Edit to L21 based on suggestion from Emil Sekerinski

Lectures/L21_IntroToSpecification/IntroToSpecification.tex

@@ -224,7 +224,9 @@
 \item \structure<1>{What does this notation mean?}
 \item \uncover<2->{\structure<2>{$1+1+1 = 3$}}
 \item \uncover<3->{\structure<3>{How would we say this in Python?}}
-\item \uncover<4->{\structure<4>{\texttt{reduce(lambda x, y: x+y, [1 for x in range(6) if x\%2==0], 0)}}}
+\item \uncover<4->{\structure<4>{\texttt{sum(x \% 2 == 0 for x in range(6))}, or}}
+\item \uncover<5->{\structure<5>{\texttt{reduce(lambda x, y: x+y, [1 for x in
+        range(6) if x\%2==0], 0)}}}
 \ei
 
 \end{frame}