new_line2[1][0] || new_line1[1][0] < new_line2[0][1]){
        return null;
      }
      if (new_line1[0][0] == new_line2[1][0] && new_line1[0][1] == new_line2[1][1]){
        return new_line1[0];
      }
      if(new_line1[1][0] == new_line2[0][0] && new_line1[1][1] == new_line2[0][1]){
        return new_line1.last;
      }
      return line1;
    }
    return null;
  }
  if(slope1 == infinity){
    if(new_line1[0][0] < new_line2[0][0] ||
        new_line1[0][0] > new_line2[1][0] ||
        y2 < new_line1[0][1] || y2 > new_line1[1][1]){
      return null;
    }
    return [new_line1[0][0], y2];
  }
  if(slope2 == infinity){
    if(new_line2[0][0] < new_line1[0][0] ||
        new_line2[0][0] > new_line1[1][0] ||
        y1 < new_line2[0][1] || y1 > new_line2[1][1]){
      return null;
    }
    return [new_line1[0][0], y1];
  }
  if (new_line1[0][0] <= x && x <= new_line1[1][0] && new_line2[0][0] <= x &&
      x <= new_line2[1][0] && min(new_line1[0][1], new_line1[1][1]) <= y &&
      y <= max(new_line1[0][1], new_line1[1][1]) && min(new_line2[0][1],
          new_line2[1][1]) <= y && y <= max(new_line2[0][1], new_line2[1][1])){
    return [x, y];
  }
  return null;
}

List<List<num>> newLine(List<List<num>> line){
  List<List<num>> new_line = line;
  var x1 = line[0][0];
  var x2 = line[1][0];
  var y1 = line[0][1];
  var y2 = line[1][1];
  if(x1 > x2 || (x1 == x2 && y1 > y2)){
    new_line = [[x2, y2], [x1, y1]];
  }
  return new_line;
}

num slope(List<List<num>> line){
  var x1 = line[0][0];
  var x2 = line[1][0];
  var y1 = line[0][1];
  var y2 = line[1][1];
  return (y2 - y1) / (x2 - x1);
}
num yIntercept(List<List<num>> line){
  var x = line[0][0];
  var y = line[0][1];
  return y - slope(line) * x;
}

bool isEqualLine(List<List<num>> line1, List<List<num>> line2){
  return isEqual(line1.first, line2.first) &&
      isEqual(line1.last, line2.last);
}
bool isEqual(List s1, List s2){
  if(s1.length != s2.length){
    return false;
  }
  int i;
  for(i = 0; i < s1.length; i += 1){
    if(s1[i] != s2[i]){
      return false;
    }
  }
  return true;
}

num min(num a, num b){
  return a <= b ? a : b;
}

num max(num a, num b){
  return a >= b ? a : b;
}