/// <summary>
/// Compile the single item if it is possible to compile.
/// It concerns those <see cref="ExpressionPart"/>s items which returns expression in <seealso cref="ExpressionPart.GetExpression(EvaluationContext, string, ref ExpressionData)"/>.
/// </summary>
/// <param name="context">The context of evaluation.</param>
/// <param name="expressionTree">The expression tree.</param>
protected virtual bool CompileSingleItem(EvaluationContext context, IList <ProcessedItem> expressionTree)
{
// compile single item
return(ReverseLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (item.ItemType != null)
{
IExpressionPart obj = GetObject(item.ItemType);
ExpressionData data = new ExpressionData();
Expression compiled = obj.GetExpression(context, item.Content, ref data);
if (compiled != null)
{
ProcessedItem newItem = ProcessedItem.Create(compiled);
expressionTree.RemoveAt(i);
expressionTree.Insert(i, newItem);
return true;
}
else if (data.TypeToCast != null)
{
ProcessedItem newItem = ProcessedItem.CreateCast(data.TypeToCast);
expressionTree.RemoveAt(i);
expressionTree.Insert(i, newItem);
return true;
}
}
return false;
}));
}
/// <summary>
/// Compile the binary operators on the same level of priority. It uses the <seealso cref="EvaluationContext.Priority"/> setting.
/// </summary>
/// <param name="context">The context of evaluation.</param>
/// <param name="expressionTree">The expression tree.</param>
/// <param name="priority">The priority level.</param>
/// <returns>True if it changed the expression tree.</returns>
protected virtual bool CompileBinaryOperatorsByPriority(EvaluationContext context, IList <ProcessedItem> expressionTree, int priority) =>
ReverseLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (i > 0 && expressionTree.Count > i + 1 &&
item.ItemType == typeof(EBinaryOperator) &&
expressionTree[i - 1].Expression != null &&
expressionTree[i + 1].Expression != null &&
(context.Priority[priority].Contains(item.Content, StringComparer.OrdinalIgnoreCase)))
{
Expression expr1 = expressionTree[i - 1].Expression;
Expression expr2 = expressionTree[i + 1].Expression;
Type resultType = context.ConsolidateBinaryTypes(context, expr1.Type, expr2.Type);
if ((expr1.Type == typeof(string) || expr1.Type == typeof(char)) && item.Content == "+")
{
resultType = typeof(string);
}
if (expr1.Type != resultType)
{
expr1 = ConvertExpression(expr1, resultType);
}
if (expr2.Type != resultType)
{
expr2 = ConvertExpression(expr2, resultType);
}
Expression expr;
if ((expr1.Type == typeof(string) || expr2.Type == typeof(string)) && item.Content == "+")
{
expr = Expression.Call(StringConcat, new[] { expr1, expr2 });
}
else
{
expr =
Expression.MakeBinary(context.BinaryNodeTypes[item.Content],
expr1,
expr2);
}
ProcessedItem newItem = ProcessedItem.Create(expr);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.Insert(i - 1, newItem);
return(true);
}
return(false);
});
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);
}
/// <summary>
/// Compile the member access.
/// </summary>
/// <param name="expressionTree">The expression tree.</param>
/// <returns>True if it changed the expression tree.</returns>
protected virtual bool CompileMemberAccess(IList <ProcessedItem> expressionTree)
=> ReverseLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (i > 0 &&
item.ItemType == typeof(EMemberAccess) &&
expressionTree[i - 1].Expression != null)
{
Expression expr = expressionTree[i - 1].Expression;
expr = Expression.PropertyOrField(expr, item.Content.Substring(1));
ProcessedItem newItem = ProcessedItem.Create(expr);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.Insert(i - 1, newItem);
return(true);
}
return(false);
});
/// <summary>
/// Compile the conditional operators.
/// </summary>
/// <param name="context">The context of evaluation.</param>
/// <param name="expressionTree">The expression tree.</param>
/// <returns>True if it changed the expression tree.</returns>
protected virtual bool CompileIIfOperators(EvaluationContext context, IList <ProcessedItem> expressionTree) =>
ReverseLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (i > 0 && expressionTree.Count > i + 3 &&
expressionTree[i - 1].Expression != null &&
item.ItemType == typeof(EConditionalOperator) &&
item.Content == "?" &&
expressionTree[i + 1].Expression != null &&
expressionTree[i + 2].ItemType == typeof(EConditionalOperator) &&
expressionTree[i + 2].Content == ":" &&
expressionTree[i + 3].Expression != null
)
{
Expression expr0 = expressionTree[i - 1].Expression;
Expression expr1 = expressionTree[i + 1].Expression;
Expression expr2 = expressionTree[i + 3].Expression;
Type resultType = context.ConsolidateBinaryTypes(context, expr1.Type, expr2.Type);
if (expr1.Type != resultType)
{
expr1 = Expression.Convert(expr1, resultType);
}
if (expr2.Type != resultType)
{
expr2 = Expression.Convert(expr2, resultType);
}
Expression expr = Expression.Condition(expr0, expr1, expr2);
ProcessedItem newItem = ProcessedItem.Create(expr);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.RemoveAt(i - 1);
expressionTree.Insert(i - 1, newItem);
return(true);
}
return(false);
});
/// <summary>
/// Compile the unary operators.
/// </summary>
/// <param name="context">The context of evaluation.</param>
/// <param name="expressionTree">The expression tree.</param>
/// <returns>True if it changed the expression tree.</returns>
protected virtual bool CompileUnaryOperators(EvaluationContext context, IList <ProcessedItem> expressionTree) =>
TreeLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (expressionTree.Count > i + 1 &&
item.ItemType == typeof(EUnaryOperator) &&
expressionTree[i + 1].Expression != null)
{
Expression expr = expressionTree[i + 1].Expression;
expr =
Expression.MakeUnary(context.UnaryNodeTypes[item.Content],
expr,
expr.Type
);
ProcessedItem newItem = ProcessedItem.Create(expr);
expressionTree.RemoveAt(i);
expressionTree.RemoveAt(i);
expressionTree.Insert(i, newItem);
return(true);
}
return(false);
});
/// <summary>
/// Compile the expression tree produced by parser.
/// </summary>
/// <param name="context">The context of evaluation.</param>
/// <param name="expressionTree">The expression tree.</param>
/// <returns>Result expression.</returns>
protected virtual Expression Compile(EvaluationContext context, IList <ProcessedItem> expressionTree)
{
// move brackets into subtrees
TreeLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (item.ItemType == typeof(ExpressionBlock))
{
int num = 1;
int j = i + 1;
while (num > 0 && j < expressionTree.Count)
{
ProcessedItem itemToMove = expressionTree[j];
if (itemToMove.ItemType == typeof(EExpressionEnd))
{
num--;
}
else if (itemToMove.ItemType == typeof(ExpressionBlock))
{
num++;
}
if (itemToMove.ItemType != typeof(EExpressionEnd) || num > 0)
{
item.Items.Add(itemToMove);
}
expressionTree.RemoveAt(j);
}
if (num > 0)
{
throw new EvaluationException("Expected ')' at the end of the expression.");
}
return(true);
}
return(false);
});
// compile subtrees
ReverseLoop(expressionTree, i =>
{
ProcessedItem item = expressionTree[i];
if (item.ItemType == typeof(ExpressionBlock))
{
Expression expr = Compile(context, item.Items);
ProcessedItem newItem = ProcessedItem.Create(expr);
expressionTree.RemoveAt(i);
expressionTree.Insert(i, newItem);
return(true);
}
return(false);
});
bool changed;
do
{
changed = false;
changed |= ReverseLoop(expressionTree, i =>
{
ProcessedItem item1 = expressionTree[i];
if (item1.ItemType != typeof(ETypeCast) || item1.TypeToCast == null)
{
return(false);
}
if (i + 1 >= expressionTree.Count)
{
return(false);
}
ProcessedItem item2 = expressionTree[i + 1];
if (item2 is ProcessedItem)
{
Expression expr = Expression.Convert(item2.Expression, item1.TypeToCast);
ProcessedItem newItem = ProcessedItem.Create(expr);
expressionTree.RemoveAt(i);
expressionTree.RemoveAt(i);
expressionTree.Insert(i, newItem);
return(true);
}
return(false);
});
changed |= CompileSingleItem(context, expressionTree);
changed |= CompileMemberAccess(expressionTree);
changed |= CompileUnaryOperators(context, expressionTree);
changed |= CompileBinaryOperators(context, expressionTree);
changed |= CompileIIfOperators(context, expressionTree);
if (expressionTree.Count == 1 && expressionTree[0].Expression != null)
{
return(expressionTree[0].Expression);
}
if (expressionTree.Count == 1 && expressionTree[0].TypeToCast != null)
{
return(null);
}
} while (changed);
throw new EvaluationException($"Expression compilation failed.\n{string.Join("\n", expressionTree.Select(o => o.Content).ToArray())}");
}