pep-material: comparison handouts/pep-ho.tex

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 %https://www.metalevel.at/prolog/optimization
 % nice example for map and reduce using Harry potter characters
 % https://www.matthewgerstman.com/map-filter-reduce/
+% interesting talk about differences in Java and Scala
+% Goto'19 conference ; about differences in type-system
+% https://www.youtube.com/watch?v=e6n-Ci8V2CM
 % Timing
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 % xs.map(x => (x, xs.count(_==x)))
 %
 \subsection*{Why Functional Programming?}
 Before we go on, let me explain a bit more why we want to inflict upon
 you another programming language. You hopefully have mastered Java and
-C++\ldots{}the world should be your oyster, no? Well, this is not as
+C++\ldots{}the world should be your oyster, no? Well, matters are not as
-simple as one might wish. We do require Scala in PEP, but actually we
+simple as one might wish. We do require Scala in PEP, but actually we do
-do not religiously care whether you learn Scala---after all it is just
+not religiously care whether you learn Scala---after all it is just a
-a programming language (albeit a nifty one IMHO). What we do care
+programming language (albeit a nifty one IMHO). What we do care about is
-about is that you learn about \textit{functional programming}. Scala
+that you learn about \textit{functional programming}. Scala is just the
-is just the vehicle for that. Still, you need to learn Scala well
+vehicle for that. Still, you need to learn Scala well enough to get good
-enough to get good marks in PEP, but functional programming could
+marks in PEP, but functional programming could perhaps equally be taught
-equally be taught with Haskell, F\#, SML, Ocaml, Kotlin, Clojure,
+with Haskell, F\#, SML, Ocaml, Kotlin, Clojure, Scheme, Elm and many
-Scheme, Elm and many other functional programming languages.
+other functional programming languages.
-%Your
-%friendly lecturer just happens to like Scala
+%Your friendly lecturer just
-%and the Department agreed that it is a good idea to inflict Scala upon
+%happens to like Scala and the Department agreed that it is a good idea
-%you.
+%to inflict Scala upon you.
 Very likely writing programs in a functional programming language is
 quite different from what you are  used to in your study so far. It
 might even be totally alien to you. The reason is that functional
 programming seems to go against the core principles of
 is that this clock-speed has not much increased over the past decade and
 no dramatic increases are predicted for any time soon. So you are a bit
 stuck. This is unlike previous generations of developers who could rely
 upon the fact that approximately every 2 years their code would run
 twice as fast  because the clock-speed of their CPUs got twice as fast.
 Unfortunately this does not happen any more nowadays. To get you out of
 this dreadful situation, CPU producers pile more and more cores into
 CPUs in order to make them more powerful and potentially make software
 faster. The task for you as developer is to take somehow advantage of
 these cores by running as much of your code as possible in parallel on
-as many cores you have available (typically 4 in modern laptops and
+as many cores you have available (typically 4 or more in modern laptops
-sometimes much more on high-end machines). In this situation
+and sometimes much more on high-end machines). In this situation
-\textit{mutable} variables like \texttt{i} above are evil, or at least a
+\textit{mutable} variables like \texttt{i} in the C-code above are evil,
-major nuisance: Because if you want to distribute some of the
+or at least a major nuisance: Because if you want to distribute some of
-loop-iterations over the cores that are currently idle in your system,
+the loop-iterations over several cores that are currently idle in your
-you need to be extremely careful about who can read and overwrite the
+system, you need to be extremely careful about who can read and
-variable \texttt{i}.\footnote{If you are of the mistaken belief that
+overwrite the variable \texttt{i}.\footnote{If you are of the mistaken
-nothing nasty can happen to \texttt{i} inside the \texttt{for}-loop,
+belief that nothing nasty can happen to \texttt{i} inside the
-then you need to go back over the C++ material.} Especially the writing
+\texttt{for}-loop, then you need to go back over the C++ material.}
-operation is critical because you do not want that conflicting writes
+Especially the writing operation is critical because you do not want
-mess about with \texttt{i}. Take my word: an untold amount of misery has
+that conflicting writes mess about with \texttt{i}. Take my word: an
-arisen from this problem. The catch is that if you try to solve this
+untold amount of misery has arisen from this problem. The catch is that
-problem in C/C++ or Java, and be as defensive as possible about reads
+if you try to solve this problem in C/C++ or Java, and be as defensive
-and writes to \texttt{i}, then you need to synchronise access to it. The
+as possible about reads and writes to \texttt{i}, then you need to
-result is that very often your program waits more than it runs, thereby
+synchronise access to it. The result is that very often your program
-defeating the point of trying to run the program in parallel in the
+waits more than it runs, thereby defeating the point of trying to run
-first place. If you are less defensive, then usually all hell breaks
+the program in parallel in the first place. If you are less defensive,
-loose by seemingly obtaining random results. And forget the idea of
+then usually all hell breaks loose by seemingly obtaining random
-being able to debug such code.
+results. And forget the idea of being able to debug such code.
 The central idea of functional programming is to eliminate any state
 from programs---or at least from the ``interesting bits'' of the
 programs. Because then it is easy to parallelise the resulting
 programs: if you do not have any state, then once created, all memory
 language is lately developing at lightening speed (in comparison to the past)
 taking on many
 features of Scala and other languages, and it seems even it introduces
 new features on its own.
+Scala is deep: After many years, I still continue to learn new technique
+for writing more elegant code.
 %So all in all, Scala might not be a great teaching language,
 %but I hope this is mitigated by the fact that I never require
 %you to write any Scala code. You only need to be able to read
 %it. In the coursework you can use any programming language you
 %like. If you want to use Scala for this, then be my guest; if

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