public static IElement Parse(IReadOnlyList <Token> tokens)
{
var result = new BinaryOperation();
bool haveLHS = false;
for (int i = 0; i < tokens.Count; i++)
{
var token = tokens[i];
// look at the type of token
switch (token.MyType)
{
case Token.Type.Integer:
var integer = new Integer(int.Parse(token.Text));
if (!haveLHS)
{
result.Left = integer;
haveLHS = true;
}
else
{
result.Right = integer;
}
break;
case Token.Type.Plus:
result.MyType = BinaryOperation.Type.Addition;
break;
case Token.Type.Minus:
result.MyType = BinaryOperation.Type.Subtraction;
break;
case Token.Type.Lparen:
int j = i;
for (; j < tokens.Count; ++j)
{
if (tokens[j].MyType == Token.Type.Rparen)
{
break; // found it!
}
}
// process subexpression w/o opening (
var subexpression = tokens.Skip(i + 1).Take(j - i - 1).ToList();
var element = Parse(subexpression);
if (!haveLHS)
{
result.Left = element;
haveLHS = true;
}
else
{
result.Right = element;
}
i = j; // advance
break;
default:
throw new ArgumentOutOfRangeException();
}
}
return(result);
}
public IElement Parse(IReadOnlyList <Token> tokens)
{
var result = new BinaryOperation();
var haveLHS = false;
for (var i = 0; i < tokens.Count; i++)
{
var token = tokens[i];
switch (token.Type)
{
case Type.Integer:
var integer = new Integer(int.Parse(token.Text));
if (!haveLHS)
{
result.LeftElement = integer;
haveLHS = true;
}
else
{
result.RightElement = integer;
}
break;
case Type.Plus:
result.Type = BinaryOperationType.Addition;
break;
case Type.Minus:
result.Type = BinaryOperationType.Subtraction;
break;
case Type.LeftBracket:
int j = i;
for (; j < tokens.Count; ++j)
{
if (tokens[j].Type == Type.RightBracket)
{
break;
}
}
var subexpression = tokens.Skip(i + 1).Take(j - i - 1).ToList();
var element = Parse(subexpression);
if (!haveLHS)
{
result.LeftElement = element;
haveLHS = true;
}
else
{
result.RightElement = element;
}
i = j;
break;
default:
throw new ArgumentOutOfRangeException();
}
}
return(result);
}