/// <summary>
/// Checks need of adding nil element to transform -x to 0-x.
/// </summary>
/// <param name="currentChar"></param>
internal void CheckAndAddNilElement(char currentChar)
{
if (VariableBuilder.Length != 0 || currentChar == '=')
{
return;
}
// apply imitation only on formula start or after equal operator
if (ExpressionsStack.Count == 0 || OperatorsStack.Count > 0 && OperatorsStack.Peek() == '=')
{
// 0 imitation in start or after '=': -x => 0-x +x => 0+x
ExpressionsStack.Push(new VariableExpressionsGroup(new VariablesExpression()));
}
}
/// <summary>
/// Push variable from <see cref="VariableBuilder"/> to <see cref="ExpressionsStack"/>.
/// </summary>
internal void PushVariable()
{
if (VariableBuilder.Length <= 0)
{
return;
}
var variablevalue = VariableBuilder.ToString();
var variable = _expressionFactory.GetVariable(variablevalue);
if (variable == null)
{
throw new InvalidFormulaException(_formula, $"cannot parse variable '{variablevalue}'");
}
ExpressionsStack.Push(new VariableExpressionsGroup(variable));
VariableBuilder.Clear();
}
/// <summary>
/// Apply operator from <see cref="OperatorsStack"/>.
/// </summary>
internal void ApplyTopOperator()
{
if (OperatorsStack.Count == 0)
{
return;
}
var operatorChar = OperatorsStack.Pop();
if (operatorChar == '(')
{
throw new InvalidFormulaException(_formula, "all parentheses must be closed");
}
PushVariable();
if (ExpressionsStack.Count < 2)
{
throw new InvalidFormulaException(_formula, $"not enough operands to apply {operatorChar} operator");
}
var rightOperand = ExpressionsStack.Pop();
ExpressionsStack.Peek().Combine(rightOperand, changeSign: operatorChar != '+');
}
