/// <summary>
/// Evaluates a TokenCollection representing a mathematical
/// expression and returns the result.
/// </summary>
/// <param name="tokens">The TokenCollection to be evaluated.</param>
/// <returns>The result of the expression.</returns>
public decimal Evaluate(TokenCollection tokens)
{
var values = new Stack <decimal>();
try
{
foreach (Token token in tokens.AsPostfix())
{
decimal result;
switch (token)
{
case ValueToken value:
result = value.Evaluate();
break;
case UnaryOperatorToken unaryOp:
result = unaryOp.Evaluate(values.Pop());
break;
case BinaryOperatorToken binaryOp:
decimal rightValue = values.Pop();
decimal leftValue = values.Pop();
result = binaryOp.Evaluate(leftValue, rightValue);
break;
default:
throw new InvalidExpressionException($"Token '{token}' cannot be evaluated");
}
values.Push(result);
}
return(values.Pop());
}
catch (InvalidOperationException ex)
{
throw new InvalidExpressionException(ex);
}
}