/// <summary>
/// Returns a relational expression from 2 operands and the operator (with appropriate error handling).
/// </summary>
public static Expression Build(IList <Expression> operands, string relationalOperator)
{
if (operands.Count == 1)
{
return(operands[0]);
}
if (operands.Count != 2)
{
return(null);
}
ExpressionOperand parameterAsExpression = operands[0] as ExpressionOperand;
ExpressionOperand equivalenceClassAsExpression = operands[1] as ExpressionOperand;
if ((parameterAsExpression == null) ||
(equivalenceClassAsExpression == null))
{
return(null);
}
return(new ExpressionRelational
{
ParameterName = parameterAsExpression.Operands[0],
EquivalenceClassNames = equivalenceClassAsExpression.Operands,
RelationalOperator = relationalOperator
});
}
/// <summary>
/// Parses and returns the operand (or parenthesized expression) as an expression.
/// </summary>
private static Expression ParseOperand(IList <string> expressionTokens, ref int index)
{
string token = Token(expressionTokens, index, false);
if (token == ParenthesisLeft)
{
index++;
Expression expression = ParseOr(expressionTokens, ref index);
if ((expression == null) || (Token(expressionTokens, index, false) != ParenthesisRight))
{
return(null);
}
index++;
return(expression);
}
if (token == BracketLeft)
{
index++;
IList <string> alternatives = new List <string>();
string alternative = Token(expressionTokens, index, false);
while (alternative != BracketRight)
{
alternatives.Add(alternative);
index++;
alternative = Token(expressionTokens, index, false);
if (alternative == Comma)
{
index++;
alternative = Token(expressionTokens, index, false);
}
}
index++;
return(ExpressionOperand.Build(alternatives));
}
index++;
return(ExpressionOperand.Build(token));
}