200 };

201 }

202 else if (Char(input, '-'))

203 {

204 e = new SubExpression

205 {

206 Left = e,

207 Right = Exp2(input),

208 };

209 }

210 else

211 {

212 break;

213 }

214 }

215 return e;

216 }

217

218 private static Expression UnsafeParse(char* input)

219 {

220 Expression result = Exp3(&input);

221 if ((int)*input == 0)

222 {

223 return result;

224 }

225 else

226 {

227 throw new ArgumentException("Expression contains unparsed tail, at " + new string(input));

228 }

229 }

230

231 public static Expression Parse(string s)

232 {

233 fixed (char* input = s.Trim())

234 {

235 return UnsafeParse(input);

236 }

237 }

238 }

239 }

240

下面是运行结果： 1 input: 1

2 parse: 1

3 reparse: 1

4 simplified: 1

5 contains x: False

6 contains y: False

7 dx: 0

8 dy: 0

9 simplified dx: 0

10 simplified dy: 0

11

12 input: 1.2

13 parse: 1.2

14 reparse: 1.2

15 simplified: 1.2

16 contains x: False

17 contains y: False

18 dx: 0

19 dy: 0

20 simplified dx: 0

21 simplified dy: 0

22

23 input: -3

24 parse: -3

25 reparse: -3

26 simplified: -3

27 contains x: False

28 contains y: False

29 dx: -0

30 dy: -0

31 simplified dx: 0

32 simplified dy: 0

33

34 input: 12+34

35 parse: (12 + 34)

36 reparse: (12 + 34)

37 simplified: 46

38 contains x: False

39 contains y: False

40 dx: (0 + 0)

41 dy: (0 + 0)

42 simplified dx: 0

43 simplified dy: 0

44

45 input: 56*78

46 parse: (56 * 78)

47 reparse: (56 * 78)

48 simplified: 4368

49 contains x: False

50 contains y: False

51 dx: ((0 * 78) + (56 * 0))

52 dy: ((0 * 78) + (56 * 0))

53 simplified dx: 0

54 simplified dy: 0

55

56 input: x^y

57 parse: (x ^ y)

58 reparse: (x ^ y)

59 simplified: (x ^ y)

60 contains x: True

61 contains y: True

62 dx: (y * (x ^ (y - 1)))

63 dy: ((x ^ y) * ln(x))

64 simplified dx: (y * (x ^ (y - 1)))

65 simplified dy: ((x ^ y) * ln(x))

66

67 input: x+2*y+4

68 parse: ((x + (2 * y)) + 4)

69 reparse: ((x + (2 * y)) + 4)

70 simplified: ((x + (2 * y)) + 4)

71 contains x: True

72 contains y: True

73 dx: ((1 + ((0 * y) + (2 * 0))) + 0)

74 dy: ((0 + ((0 * y) + (2 * 1))) + 0)

75 simplified dx: 1

76 simplified dy: 2

77

78 input: (x+y)*(3+4)

79 parse: ((x + y) * (3 + 4))

80 reparse: ((x + y) * (3 + 4))

81 simplified: ((x + y) * 7)

82 contains x: True

83 contains y: True

84 dx: (((1 + 0) * (3 + 4)) + ((x + y) * (0 + 0)))