1 \documentclass{article}

     2 \usepackage{../style}

     3 \usepackage{../langs}

     4 \usepackage{marvosym}

     5 \usepackage{tcolorbox}

     6 %% \usepackage[]{hvextern}

     7 

     8 %cheat sheet

     9 %http://worldline.github.io/scala-cheatsheet/

    10 

    11 \begin{document}

    12 \fnote{\copyright{} Christian Urban, King's College London, 2025}

    13 

    14 \section*{Ammonite ``Quirks''}

    15 

    16 While Ammonite is great when it comes to additional features, such as

    17 multiple main's and dynamically loading files, and in the past it was

    18 a rock-solid piece of software written by one of my Scala-heroes

    19 (Haoyi Li), it seems it has acquired some ``quirks'' when it

    20 transitioned to Scala 3. Interestingly, the problems listed below only occur

    21 inside the REPL. So running Scala-scripts on the command

    22 line with for example

    23 

    24 \begin{lstlisting}[language={},numbers=none,basicstyle=\ttfamily\small]

    25 $ amm cw02.sc

    26 \end{lstlisting} %% $

    27 

    28 \noindent

    29 works fine. Similarly, the original Scala REPL seems to not suffer 

    30 from these quirks. Unfortunately, this REPL does not allow you to

    31 dynamically load files which might be relevant in later CWs.

    32 

    33 \subsection*{Problem with Implicits}

    34 

    35 In CW2 (and possibly others), if you use the template code and develop

    36 your code inside the REPL, a problem arises in the line

    37 

    38 \begin{lstlisting}[numbers=none,language=Scala]

    39 val KEYWORD : Rexp = "while" | "if" | "then" 

    40 \end{lstlisting}

    41 

    42 \noindent with the error

    43 

    44 \begin{lstlisting}[numbers=none,language=Scala]

    45 -- [E008] Not Found Error: cmd17.sc:1:36 -----------------------------

    46 1 |val KEYWORD : Rexp = "while" | "if" | "then" 

    47   |                     ^^^^^^^^^^^^^^^^

    48   |value | is not a member of ammonite.$sess.cmd4.ALT.

    49   |An extension method was tried, but could not be fully constructed:

    50   |

    51   |    ammonite.$sess.cmd16.|()

    52   |

    53   |    failed with:

    54   |

    55   |        value |: <overloaded ammonite.$sess.cmd16.|> does not take 

    56   |        parameters

    57   |Compilation Failed

    58 \end{lstlisting}%$\medskip

    59 

    60 

    61 \noindent\textbf{Fix:} The code runs absolutely fine when called on the

    62 commandline. It also runs absolutely fine inside the standard Scala REPL.

    63 If you prefer to use to use the Ammonite REPL, then you need to make the 

    64 following changes: (1) comment out the implicits below and change the 

    65 \code{$} to for example \code{&}%$:

    66 

    67 \begin{lstlisting}[numbers=none,language=Scala]

    68 extension (s: String) {

    69   def & (r: Rexp) = RECD(s, r)

    70   //def | (r: Rexp) = ALT(s, r)

    71   //def | (r: String) = ALT(s, r)

    72   //def % = STAR(s)

    73   //def ~ (r: Rexp) = SEQ(s, r)

    74   //def ~ (r: String) = SEQ(s, r)

    75 }

    76 \end{lstlisting}

    77 

    78 \noindent You need to then use \code{&} in the code for the 

    79 \code{WHILE_REGS}

    80 

    81 \end{document}

    82 

    83 %%% Local Variables: 

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    85 %%% TeX-master: t

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