From: Mart Lubbers <mart@martlubbers.net>
Date: Tue, 13 Jun 2017 12:57:01 +0000 (+0200)
Subject: acknowledgements and parametric lenses
X-Git-Tag: hand-in~89^2
X-Git-Url: https://git.martlubbers.net/?a=commitdiff_plain;h=f2e00e1e8180d06fc78f66ca99ea07f583f9056f;p=msc-thesis1617.git

acknowledgements and parametric lenses
---

diff --git a/acknowledgements.tex b/acknowledgements.tex
index a8e7ea5..7dd444f 100644
--- a/acknowledgements.tex
+++ b/acknowledgements.tex
@@ -1 +1,7 @@
-My thanks and gratitude goes to\ldots
+I would like to thank everyone that helped me writing thesis. This includes but
+is not limited to Rinus and Pieter for the support, supervision and weekly
+sparring. Bas for providing the needed \gls{iTasks} support. Arjan for the
+sparring and coffee. George, Camil and others\todo{proofreaders}\ for
+proofreading and  Camil for lifting \emph{Cloogle} to a solid search engine I
+used daily. Finally I would like to thank my family, friends and wife for
+listening to a year of endless rambling on this.
diff --git a/methods.top.tex b/methods.top.tex
index b54b50f..ec330c9 100644
--- a/methods.top.tex
+++ b/methods.top.tex
@@ -67,7 +67,6 @@ specialization instances for these functions and show an according interface.
 Generated interfaces can be modified with decoration operators.
 
 \section{Combinators}
-\todo{check and refine}
 \Glspl{Task} can be combined using so called \gls{Task}-combinators.
 Combinators describe relations between \glspl{Task}. \Glspl{Task} can be
 combined in parallel, sequenced and their result values can be converted to
@@ -121,23 +120,25 @@ Listing~\ref{lst:combinators}.
 
 \section{Shared Data Sources}
 \Glspl{SDS} are an abstraction over resources that are available in the world
-or in the \gls{iTasks} system. The shared data can be a file on disk, it can be
-the time, a random integer or just some data stored in memory. The actual
+or in the \gls{iTasks} system. The shared data can be a file on disk, the
+system time, a random integer or just some data stored in memory. The actual
 \gls{SDS} is just a record containing functions on how to read and write the
-source. In these functions the \CI{*IWorld} which in turn contains the real
-program \CI{*World}. Accessing the outside world is required for interacting
-with it and thus the functions can access files on disk, raw memory, other
-shares and combine shares.
+source. In these functions the \CI{*IWorld} --- which in turn contains the real
+program \CI{*World} --- is available. Accessing the outside world is required
+for interacting with it and thus the functions can access files on disk, raw
+memory, other shares and hardware.
 
 The basic operations for \glspl{SDS} are get, set and update. The signatures
 for these functions are shown in Listing~\ref{lst:shares}. By default, all
 shares are files containing a \gls{JSON} encoded version of the object and thus
 are persistent between restarts of the program. Library functions for shares
 residing in memory are available as well. The three main operations on shares
-are atomic in the sense that during reading no other tasks are executed.
-
-The basic type for \glspl{SDS} has three \todo{parametric
-lenses}\cite{domoszlai_parametric_2014}.
+are atomic in the sense that during reading no other tasks are executed. The
+system provides useful functions to transform, map and combine \glspl{SDS}
+using combinators. The system also provides functionality to inspect the value
+of a \gls{SDS} and act upon a change. \Glspl{Task} waiting on a \gls{SDS} to
+change are notified when needed. This results in low resource usage because
+\glspl{Task} are never constantly inspecting \gls{SDS} values but are notified.
 
 \begin{lstlisting}[%
 	label={lst:shares},caption={\Gls{SDS} functions}]
@@ -154,3 +155,33 @@ upd :: (r -> w) (ReadWriteShared r w)           -> Task w | iTask r & iTask w
 
 sharedStore :: String a -> Shared a | JSONEncode{|*|}, JSONDecode{|*|}
 \end{lstlisting}
+
+\section{Parametric Lenses}
+\Glspl{SDS} can contain complex data structures such as lists, trees and even
+resources in the outside world. Sometimes, an update action only updates a part
+of the resource. When this happens, all waiting \glspl{Task} looking at the
+resource are notified of the update. However, it may be the case that
+\glspl{Task} where only looking at parts of the structure that was not updated.
+To solve this problem, parametric lenses were
+introduced~\cite{domoszlai_parametric_2014}.
+
+Parametric lenses add a type variable to the \gls{SDS} that is in the current
+library functions fixed to \CI{()}. When a \gls{SDS} executes a write
+operation it also provides the system with a notification predicate. This
+notification predicate is a function \CI{p -> Bool} where \CI{p} is the
+parametric lens type. This allows programmers to create a big share, and have
+\glspl{Task} only look at parts of the big share. This technique is used in the
+current system in memory shares. The \CI{IWorld} contains a map that is
+accessible through an \gls{SDS}. While all data is stored in the map, only
+\glspl{Task} looking at a specific entry are notified when the structure is
+updated. The type of the parametric lens is the key in the map.
+
+Functionality for setting parameters is added in the system. The most important
+function is the \CI{sdsFocus} function. This function is listed in
+Listing~\ref{lst:focus} and allows the programmer to fix the parametric lens to
+a value.
+
+\begin{lstlisting}[label={lst:focus},
+	caption={Parametric lens functions}]
+sdsFocus :: p (RWShared p r w) -> RWShared p` r w | iTask p
+\end{lstlisting}