ExpressionizeResult CreateExpression(int basePrecedence)
{
Expression single = null;
// Make an atom.
ExpressionizeResult atomResult = CreateAtom();
if (!atomResult.Success)
{
return(atomResult);
}
// Atomizing succeeded.
single = atomResult.CalculatedExpression;
while (true)
{
// After an atom might be an operator, an argument or another expression.
// End of the token list.
if (currentToken == null)
{
break;
}
// Operator after an atom.
if (TokenType.Operator.HasFlag(currentToken.Type))
{
BinaryType binaryType = currentToken.Type.ToBinaryType();
int opPrecedence = binaryType.GetPrecedence();
if (opPrecedence < basePrecedence)
{
break;
}
int nextPrecedence = binaryType.IsLeftAssociative() ? (opPrecedence + 1) : opPrecedence;
GetNextToken();
ExpressionizeResult rightResult = CreateExpression(nextPrecedence);
if (!rightResult.Success)
{
return(rightResult);
}
Expression left = single;
Expression right = rightResult.CalculatedExpression;
single = new BinaryExpression(left, right, binaryType);
}
else
{
// Variable or left parenthesis after an atom,
// connect them with implied multiplication.
if (currentToken.Type == TokenType.Variable || currentToken.Type == TokenType.ParenLeft)
{
BinaryType binaryType = BinaryType.ImpliedMultiply;
int opPrecedence = binaryType.GetPrecedence();
if (opPrecedence < basePrecedence)
{
break;
}
int nextPrecedence = binaryType.IsLeftAssociative() ? (opPrecedence + 1) : opPrecedence;
// No need to consume the operator token.
ExpressionizeResult rightResult = CreateExpression(nextPrecedence);
if (!rightResult.Success)
{
return(rightResult);
}
Expression right = rightResult.CalculatedExpression;
single = new BinaryExpression(single, right, binaryType);
}
else
{
if (currentToken.Type == TokenType.Constant)
{
return(ExpressionizeResult.NewError(ErrorInfo.ExpectOperator));
}
// The current expression ends if we encounter anything else.
break;
}
}
}
return(ExpressionizeResult.NewSuccess(single));
}
