\section{Array Shaping}

\label{sec:array-shaping}

A pointer variable can be shaped to a multi-dimensional array to facilitate

data access. This is achieved by a \plc{shape-operator} casted in front of

a pointer (lvalue expression):

\begin{description}

\item[]\hspace*{5mm}\code{([$s_1$][$s_2$]...[$s_n$])}\plc{pointer}

\end{description}

where each $s_i$ is an integral-type expression of positive value.

The shape-operator can appear in either the \plc{motion-clause}

of the \code{target}~\code{update} directive or the \code{depend} clause.

The following example shows the use of the shape-operator in the

\code{target}~\code{update} directive. The shape-operator \code{([nx][ny+2])}

casts pointer variable $a$ to a 2-dimentional array of size

\plc{nx}$\times$\plc{(ny+2)}. The resulting array is then accessed as

array sections (such as \code{[0:nx][1]} and \code{[0:nx][ny]})

in the \code{from} or \code{to} clause for transferring two columns of

noncontiguous boundary data from or to the device.

Note the use of additional parentheses

around the shape-operator and $a$ to ensure the correct precedence

over array-section operations.

\cnexample{array_shaping}{1}