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UNIX example figures.
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92
thesis.tex
92
thesis.tex
@@ -54,7 +54,7 @@
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\usepackage{tikz}
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\usetikzlibrary{fit,calc,trees,positioning,arrows,chains,shapes.geometric,%
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decorations.pathreplacing,decorations.pathmorphing,shapes,%
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matrix,shapes.symbols,intersections}
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matrix,shapes.symbols,intersections,tikzmark}
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\usepackage[customcolors,shade]{hf-tikz} % Shaded backgrounds.
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\hfsetfillcolor{gray!40}
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@@ -2011,18 +2011,18 @@ and demonstrate how we can use the power of (deep) effect handlers to
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implement a tiny operating system that supports multiple users,
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time-sharing, and file i/o.
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%
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The operating system will be a variation of UNIX~\cite{RitchieT74},
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The operating system will be a variation of \UNIX{}~\cite{RitchieT74},
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which we will call \OSname{}.
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%
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To make the task tractable we will occasionally jump some hops and
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make some simplifying assumptions, nevertheless the resulting
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implementation will capture the essence of a UNIX-like operating
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implementation will capture the essence of a \UNIX{}-like operating
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system.
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%
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The implementation will be composed of several small modular effect
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handlers, that each handles a particular set of system commands. In
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this respect, we will truly realise \OSname{} in the spirit of the
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UNIX philosophy~\cite[Section~1.6]{Raymond03}. The implementation of
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\UNIX{} philosophy~\cite[Section~1.6]{Raymond03}. The implementation of
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the operating system will showcase several computational effects in
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action including \emph{dynamic binding}, \emph{nondeterminism}, and
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\emph{state}.
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@@ -2030,22 +2030,22 @@ action including \emph{dynamic binding}, \emph{nondeterminism}, and
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\subsection{Basic i/o}
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\label{sec:tiny-unix-bio}
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The file system is a cornerstone of UNIX as the notion of \emph{file}
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in UNIX provides a unified abstraction for storing text, interprocess
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The file system is a cornerstone of \UNIX{} as the notion of \emph{file}
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in \UNIX{} provides a unified abstraction for storing text, interprocess
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communication, and access to devices such as terminals, printers,
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network, etc.
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%
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Initially, we shall take a rather basic view of the file system. In
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fact, our initial system will only contain a single file, and
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moreover, the system will only support writing operations. This system
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hardly qualifies as a UNIX file system. Nevertheless, it serves a
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hardly qualifies as a \UNIX{} file system. Nevertheless, it serves a
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crucial role for development of \OSname{}, because it provides the
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only means for us to be able to observe the effects of processes.
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%
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We defer development of a more advanced file system to
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Section~\ref{sec:tiny-unix-io}.
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Much like UNIX we shall model a file as a list of characters, that is
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Much like \UNIX{} we shall model a file as a list of characters, that is
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$\UFile \defas \List~\Char$. For convenience we will use the same
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model for strings, $\String \defas \List~\Char$, such that we can use
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string literal notation to denote the $\strlit{contents of a file}$.
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@@ -2164,7 +2164,7 @@ We can now write some contents to the file and observe the effects.
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\subsection{Dynamic binding: user-specific environments}
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\label{sec:tiny-unix-env}
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In UNIX an environment maps keys to string-values. A key-value pair is
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In \UNIX{} an environment maps keys to string-values. A key-value pair is
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referred to as an \emph{environment variable}. Each user gets their
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own environment with their own set of environment variables. Some
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environment variable names are common to all environments, but their
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@@ -2245,7 +2245,7 @@ an arbitrary number of variables. This can be done by parameterising
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the $\Ask$ operation by some name representation (e.g. a string),
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which the environment handler can use to index into a list of string
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values. In case the name is unbound the environment handler can
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embrace UNIX's laissez-faire attitude and resume with the empty
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embrace \UNIX{}'s laissez-faire attitude and resume with the empty
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string.
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\paragraph{Session management}
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@@ -2369,6 +2369,59 @@ string.
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\subsection{State: file i/o}
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\label{sec:tiny-unix-io}
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\begin{figure}
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\centering
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\begin{tabular}[t]{| l |}
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\hline
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\multicolumn{1}{| c |}{\textbf{Directory}} \\
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\hline
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\strlit{hamlet}\tikzmark{hamlet}\\
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\hline
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\strlit{ritchie.txt}\\
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\hline
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\multicolumn{1}{| c |}{$\cdots$}\\
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\hline
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\strlit{act3}\\
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\hline
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\multicolumn{1}{| c |}{$\cdots$}\\
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\hline
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\strlit{stdout}\\
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\hline
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\end{tabular}
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\hspace{1.5cm}
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\begin{tabular}[t]{| c |}
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\hline
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\multicolumn{1}{| c |}{\textbf{I-List}} \\
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\hline
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2\\
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\hline
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1\tikzmark{hamletino}\\
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\hline
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\multicolumn{1}{| c |}{$\cdots$}\\
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\hline
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1\\
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\hline
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\end{tabular}
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\hspace{1.5cm}
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\begin{tabular}[t]{| l |}
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\hline
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\multicolumn{1}{| c |}{\textbf{Data region}} \\
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\hline
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\strlit{UNIX is basically...}\\
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\hline
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\tikzmark{hamletdr}\strlit{To be, or not to be...}\\
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\hline
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\multicolumn{1}{| c |}{$\cdots$}\\
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\hline
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\strlit{}\\
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\hline
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\end{tabular}
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\tikz[remember picture,overlay]\draw[->,thick] ([xshift=1.3cm,yshift=0.1cm]pic cs:hamlet) -- ([xshift=-0.85cm,yshift=0.1cm]pic cs:hamletino) node[] {};
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\tikz[remember picture,overlay]\draw[->,thick] ([xshift=0.62cm,yshift=0.1cm]pic cs:hamletino) -- ([xshift=-0.23cm,yshift=0.1cm]pic cs:hamletdr) node[] {};
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\caption{\UNIX{} directory, i-list, and data region mappings}\label{fig:unix-mappings}
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\end{figure}
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\[
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\State~\alpha \defas \{\Get:\UnitType \opto \alpha;\Put:\alpha \opto \UnitType\}
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\]
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@@ -2402,6 +2455,25 @@ string.
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\el
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\]
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\begin{figure}
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\centering
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\begin{tikzpicture}[node distance=4cm,auto,>=stealth']
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\node[] (server) {\bfseries Bob (server)};
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\node[left = of server] (client) {\bfseries Alice (client)};
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\node[below of=server, node distance=5cm] (server_ground) {};
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\node[below of=client, node distance=5cm] (client_ground) {};
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%
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\draw (client) -- (client_ground);
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\draw (server) -- (server_ground);
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\draw[->] ($(client)!0.25!(client_ground)$) -- node[rotate=-6,above,scale=0.7,midway]{SYN 42} ($(server)!0.40!(server_ground)$);
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\draw[<-] ($(client)!0.56!(client_ground)$) -- node[rotate=6,above,scale=0.7,midway]{SYN 84;ACK 43} ($(server)!0.41!(server_ground)$);
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\draw[->] ($(client)!0.57!(client_ground)$) -- node[rotate=-6,above,scale=0.7,midway]{ACK 44} ($(server)!0.72!(server_ground)$);
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\end{tikzpicture}
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\caption{Sequence diagram for the TCP handshake example.}\label{fig:tcp-handshake}
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\end{figure}
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\paragraph{TCP threeway handshake}
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% The existing literature already contain an extensive amount of
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% introductory examples of programming with (deep) effect
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% handlers~\cite{KammarLO13,Pretnar15,Leijen17}.
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