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\title{Diderot}
\author{
  Gordon Kindlmann \\
  University of Chicago \\
  {\small\tt{}glk@cs.uchicago.edu} \\
\and
  John Reppy \\
  University of Chicago \\
  {\small\tt{}jhr@cs.uchicago.edu} \\
}
\date{\today}

\begin{document}

\maketitle
\thispagestyle{empty}

\section{Introduction}
This document is a semi-formal design of Dedierot.

\section{Types}
The syntax of Diderot types is as follows:
\begin{displaymath}
  \begin{array}{rclr}
    \tau & ::=  & \TYbool & \text{booleans} \\
         & \mid & \TYint & \text{integers} \\
         & \mid & \TYtensor{o}{d} & \text{tensors of order $o$ and dimension $d$} \\
         & \mid & \TYmatrix{n}{m} & \text{$n\times{}m$ matrix} \\
         & \mid & \TYimage{d}{\tau} & \text{image of dimension $d$ and $\tau$ elements}\\
         & \mid & \TYkern{k} & \text{convolution kernel with $k$ derivatives} \\
         & \mid & \TYfield{k}{d}{\tau} & \text{$d$-dimension field of $\tau$ values and $k$ derivatives} \\
  \end{array}%
\end{displaymath}%
where $o\in\Nat$ is the tensor order, $d,n,m\in\SET{2,3}$ are dimensions,
and $k\in\Nat$ is the differentiability of a field.

Some type abbreviations:
\begin{eqnarray*}
  \TYreal & = & \TYtensor{0}{d} \quad\text{for any $d$} \\
  \TYvec{d} & = & \TYtensor{1}{d}
\end{eqnarray*}%

\section{Operations}

\subsection{Scalar operations}
\noindent{}Arithmetic:
\begin{displaymath}
  \BinopTy{{\odot}}{\tau}{\tau}{\tau}
  \qquad\text{for $\odot\in\SET{{+},{-},{*},{/}}$ and $\tau\in\SET{\TYint,\TYreal}$}
\end{displaymath}%

\noindent{}Comparisons:
\begin{displaymath}
  \BinopTy{{\odot}}{\tau}{\tau}{\TYbool}
  \qquad\text{for $\odot\in\SET{{<},{\leq},{=},{\neq}{>},{\geq}}$ and $\tau\in\SET{\TYint,\TYreal}$}
\end{displaymath}%


\subsection{Matrix operations}

\subsection{Tensor operations}

\noindent{}Scalar multiplication:
\begin{displaymath}
  \begin{array}{c}
    \BinopTy{{*}}{\TYreal}{\TYtensor{o}{d}}{\TYtensor{o}{d}} \\
    \BinopTy{{*}}{\TYtensor{o}{d}}{\TYreal}{\TYtensor{o}{d}}
  \end{array}%
\end{displaymath}%

\noindent{}Addition:
\begin{displaymath}
  \BinopTy{{\odot}}{\TYtensor{o}{d}}{\TYtensor{o}{d}}{\TYtensor{o}{d}}
  \qquad\text{for $\odot\in\SET{{+},{-}}$}
\end{displaymath}%

\subsection{Field operations}

\noindent{}Creation from an image:
\begin{displaymath}
  \BinopTy{\OPsample}{\TYkern{k}}{\TYimage{d}{\tau}}{\TYfield{k}{d}{\hat{\tau}}}
  \qquad\text{where $\hat{\tau}$ is the real conversion of $\tau$.}
\end{displaymath}%

\noindent{}Addition:
\begin{displaymath}
  \BinopTy{{\odot}}{\TYfield{k_1}{d}{\tau}}{\TYfield{k_2}{d}{\tau}}{\TYfield{\min(k_1,k_2)}{d}{\tau}}
  \qquad\text{for $\odot\in\SET{{+},{-}}$}
\end{displaymath}%

\noindent{}Differentiation:
\begin{displaymath}
  \UnopTy{\OPdiff}{\TYfield{k}{d}{\tau}}{\TYfield{k-1}{d}{\tau}}
  \qquad\text{for $k > 0$}
\end{displaymath}%

\noindent{}Probing:
\begin{displaymath}
  \BinopTy{@}{\TYfield{k}{d}{\tau}}{\TYvec{d}}{\tau}
\end{displaymath}%

\end{document}