private void TryParseBindAssignment(SparqlQueryParserContext context, GraphPattern p)
{
if (context.SyntaxMode == SparqlQuerySyntax.Sparql_1_0) throw new RdfParseException("BIND assignment is not supported in SPARQL 1.0");
//First need to discard opening (
IToken next = context.Tokens.Dequeue();
if (next.TokenType != Token.LEFTBRACKET) throw ParserHelper.Error("Unexpected Token '" + next.GetType().ToString() + "' encountered, expected a ( to start a BIND assignment after a BIND keyword", next);
//Expect a bracketted expression terminated by an AS
ISparqlExpression expr = this.TryParseExpression(context, false, true);
if (context.Tokens.LastTokenType != Token.AS)
{
throw ParserHelper.Error("A BIND assignment did not end with an AS ?var as expected, BIND assignment must be of the general form BIND(expr AS ?var)", next);
}
//Ensure there is a Variable after the AS
next = context.Tokens.Dequeue();
if (next.TokenType == Token.VARIABLE)
{
BindPattern bind = new BindPattern(next.Value.Substring(1), expr);
//Check that the Variable has not already been used
if (context.Query.RootGraphPattern != null && context.Query.RootGraphPattern.Variables.Contains(bind.VariableName))
{
throw ParserHelper.Error("A BIND assignment is attempting to bind to the variable ?" + bind.VariableName + " but this variable is already in use in the query", next);
}
else if (p.Variables.Contains(bind.VariableName))
{
throw ParserHelper.Error("A BIND assignment is attempting to bind to the variable ?" + bind.VariableName + " but this variable is already in use earlier in the Graph pattern", next);
}
if (Options.QueryOptimisation)
{
p.AddAssignment(bind);
}
else
{
//When Optimisation is turned off we'll just stick the BIND in the Triples Pattern where it occurs
//since we're not going to do any Triple Pattern ordering, Assignment or FILTER placement
p.AddTriplePattern(bind);
//In this case the BIND must break the BGP since using AddTriplePattern will not do it automatically
p.BreakBGP();
}
//Ensure the BIND assignment is terminated with a )
next = context.Tokens.Dequeue();
if (next.TokenType != Token.RIGHTBRACKET) throw ParserHelper.Error("Unexpected Token '" + next.GetType().ToString() + "' encountered, expected a ) to terminate a BIND assignment", next);
}
else
{
throw ParserHelper.Error("Unexpected Token '" + next.GetType().ToString() + "' encountered, expected a Variable after the AS in a BIND assignment", next);
}
}
