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Tidied up the HATRA paper

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ajeffrey@roblox.com 2021-07-15 12:14:37 -05:00
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@ -7,7 +7,7 @@
\begin{document} \begin{document}
\title{The Goals of the Luau Type System} \title{Position Paper: Goals of the Luau Type System}
\author{Andy Friesen} \author{Andy Friesen}
\author{Alan Jeffrey} \author{Alan Jeffrey}
@ -20,7 +20,7 @@
} }
\begin{abstract} \begin{abstract}
A position paper about the goals Luau type system. A position paper about goals of the Luau type system.
\end{abstract} \end{abstract}
\maketitle \maketitle
@ -30,8 +30,8 @@
The Roblox~\cite{Roblox} platform allows anyone to create shared, The Roblox~\cite{Roblox} platform allows anyone to create shared,
immersive, 3D experiences. At the time of writing, there are immersive, 3D experiences. At the time of writing, there are
approximately eight million experiences available on Roblox, created approximately eight million experiences available on Roblox, created
by eight million developers. Roblox developers are often young, for by eight million developers. Roblox creators are often young, for
example there are over 200 Roblox coding camps in over 65 countries example there are over 200 Roblox kids' coding camps in over 65 countries
listed at~\cite{AllEducators}. listed at~\cite{AllEducators}.
The Luau programming language~\cite{Luau} is the scripting language The Luau programming language~\cite{Luau} is the scripting language
@ -39,8 +39,8 @@ used by developers of Roblox experiences. Luau is derived from the Lua
programming language~\cite{Lua}, with additional capabilities, programming language~\cite{Lua}, with additional capabilities,
including a type inference engine. including a type inference engine.
This paper will discuss some of the goals of the Luau type system, and This paper will discuss some of the goals of the Luau type system,
why those goals are slightly different from other type systems. focusing on where the goals are different from those of other type systems.
\section{Human Aspects} \section{Human Aspects}
\subsection{Heterogenous developer community} \subsection{Heterogenous developer community}
@ -52,7 +52,7 @@ Quoting a 2020 report \cite{RobloxDevelopers}:
\item There are now 345,000 developers on the platform who are monetizing their games. \item There are now 345,000 developers on the platform who are monetizing their games.
\end{itemize} \end{itemize}
This demonstrates how heterogenous the Roblox developer community is: This demonstrates how heterogenous the Roblox developer community is:
developers of experiences with plays measured in billions on the same developers of experiences with plays measured in billions are on the same
platform as children first learning to code. Moreover, \emph{both of platform as children first learning to code. Moreover, \emph{both of
these groups are important}, as the professional development studios these groups are important}, as the professional development studios
bring high-quality experiences to the platform, and the beginning creators bring high-quality experiences to the platform, and the beginning creators
@ -65,33 +65,33 @@ learners. A learner will download Roblox Studio (the IDE) with an
experience in mind, often designing an obstacle course (an ``obby'') experience in mind, often designing an obstacle course (an ``obby'')
to play in with their friends. to play in with their friends.
The user experience of developing a Roblox experience is The user experience of developing a Roblox experience is primarily a
primarily a 3D interactive one, where the user designs and deploys 3D 3D interactive one, seen in Fig.~\ref{fig:studio}(a). The user designs
assets such as terrain, parts and joints, and provides them with and deploys 3D assets such as terrain, parts and joints, and provides
physics attributes such as mass and orientation. The user can interact them with physics attributes such as mass and orientation. The user
with the experience in Studio, and deploy it to a Roblox server so anyone with can interact with the experience in Studio, and deploy it to a Roblox
the Roblox app can play it. server so anyone with the Roblox app can play it.
\begin{figure} \begin{figure}
\includegraphics[width=0.48\textwidth]{studio-mow.png} \includegraphics[width=0.48\textwidth]{studio-mow.png}
\includegraphics[width=0.48\textwidth]{studio-script-editor.png} \includegraphics[width=0.48\textwidth]{studio-script-editor.png}
\caption{Roblox Studio's 3D environment editor, and script editor} \caption{Roblox Studio's 3D environment editor (a), and script editor (b)}
\label{fig:studio}
\end{figure} \end{figure}
At some point during experience design, the user of Studio has a need At some point during experience design, the user of Studio has a need
which can't be met by the physics engine alone. ``The stairs should which can't be met by the physics engine alone. ``The stairs should
light up when a player walks on them'' or ``a firework is set off light up when a player walks on them'' or ``a firework is set off
every few seconds.'' At this point they will discover the script every few seconds.'' At this point they will discover the script
editor, and the Luau programming language. editor, seen in Fig.~\ref{fig:studio}(b), and the Luau programming language.
This workflow is different from many initial exposures to programming, This onboarding experience is different from many initial exposures to
in that by the time the user first opens the script editor, they have programming, in that by the time the user first opens the script
already built much of their creation, and have a very specific editor, they have already built much of their creation, and have a
concrete aim. very specific concrete aim. It suggests a Luau goal for helping the
majority of creators: \emph{support learning how to perform specific
This workflow suggests a Luau goal for helping the majority of tasks} (for example through autocomplete suggestions and
creators: \emph{support learning how to perform specific tasks} (for documentation).
example through autocomplete suggestions and documentation).
\subsection{Type-driven development} \subsection{Type-driven development}
@ -136,6 +136,8 @@ Goal: no false positives
- Related to success types? - Related to success types?
- Problems with mutation and avoiding whole-program analysis.
\subsection{Mixing types} \subsection{Mixing types}
Goal: support mixed strict/nonstrict development Goal: support mixed strict/nonstrict development