private decimal Reduce(string expression, char operation, Func<string, decimal> furtherReduction)
{
var tokens = expression.Split(operation);
Operand operand = furtherReduction(tokens[0]);
for (int i = 1; i < tokens.Length; i++) {
operand = new Operand(operand, furtherReduction(tokens[i]), operation);
}
return operand;
}
public Operand(Operand firstOperand, Operand secondOperand, char operation)
{
Value = secondOperand == null
? firstOperand.Value
: _operationDefinitions[operation](firstOperand, secondOperand);
}
