public decimal Solve(Equation equation)
{
decimal left = 0m;
decimal right = 0m;
for (var i = 0; i < equation.Tokens.Count; i++)
{
var token = equation.Tokens[i];
if (i == 0 && token.Type == TokenType.Value)
{
left = (decimal)token.Value;
continue;
}
if (token.Type == TokenType.Operator)
{
var rightToken = equation.Tokens[++i];
if (rightToken.Type == TokenType.Value)
{
right = (decimal)rightToken.Value;
}
left = Solve(left, right, token.Value.ToString());
}
}
return left;
}
public Equation Parse(string value)
{
var equation = new Equation()
{
Tokens = new List<Token>()
};
if (value == null)
return equation;
var current = "";
var currentType = TokenType.None;
Token currentToken = null;
for (int i = 0; i < value.Length; i++)
{
var item = value[i];
var type = GetTokenType(item);
if (type != currentType)
{
// add
if (currentToken != null)
{
if (currentToken.Type == TokenType.Value)
{
currentToken.Value = decimal.Parse(current);
}
else
{
currentToken.Value = current;
}
equation.Tokens.Add(currentToken);
}
currentToken = new Token();
currentToken.Type = type;
current = item.ToString();
}
else
{
current += item;
}
}
if (currentToken != null)
{
if (currentToken.Type == TokenType.Value)
{
currentToken.Value = decimal.Parse(current);
}
else
{
currentToken.Value = current;
}
equation.Tokens.Add(currentToken);
}
return equation;
}
public void WhenExecutingAndAddEquation_ThenResultShouldEqualThree()
{
// Arrange
var calculator = new Calculator();
var equation = new Equation()
{
Tokens = new List<Token>()
{
new Token() {Value = 1m, Type = TokenType.Value},
new Token() {Value = "+", Type = TokenType.Operator},
new Token() {Value = 2m, Type = TokenType.Value},
}
};
// Act
var result = calculator.Solve(equation);
// Assert
Assert.AreEqual(3m, result);
}