Lucene.Net.QueryParsers.QueryParser.AddClause C# (CSharp) Method

        protected internal virtual void AddClause(List<BooleanClause> clauses, int conj, int mods, Query q)
        {
            bool required, prohibited;

            // If this term is introduced by AND, make the preceding term required,
            // unless it's already prohibited
            if (clauses.Count > 0 && conj == CONJ_AND)
            {
                BooleanClause c = clauses[clauses.Count - 1];
                if (!c.IsProhibited)
                    c.Occur = Occur.MUST;
            }

            if (clauses.Count > 0 && operator_Renamed == AND_OPERATOR && conj == CONJ_OR)
            {
                // If this term is introduced by OR, make the preceding term optional,
                // unless it's prohibited (that means we leave -a OR b but +a OR b-->a OR b)
                // notice if the input is a OR b, first term is parsed as required; without
                // this modification a OR b would parsed as +a OR b
                BooleanClause c = clauses[clauses.Count - 1];
                if (!c.IsProhibited)
                    c.Occur = Occur.SHOULD;
            }

            // We might have been passed a null query; the term might have been
            // filtered away by the analyzer.
            if (q == null)
                return;

            if (operator_Renamed == OR_OPERATOR)
            {
                // We set REQUIRED if we're introduced by AND or +; PROHIBITED if
                // introduced by NOT or -; make sure not to set both.
                prohibited = (mods == MOD_NOT);
                required = (mods == MOD_REQ);
                if (conj == CONJ_AND && !prohibited)
                {
                    required = true;
                }
            }
            else
            {
                // We set PROHIBITED if we're introduced by NOT or -; We set REQUIRED
                // if not PROHIBITED and not introduced by OR
                prohibited = (mods == MOD_NOT);
                required = (!prohibited && conj != CONJ_OR);
            }
            if (required && !prohibited)
                clauses.Add(NewBooleanClause(q, Occur.MUST));
            else if (!required && !prohibited)
                clauses.Add(NewBooleanClause(q, Occur.SHOULD));
            else if (!required && prohibited)
                clauses.Add(NewBooleanClause(q, Occur.MUST_NOT));
            else
                throw new SystemException("Clause cannot be both required and prohibited");
        }