unquote.cs

        private static IEnumerable<Expression> Unquote(Expression expression, SymbolTable symbols, Int32 level)
        {
            return (expression as ListExpression).Null(el => el[0].Id().Let(i => i == "quasiquote"
                ? Unquote(el[1], symbols, ++level)
                : i == "unquote"
                      ? EnumerableEx.Generate(
                            el,
                            _ => _ != null && _[0].Id() == "unquote",
                            _ => _[1] as ListExpression,
                            _ => _[1]
                        )
                            .ToArray()
                            .Let(es => Enumerable.Range(0, level - es.Length)
                                .Aggregate(es.Last(), (e_, _) => Quote(symbols, e_))
                            )
                            .If(_ => _ is IdentifierExpression && !(((IdentifierExpression) _).Reduce(symbols).Type == typeof(IdentifierExpression)), _ => Function(symbols, "const", _))
							.Let(EnumerableEx.Return)
                      : i == "unquote-splicing"
                            ? Enumerable.Range(0, 10).Select(x => Constant(x))
                            : EnumerableEx.Return<Expression>(Function(symbols, "list", el.Elements.SelectMany(e => Unquote(e, symbols, level))))
            )) ?? EnumerableEx.Return(
                (expression as VectorExpression).Null(ev => Vector(symbols, ev.Elements.SelectMany(e => Unquote(e, symbols, level)))) ??
                (expression as LambdaListExpression).Null(el => LambdaList(symbols, el.Elements.SelectMany(e => Unquote(e, symbols, level)))) ??
                (Expression) Quote(symbols, expression)
            );