/// <summary>
/// 随机创建表达式树
/// </summary>
public Tuple <Expression, List <ParameterExpression> > Create()
{
//参数名
Queue <string> parameterName =
new Queue <string>(new string[]
{ "a1", "a2",
"b1", "b2",
"c1", "c2",
"d1", "d2",
"e1", "e2",
"f1", "f2",
"g1", "g2",
"h1", "h2",
"i1", "i2",
"j1", "j2",
"k1", "k2",
"l1", "l2",
"m1", "m2",
"n1", "n2",
"o1", "o2",
"p1", "p2" });
Random random = new Random();
int layer = GetTreeLayerCount(random);
//每层使用的队列
Queue <Expression>[] queue = new Queue <Expression> [layer];
for (int i = 0; i < layer; i++)
{
queue[i] = new Queue <Expression>();
}
List <ParameterExpression> parameterList = new List <ParameterExpression>();
for (int l = layer; l >= 1; l--) //自低向上每一层
{
int layerCount = (int)Math.Pow(2, l - 1); //本层的节点数
for (int i = 0; i < layerCount; i++) //每个节点
{
int number = GetExpressionPartNumber(random);
IExpressionPart part = parts.Where(t => t.Number == number).FirstOrDefault();//随机生成一个部件
Expression[] parameter;
Expression expression;
if (layer == l)//最底下一层，直接操作常量的二元运算符
{
string s = parameterName.Dequeue();
var p1 = Expression.Parameter(typeof(int), s);
parameterList.Add(p1);
s = parameterName.Dequeue();
var p2 = Expression.Parameter(typeof(int), s);
parameterList.Add(p2);
parameter = new Expression[] { p1, p2 };
expression = (Activator.CreateInstance(part.GetType()) as IExpressionPart).Process(parameter);
}
else//操作下面一层的二元运算符的结果的表达式
{
parameter = new Expression[] { queue[layer - l - 1].Dequeue(), queue[layer - l - 1].Dequeue() };//从下一层取出两个表达式
expression = (Activator.CreateInstance(part.GetType()) as IExpressionPart).Process(parameter);
}
queue[layer - l].Enqueue(expression);
}
}
return(Tuple.Create(queue[layer - 1].Dequeue(), parameterList));
}
internal virtual Expression Parse(EvaluationContext context, ref string code)
{
if (code == null)
{
throw new ArgumentNullException(nameof(code));
}
IList <ProcessedItem> expressionTree = new List <ProcessedItem>();
IExpressionPart current = GetObject <TParserEntry>();
code = code.TrimStart(context.Whitespaces);
string source = code;
while (!string.IsNullOrEmpty(code))
{
bool found = false;
foreach (Type partType in current.ExpectedParts)
{
IExpressionPart newPart = GetObject(partType);
string part = newPart.Get(context, ref code);
if (!string.IsNullOrEmpty(part))
{
expressionTree.Add(ProcessedItem.Create(partType, part));
current = newPart;
found = true;
break;
}
}
if (!found)
{
string dependentObjects = string.Join(", ",
current.ExpectedParts.Select(o => o.Name)
#if NET35
.ToArray()
#endif
);
throw new EvaluationException($"Invalid expression, unable to parse.\nCurrent part: {current.GetType().Name}\nFollowing parts: {dependentObjects}\n{code}")
{
SourceExpression = source, Position = source.Length - code.Length + 1
};
}
code = code.TrimStart(context.Whitespaces);
}
Expression compiled = Compile(context, expressionTree);
return(compiled);
}
