public int Parse(List <Token> tokens)
{
bool hasLHV = false;
BinaryOperation operation = new BinaryOperation();
for (var i = 0; i < tokens.Count; i++)
{
var token = tokens[i];
switch (token.MyType)
{
case Token.Type.Plus:
operation.Operation = BinaryOperation.OperationType.Addition;
break;
case Token.Type.Minus:
operation.Operation = BinaryOperation.OperationType.Subtraction;
break;
case Token.Type.Integer:
if (tokens.Count == 1)
{
return(Int32.Parse(token.Text));
}
var val = new Integer(Int32.Parse(token.Text));
if (!hasLHV)
{
operation.LeftVal = val;
hasLHV = true;
}
else
{
operation.RightVal = val;
var newToken = new Token(Token.Type.Integer, operation.Value.ToString());
var newTokenList = new List <Token> {
newToken
};
newTokenList.AddRange(tokens.Skip(i + 1));
return(Parse(newTokenList));
}
break;
case Token.Type.String:
if (token.Text.Length > 1 || !Variables.ContainsKey(token.Text[0]))
{
return(0);
}
var charVal = new Integer(Variables[token.Text[0]]);
if (!hasLHV)
{
operation.LeftVal = charVal;
hasLHV = true;
}
else
{
operation.RightVal = charVal;
var newToken = new Token(Token.Type.Integer, operation.Value.ToString());
var newTokenList = new List <Token> {
newToken
};
newTokenList.AddRange(tokens.Skip(i + 1));
return(Parse(newTokenList));
}
break;
default:
throw new ArgumentOutOfRangeException();
}
}
return(0);
}
private IElement Parse(IReadOnlyList <Token> tokens)
{
var result = new BinaryOperation();
var opDefined = false;
bool IsFinalOperand(int index, Token token, IElement element)
{
if (result.Left == null && !opDefined)
{
result.Left = element;
}
else if (!opDefined)
{
throw new ExceptionParseError($"Incorrect token: {token}");
}
else
{
result.Right = element;
}
return(index == tokens.Count - 1);
}
void ResetResult()
{
var r0 = new BinaryOperation()
{
Left = result, Right = null
};
result = r0;
opDefined = false;
}
for (int i = 0; i < tokens.Count; i++)
{
var token = tokens[i];
switch (token.TokenType)
{
case Token.Type.IntConst:
var c = new Integer(int.Parse(token.Text));
if (!IsFinalOperand(i, token, c) && opDefined)
{
ResetResult();
}
break;
case Token.Type.IntVar:
var v = new IntVar(token.Text[0], this);
if (!IsFinalOperand(i, token, v) && opDefined)
{
ResetResult();
}
break;
case Token.Type.Plus:
opDefined = true;
result.OperationType = BinaryOperation.Type.Addition;
break;
case Token.Type.Minus:
opDefined = true;
result.OperationType = BinaryOperation.Type.Subtraction;
break;
default:
throw new ArgumentOutOfRangeException();
}
}
return(opDefined ? result : result.Left);
}