diff --git a/1.4-scheme_lists.tex b/1.4-scheme_lists.tex
index ab50a8a..dcf5bbe 100644
--- a/1.4-scheme_lists.tex
+++ b/1.4-scheme_lists.tex
@@ -1,6 +1,16 @@
 \documentclass[alsotrans,beameroptions={aspectratio=169}]{beamerswitch}
 \usepackage{fprog}
 
+\ExplSyntaxOn
+\cs_set:Npn \tbl_crcr:n #1 {
+     \int_compare:nNnT \g__tbl_col_int > 0
+         {
+           \tbl_count_missing_cells:n {#1}
+         }
+     \crcr
+   }
+\ExplSyntaxOff
+
 \title{Списъци}
 
 \date{16--23 октомври 2024 г.}
@@ -473,33 +483,33 @@ \section{Функции от по-висок ред за списъци}
   В Racket са дефинирани функциите \tt{map}, \tt{filter}, \tt{foldr}, \tt{foldl}\\[2ex]
   \pause
   \alert{Внимание: \tt{foldl} в Racket е дефинирана по различен начин!}\\[2ex]
-  \begin{columns}[T,onlytextwidth]
-    \small
-    \begin{column}{.5\textwidth}
-      \tt{foldl} от лекции\\[2ex]
-\begin{lstlisting}
-(define (foldl op nv l)
-  (if (null? l) nv
-      (foldl op @\alert{(op nv (car l))}@
-             (cdr l))))
-\end{lstlisting}
-      \begin{equation*}
-        \Big(\ldots\big((\bot \oplus a_1) \oplus a_2\big) \oplus \ldots\Big) \oplus a_n
-      \end{equation*}
-    \end{column}
-    \begin{column}{.5\textwidth}
-      \tt{foldl} в Racket\\[2ex]
-\begin{lstlisting}
-(define (foldl op nv l)
-  (if (null? l) nv
-      (foldl op @\alert{(op (car l) nv)}@
-             (cdr l))))
-\end{lstlisting}
-      \begin{equation*}
-        a_n \oplus \Big(\ldots \big(a_2 \oplus (a_1 \oplus \bot)\big)\ldots\Big),
-      \end{equation*}
-    \end{column}
-  \end{columns}
+%   \begin{columns}[T,onlytextwidth]
+%     \small
+%     \begin{column}{.5\textwidth}
+%       \tt{foldl} от лекции\\[2ex]
+% \begin{lstlisting}
+% (define (foldl op nv l)
+%   (if (null? l) nv
+%       (foldl op @\alert{(op nv (car l))}@
+%              (cdr l))))
+% \end{lstlisting}
+%       \begin{equation*}
+%         \Big(\ldots\big((\bot \oplus a_1) \oplus a_2\big) \oplus \ldots\Big) \oplus a_n
+%       \end{equation*}
+%     \end{column}
+%     \begin{column}{.5\textwidth}
+%       \tt{foldl} в Racket\\[2ex]
+% \begin{lstlisting}
+% (define (foldl op nv l)
+%   (if (null? l) nv
+%       (foldl op @\alert{(op (car l) nv)}@
+%              (cdr l))))
+% \end{lstlisting}
+%       \begin{equation*}
+%         a_n \oplus \Big(\ldots \big(a_2 \oplus (a_1 \oplus \bot)\big)\ldots\Big),
+%       \end{equation*}
+%     \end{column}
+%   \end{columns}
 \end{frame}
 
 \begin{frame}[fragile]
@@ -526,7 +536,7 @@ \section{Функции от по-висок ред за списъци}
 \begin{lstlisting}
 (define (foldl1 op l)
   (foldl op (car l) (cdr l)))
-\end{lstlisting}
+\end{lstlisting}\\
   \end{tabular}
 \end{frame}