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\title{CCSC Haskell tutorial}
\begin{document}

\begin{presentation}
	{CCSC Haskell tutorial}
	{Fritz Ruehr}{1}{6 October 2001}{}

\begin{slide}{Short Haskell applications: text, numbers, treesort and DFAs}
	\slideitem{Simple text processing}
		 \begin{itemize}
		 \item higher-order list functions and a few simple utilities can be combined to do \xlink{../code/short.html#textproc}{simple text processing}
		 \end{itemize}
	\slideitem{ROT-13 transcoder}
		 \begin{itemize}
		 \item similar techniques allow us to define a basic \xlink{../code/short.html#rot13}{"ROT-13" text encryption utility} in about 5 lines
		 \end{itemize}
	\slideitem{Command-line interaction}
		 \begin{itemize}
		 \item Haskell's pre-defined interaction process is based on whole inputs, but a few intervening functions allow us to easily define a \xlink{../code/short.html#rot13}{line-by-line user interaction program}
		 \end{itemize}
	\slideitem{Palindrome checking}
		 \begin{itemize}
		 \item we can check whether a string is a palindrome by normalizing it and comparing it to its own reversal: \xlink{../code/short.html#palcheck}{the palindrome checker}
		 \end{itemize}
	\slideitem{Numeral conversion in different bases}
		 \begin{itemize}
		 \item by spotting certain symmetries in base-radix notation, we can easily write "generator functions" for arbitrary number bases which \xlink{../code/short.html#numbase}{convert between strings and integers}
		 \end{itemize}
	\slideitem{Binary trees and treesort}
		 \begin{itemize}
		 \item a data type for binary search trees, plus an appropriate fold function over those trees, makes \xlink{../code/short.html#treesort}{the definition of tree sort clear and compelling}
		 \end{itemize}
	\slideitem{DFA simulation}
		 \begin{itemize}
		 \item we can transcribe a definition of \xlink{../code/short.html#treesort}{deterministic finite automata} almost verbatim from a theory text, and then experiment with automata and strings
		 \end{itemize}
\end{slide}

\begin{slide}{Medium-sized application: generic sorting and a database}
	\slideitem{Simple insertion and quicksorts}
		 \begin{itemize}
		 \item standard sorting algorithms such as insertion sort or quicksort can be written in a few lines; \xlink{../code/gensort.html#sorts}{some trade-offs between abstraction and readability are demonstrated here for quicksort}
		 \end{itemize}
	\slideitem{Generalizing to an arbitrary order relation}
		 \begin{itemize}
		 \item using higher-order functions we can easily \xlink{../code/gensort.html#absorder}{generalize our quicksort to work for arbitrary ordering relations}
		 \end{itemize}
	\slideitem{Sorting on extracted "fields"}
		 \begin{itemize}
		 \item now, given some more structured data, we can \xlink{../code/gensort.html#fields}{succinctly express sorts by different criteria}
		 \end{itemize}
	\slideitem{Simultaneous sorting}
		 \begin{itemize}
		 \item we can even extend our sorting function to use two relations on the same data, thus providing \xlink{../code/gensort.html#fields}{independent simultaneous sorts}
		 \end{itemize}
	\slideitem{A simple academic course database}
		 \begin{itemize}
		 \item a type definition and a few utility functions provide us with \xlink{../code/gensort.html#courses}{a simple database of academic courses}
		 \end{itemize}
	\slideitem{Derived lexicographic orderings}
		 \begin{itemize}
		 \item a little bit of logical manipulation allows us to extend any pair (or list) of ordering relations to \xlink{../code/gensort.html#lexi}{provide a lexicographic sort}
		 \end{itemize}
\end{slide}

\begin{slide}{Medium-sized application: arithmetic expression processor}
	\slideitem{An arithmetic expression parser and processor}
		 This example shows how a simple parser and evaluator can be defined for maximum flexibility using polymorphic types and higher-order functions.
	\slideitem{Token type and scanner}
		 \begin{itemize}
		 \item \xlink{../code/expr.html#scan}{a simple type of alternatives and a short recursive function} suffice to transform strings into lists of tokens
		 \end{itemize}
	\slideitem{Tree type and parser (from concrete to abstract)}
		 \begin{itemize}
		 \item our parser is \xlink{../code/expr.html#parse}{parameterized with respect to functions} which might be semantic actions or just tree constructors
		 \end{itemize}
	\slideitem{Operator semantics ("back-end")}
		 \begin{itemize}
		 \item \xlink{../code/expr.html#oper}{a simple database of operators and their meanings} takes advantage of Haskell's ability to store functions in lists
		 \end{itemize}
	\slideitem{Evaluation (and deforestation with folds)}
		 \begin{itemize}
		 \item \xlink{../code/expr.html#tree}{a data type of abstract syntax trees} allows us to hold onto parse data ... but we can also choose to apply semantic actions immediately in order to evaluate an expression
		 \end{itemize}
	\slideitem{Formatting/pretty-printing (in various forms)}
		 \begin{itemize}
		 \item expressions "frozen" in trees can be \xlink{../code/expr.html#print}{printed in different formats} just by varying a "fixity" parameter
		 \end{itemize}
	\slideitem{Variations on multi-parsing (pair of parsers, parser of pairs)}
		 \begin{itemize}
		 \item we can simultaneously parse and evaluate by using \xlink{../code/expr.html#pair}{a pair of parsers or a parser on pairs}
		 \end{itemize}
	\slideitem{Traced calculations}
		 \begin{itemize}
		 \item we can even extend our notion of output to include  \xlink{../code/expr.html#trace}{a complete calculation history, annotated with intermediate terms}
		 \end{itemize}
	\slideitem{Interactivity (at outer entry level)}
		 \begin{itemize}
		 \item all of these operations (evaluation, formatting, tracing) can be accommodated in  \xlink{../code/expr.html#interact}{a single, generic command-line interface}
		 \end{itemize}
\end{slide}

\begin{slide}{An overview of larger-scale projects}
	\slideitem{The Haskore music system (and other DSLs)}
		 Paul Hudak at Yale has defined a powerful language for describing musical structures in abstract terms based on Haskell (see the \xlink{http://haskell.org/haskore/}{Haskore Project} website)
		 \par
		 In general, Haskell's abstraction features make it ideal for defining {\bf domain-specific languages} as Haskell libraries
	\slideitem{The Fran and Pan graphics projects}
		 Conal Elliot at Microsoft Research has developed a couple of libraries, {\bf Fran} and {\bf Pan}, which allow a very high-level way to specify \xlink{../pics/}{complex graphics, animations and interactive animations}
		 \par
		 In Fran, for example, an interactive, single-player "Pong" game can be written in less than 20 lines, using concepts such as integration to express the relationship between velocity and position
	\slideitem{GUI projects}
		 A number of graphical user interface libraries are listed on the Haskell home page, ranging from low-level interfaces to traditional C libraries, to high-level, purely-functional characterizations
		 \par
		 (see the \xlink{http://haskell.org/libraries/#guigs}{GUI library section of the Haskell homepage} for more details
	\slideitem{The Galois Connections ray-tracer}
		 Every year the {\it International Conference on Functional Programming} holds a 72-hour "challenge problem" contest; last year's problem involved writing a 3-D ray-tracer which compiles a scene-description language into rendered output
		 \par
		 a local team from Galois Connections  managed to achieve 2nd-place standing for their entry
\end{slide}

\begin{slide}{Haskell's place in Computer Science and CS education}
	\slideitem{Haskell at Willamette}
		 All of Willamette's courses are taught in Java, with the exception of the FP course, which uses Haskell
	\slideitem{Haskell as a fresh perspective}
		 Because of its non-standard model of computation and its powerful abstraction features, Haskell can serve to positively influence student's design skills, even in other languages
	\slideitem{Haskell for Discrete Mathematics}
		 Rex Page has an \xlink{<http://www.cs.ou.edu/~beseme/>}{NSF project at U Oklahoma called Beseme} which seeks to provide runnable implementations on traditional discrete math topics
		 \par
		 Rex uses \xlink{http://www.amazon.com/exec/obidos/ASIN/1852330899/qid=1002009396/sr=1-1/ref=sr_1_4_1/102-7018854-4544137}{Hall and O'Donnel's "Discrete Mathematics Using a Computer"} as a textbook
	\slideitem{Haskell as "programming for mathematicians"}
		 to turn the tables a bit, Haskell's mathematical flavor and high-level approach make it ideal for use as a first language for math students
\end{slide}\nl

\end{presentation}

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