public string Print(IASTNode tree)
{
if (tree == null)
{
throw new ArgumentNullException("tree", "The argument cannot equal to null");
}
return(tree.Accept(this));
}
public Object VisitIfThenElseNode(IIfThenElseASTNode ifStatementNode)
{
if (ifStatementNode == null)
{
throw new ArgumentNullException("ifStatementNode", "The argument cannot equal to null");
}
if (ifStatementNode.Variable == null)
{
throw new ArgumentNullException("ifStatementNode.Variable", "The argument cannot equal to null");
}
if (ifStatementNode.Predicate == null)
{
throw new ArgumentNullException("ifStatementNode.Predicate", "The argument cannot equal to null");
}
Func <int, bool> predicate = (Func <int, bool>)(ifStatementNode.Predicate as IASTNode).Accept(this);
int[] evaluatedExpr = null;
IASTNode variableNode = ifStatementNode.Variable;
if ((variableNode.Type == E_NODE_TYPE.NT_IDENTIFIER) &&
((variableNode.Attributes & E_NODE_ATTRIBUTES.NA_LVALUE) == E_NODE_ATTRIBUTES.NA_LVALUE))
{
evaluatedExpr = mEnvironment.Get((string)(variableNode).Accept(this)); // variable is lvalue
}
else
{
evaluatedExpr = (int[])variableNode.Accept(this); // variable is rvalue, replace it with its value
}
bool conditionResult = evaluatedExpr.Length >= 1 ? predicate(evaluatedExpr[0]) : false;
if (conditionResult)
{
if (ifStatementNode.ThenBranch == null)
{
throw new ArgumentNullException("ifStatementNode.ThenBranch", "The argument cannot equal to null");
}
return(ifStatementNode.ThenBranch.Accept(this));
}
if (ifStatementNode.ElseBranch == null)
{
throw new ArgumentNullException("ifStatementNode.ElseBranch", "The argument cannot equal to null");
}
return(ifStatementNode.ElseBranch.Accept(this));
}
/// <summary>
/// The method evaluates (executes) a program, which is represented as a syntax tree of nodes.
/// An input parameters could be integer arrays or integer values (represented as an array with single value).
/// </summary>
/// <param name="program">A program is represented as an AST</param>
/// <param name="inputStream">Program's input data</param>
/// <returns>An evaluated array of some data</returns>
public int[] Eval(IASTNode program, IInputStream inputStream)
{
if (program == null)
{
throw new ArgumentNullException("program", "The argument cannot equal to null");
}
if (inputStream == null)
{
throw new ArgumentNullException("inputData", "The argument cannot equal to null");
}
mInputStream = inputStream;
mEnvironment.Clear();
return((int[])program.Accept(this));
}
