public void SumTest()
{
var visitor = new DumpVisitor();
var parser = new Parser();
string data = "1+2";
var expr = parser.Parse(data);
expr.Accept(visitor);
Assert.AreEqual("BinaryExpr(Literal(1)+Literal(2))", visitor.ToString());
}
public void JustVarTest()
{
var visitor = new DumpVisitor();
var parser = new Parser();
string data = "a";
var expr = parser.Parse(data);
expr.Accept(visitor);
Assert.AreEqual("Variable(a)", visitor.ToString());
}
public void MoreParenTest()
{
var visitor = new DumpVisitor();
var parser = new Parser();
string data = "(a-(3))";
var expr = parser.Parse(data);
expr.Accept(visitor);
Assert.AreEqual("ParenExpr(BinaryExpr(Variable(a)-ParenExpr(Literal(3))))", visitor.ToString());
}
public void OpsTest()
{
var visitor = new DumpVisitor();
var parser = new Parser();
string data = "1+a*3-b/5";
var expr = parser.Parse(data);
expr.Accept(visitor);
Assert.AreEqual("BinaryExpr(BinaryExpr(Literal(1)+BinaryExpr(Variable(a)*Literal(3)))-BinaryExpr(Variable(b)/Literal(5)))", visitor.ToString());
}
public static IExpression Parse(string text)
{
var dumpVisitor = new DumpVisitor();
Stack <IExpression> variableAndLetter = new Stack <IExpression>();
Stack <char> operators = new Stack <char>();
for (var i = 0; i < text.Length; i++)
{
var ch = text[i];
if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
{
if (operators.Count == 0)
{
operators.Push(ch);
}
else if (isCurrentOpLessPriority(ch, operators.Peek()))
{
var highPriorOper = operators.Pop();
operators.Push(ch);
var secondEl = variableAndLetter.Pop();
var firstEl = variableAndLetter.Pop();
variableAndLetter.Push(new BinaryExpression(firstEl, secondEl, highPriorOper.ToString()));
}
else
{
operators.Push(ch);
}
}
else if (ch == '(')
{
operators.Push(ch);
}
else if (ch == ')')
{
while (operators.Peek() != '(')
{
if (operators.Count == 0)
{
throw new FormatException("Incorrect expression");
}
char op = operators.Pop();
var secondEl = variableAndLetter.Pop();
var firstEl = variableAndLetter.Pop();
variableAndLetter.Push(new BinaryExpression(firstEl, secondEl, op.ToString()));
}
operators.Pop();
}
else if (char.IsDigit(ch))
{
variableAndLetter.Push(new Literal(ch.ToString()));
}
else if (char.IsLetter(ch))
{
variableAndLetter.Push(new Variable(ch.ToString()));
}
else
{
throw new FormatException("Incorrect element in expression");
}
}
while (variableAndLetter.Count > 1)
{
char oper = operators.Pop();
var second = variableAndLetter.Pop();
var first = variableAndLetter.Pop();
variableAndLetter.Push(new BinaryExpression(first, second, oper.ToString()));
}
return(variableAndLetter.Pop());
}
