System.Xml.Xsl.IlGen.XmlILOptimizerVisitor.FoldComparison C# (CSharp) Method

        private QilNode FoldComparison(QilNodeType opType, QilNode left, QilNode right) {
            object litLeft, litRight;
            int cmp;
            Debug.Assert(left.XmlType == right.XmlType, "Comparison is not defined between " + left.XmlType + " and " + right.XmlType);

            // Extract objects that represent each literal value
            litLeft = ExtractLiteralValue(left);
            litRight = ExtractLiteralValue(right);

            if (left.NodeType == QilNodeType.LiteralDouble) {
                // Equals and CompareTo do not handle NaN correctly
                if (Double.IsNaN((double) litLeft) || Double.IsNaN((double) litRight))
                    return (opType == QilNodeType.Ne) ? f.True() : f.False();
            }

            if (opType == QilNodeType.Eq)
                return litLeft.Equals(litRight) ? f.True() : f.False();

            if (opType == QilNodeType.Ne)
                return litLeft.Equals(litRight) ? f.False() : f.True();

            if (left.NodeType == QilNodeType.LiteralString) {
                // CompareTo does not use Ordinal comparison
                cmp = string.CompareOrdinal((string) litLeft, (string) litRight);
            }
            else {
                cmp = ((IComparable) litLeft).CompareTo(litRight);
            }

            switch (opType) {
                case QilNodeType.Gt: return cmp > 0 ? f.True() : f.False();
                case QilNodeType.Ge: return cmp >= 0 ? f.True() : f.False();
                case QilNodeType.Lt: return cmp < 0 ? f.True() : f.False();
                case QilNodeType.Le: return cmp <= 0 ? f.True() : f.False();
            }

            Debug.Assert(false, "Cannot fold this comparison operation: " + opType);
            return null;
        }