Added text for the erlang code example about exposing functionality to the GDL
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Jonatan Pålsson
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2 changed files with 193 additions and 44 deletions
237
report.lyx
237
report.lyx
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@ -693,6 +693,9 @@ Citation needed
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Users will notice this in low uptime and many crashes.
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This is a problem that has existed and been resolved in other industries.
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In the telecom industry solutins to similar problems have been found.
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\end_layout
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\begin_layout Standard
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\begin_inset ERT
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status open
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@ -728,10 +731,6 @@ textbf{Uptime}}{The amount of time a system is available and functions}
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\end_inset
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\end_layout
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\begin_layout Standard
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A common figure often used in telecoms is that of
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\emph on
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the nine nines
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@ -4063,7 +4062,7 @@ status open
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{
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\backslash
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tt X, Var,} and {
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tt X, Var}, and {
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\backslash
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tt Global}
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\end_layout
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@ -4082,16 +4081,13 @@ Atoms
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\series default
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\emph default
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start with lower case letters,
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for example:
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\lang english
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start with lower case letters, for example:
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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{
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\backslash
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tt atom, a}
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\end_layout
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@ -4109,10 +4105,7 @@ Functions
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are defined starting with an atom for the name, parenthesis containing
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parameters, an arrow, a function body and finally a dot marking the end
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of a function.
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\lang english
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\begin_inset ERT
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status open
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@ -4182,7 +4175,7 @@ tt
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\backslash
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{atom1, atom2, atom3
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\backslash
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}}
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}}.
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\end_layout
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\end_inset
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@ -4208,7 +4201,7 @@ tt [1,2,3]}
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\end_inset
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.
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\end_layout
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\begin_layout Itemize
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@ -4229,7 +4222,7 @@ tt "Hello world"}
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\end_inset
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.
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\end_layout
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\begin_layout Itemize
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@ -4254,21 +4247,7 @@ tt
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\end_inset
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\end_layout
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\begin_layout Standard
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\begin_inset Note Note
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status open
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\begin_layout Plain Layout
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Here we can have a more in-depth look at why Erlang was used, and outline
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the characteristics of EWrlang that we make use of in the GGS.
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\end_layout
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\end_inset
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.
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\end_layout
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\begin_layout Section
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@ -4314,10 +4293,29 @@ localstorage
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by a call for the world object.
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Interaction with the players is done the same way using the player object
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instead.
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The localstorage is a convenient way to store globals and other variables
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seperated from the game state.
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The localstorage is a convenient way to store globals and other data seperated
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from the game state.
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In section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sub:Exposing-Erlang-functionality"
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\end_inset
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a concrete example of the implementation of the localStorage and world
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objects is given.
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\begin_inset Note Note
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status open
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\begin_layout Plain Layout
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Unique id:s called gametokens are generated for hosted games so that they
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are not mixed up.
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-- good text, integrate more.
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\end_layout
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\end_inset
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\begin_inset ERT
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status open
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@ -4337,23 +4335,174 @@ textbf{WebStorage}}{A new standard for letting websites store data on visitors'
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\end_layout
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\begin_layout Subsection
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Exposing Erlang functionality to the GDL VM
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\end_layout
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\begin_layout Standard
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\begin_inset Note Note
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status open
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\begin_layout Plain Layout
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Prior to this section, the Erlang syntax has to be briefly explained.
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I think the 'usage of erlang' section is a good place to do this in.
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\end_layout
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Exposing Erlang functionality to the GDL VM
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\begin_inset CommandInset label
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LatexCommand label
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name "sub:Exposing-Erlang-functionality"
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\end_inset
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\end_layout
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\begin_layout Standard
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This section contains a concrete example of how the localStorage and world
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objects are exposed to a GDL VM.
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The example comes from the GGS prototype, which uses JavaScript powered
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by Google V8 as its GDL VM.
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\end_layout
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\begin_layout Standard
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The code given in
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "alg:exposing-erlang"
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\end_inset
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is specific to V8 and JavaScript, however implementations for different
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GDL:s, or different JavaScript VM:s should be similar.
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\end_layout
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\begin_layout Standard
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In JavaScript is is common to use a top level object, called a global object,
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to establish a global scope.
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This allows declaration of global variables and functions.
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To gain access to the global object in the GGS, the
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt erlv8
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\backslash
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_vm:global(..)}
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\end_layout
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\end_inset
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function on line 2 of the example is used.
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Using the global object, declarations of the world and GGS object can be
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placed in the global scope.
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\end_layout
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\begin_layout Standard
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt Global:set
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\backslash
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_value(..)}
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\end_layout
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\end_inset
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is a call to the global object, declaring new objects in the global scope.
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On line 4 the GGS object is declared.
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By accessing
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt GGS.localStorage }
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\end_layout
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\end_inset
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from within the GDL, access to the localstorage is provided, thus the localstor
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age must be connected to the GGS object, this can be seen in line 5.
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\end_layout
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\begin_layout Standard
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Both the GGS and localStorage objects are dummy objects, which provide no
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functionality, these two objects are simply placed in the GDL for the purpose
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clearing up the code.
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In order to perform an action using the GGS and localStorage objects, the
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt getItem} and {
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\backslash
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tt setItem}
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\end_layout
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\end_inset
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functions must be used.
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These items are directly connected to the database module of the GGS, which
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is discussed in more detail in
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sub:The-database-module"
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\end_inset
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.
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\end_layout
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\begin_layout Standard
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Similarly the functions
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt sendCommand, sendCommandToAll} and {
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\backslash
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tt setTimeout}
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\end_layout
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\end_inset
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are directly connected to a piece of code in the GGS which performs the
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desired action.
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The
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt sendCommand}
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\end_layout
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\end_inset
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functions are used to send commands or text to participants of the table.
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The
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\begin_inset ERT
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status open
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\begin_layout Plain Layout
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{
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\backslash
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tt setTimeout}
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\end_layout
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\end_inset
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function introduces timeouts to the V8 engine, which are not available
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per default.
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\end_layout
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\begin_layout Standard
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\begin_inset Float algorithm
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wide false
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