Example 6.11.1, p. 67 of ScalaReference.pdf, aka circa l. 3325 of ~scala-documentation/trunk/src/reference/ReferencePart.tex
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\example The following method returns the $n$'th column of a given
list of row-lists $xss$, using methods \lstinline@map@,
\lstinline@drop@ and \lstinline@head@ defined in class
\lstinline@scala.List@.
\begin{lstlisting}
def column[T](xss: List[List[T]], n: int): List[T] = 
  xss.map(.drop(i)).map(.head)
\end{lstlisting}
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Compiling the example :

scalatest.scala:22 error: not found: value i
  xss.map(.drop(i)).map(.head)
                ^
one error found