Initial population.

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+% Copyright The Numerical Algorithms Group Limited 1992-94. All rights reserved.
+% !! DO NOT MODIFY THIS FILE BY HAND !! Created by ht.awk.
+\newcommand{\TwoDimensionalArrayXmpTitle}{TwoDimensionalArray}
+\newcommand{\TwoDimensionalArrayXmpNumber}{9.82}
+%
+% =====================================================================
+\begin{page}{TwoDimensionalArrayXmpPage}{9.82 TwoDimensionalArray}
+% =====================================================================
+\beginscroll
+
+The \spadtype{TwoDimensionalArray} domain is used for storing data in a
+%-% \HDindex{array!two-dimensional}{TwoDimensionalArrayXmpPage}{9.82}{TwoDimensionalArray}
+\twodim{} data structure indexed by row and by column.
+Such an array is a homogeneous data structure in that all the entries of
+the array must belong to the same \Language{} domain (although see
+\downlink{``\ugTypesAnyNoneTitle''}{ugTypesAnyNonePage} in Section \ugTypesAnyNoneNumber\ignore{ugTypesAnyNone}).
+Each array has a fixed number of rows and columns specified by the user
+and arrays are not extensible.
+In \Language{}, the indexing of two-dimensional arrays is one-based.
+This means that both the ``first'' row of an array and the ``first''
+column of an array are given the index \spad{1}.
+Thus, the entry in the upper left corner of an array is in position
+\spad{(1,1)}.
+
+
+The operation \spadfunFrom{new}{TwoDimensionalArray} creates
+an array with a specified number of rows and columns and fills the components
+of that array with a specified entry.
+The arguments of this operation specify the number of rows, the number
+of columns, and the entry.
+\xtc{
+This creates a five-by-four array of integers, all of whose entries are
+zero.
+}{
+\spadpaste{arr : ARRAY2 INT := new(5,4,0) \bound{arr}}
+}
+The entries of this array can be set to other integers using
+the operation \spadfunFrom{setelt}{TwoDimensionalArray}.
+
+\xtc{
+Issue this to set the element in the upper left corner of this array to
+\spad{17}.
+}{
+\spadpaste{setelt(arr,1,1,17) \free{arr}\bound{arr1}}
+}
+\xtc{
+Now the first element of the array is \spad{17.}
+}{
+\spadpaste{arr \free{arr1}}
+}
+\xtc{
+Likewise, elements of an array are extracted using the operation
+\spadfunFrom{elt}{TwoDimensionalArray}.
+}{
+\spadpaste{elt(arr,1,1) \free{arr1}}
+}
+\xtc{
+Another way to use these two operations is as follows.
+This sets the element in position \spad{(3,2)} of the array to \spad{15}.
+}{
+\spadpaste{arr(3,2) := 15 \free{arr1}\bound{arr2}}
+}
+\xtc{
+This extracts the element in position \spad{(3,2)} of the array.
+}{
+\spadpaste{arr(3,2) \free{arr2}}
+}
+The operations \spadfunFrom{elt}{TwoDimensionalArray} and
+\spadfunFrom{setelt}{TwoDimensionalArray} come equipped with an error
+check which verifies that the indices are in the proper ranges.
+For example, the above array has five rows and four columns, so if you ask
+for the entry in position \spad{(6,2)} with \spad{arr(6,2)} \Language{}
+displays an error message.
+If there is no need for an error check, you can call the operations
+\spadfunFrom{qelt}{TwoDimensionalArray} and
+\spadfunFromX{qsetelt}{TwoDimensionalArray} which provide the same
+functionality but without the error check.
+Typically, these operations are called in well-tested programs.
+
+\xtc{
+The operations \spadfunFrom{row}{TwoDimensionalArray} and
+\spadfunFrom{column}{TwoDimensionalArray} extract rows and columns,
+respectively, and return objects of \spadtype{OneDimensionalArray} with
+the same underlying element type.
+}{
+\spadpaste{row(arr,1) \free{arr2}}
+}
+\xtc{
+}{
+\spadpaste{column(arr,1) \free{arr2}}
+}
+
+\xtc{
+You can determine the dimensions of an array by calling the
+operations \spadfunFrom{nrows}{TwoDimensionalArray} and
+\spadfunFrom{ncols}{TwoDimensionalArray},
+which return the number of rows and columns, respectively.
+}{
+\spadpaste{nrows(arr) \free{arr2}}
+}
+\xtc{
+}{
+\spadpaste{ncols(arr) \free{arr2}}
+}
+\xtc{
+To apply an operation to every element of an array, use
+\spadfunFrom{map}{TwoDimensionalArray}.
+This creates a new array.
+This expression negates every element.
+}{
+\spadpaste{map(-,arr) \free{arr2}}
+}
+\xtc{
+This creates an array where all the elements are doubled.
+}{
+\spadpaste{map((x +-> x + x),arr) \free{arr2}}
+}
+\xtc{
+To change the array destructively, use
+\spadfunFromX{map}{TwoDimensionalArray} instead of
+\spadfunFrom{map}{TwoDimensionalArray}.
+If you need to make a copy of any array, use
+\spadfunFrom{copy}{TwoDimensionalArray}.
+}{
+\spadpaste{arrc := copy(arr) \bound{arrc}\free{arr2}}
+}
+\xtc{
+}{
+\spadpaste{map!(-,arrc) \free{arrc}}
+}
+\xtc{
+}{
+\spadpaste{arrc \free{arrc}}
+}
+\xtc{
+}{
+\spadpaste{arr  \free{arr2}}
+}
+
+\xtc{
+Use \spadfunFrom{member?}{TwoDimensionalArray} to see if a given element
+is in an array.
+}{
+\spadpaste{member?(17,arr) \free{arr2}}
+}
+\xtc{
+}{
+\spadpaste{member?(10317,arr) \free{arr2}}
+}
+\xtc{
+To see how many times an element appears in an array, use
+\spadfunFrom{count}{TwoDimensionalArray}.
+}{
+\spadpaste{count(17,arr) \free{arr2}}
+}
+\xtc{
+}{
+\spadpaste{count(0,arr) \free{arr2}}
+}
+
+For more information about the operations available for
+\spadtype{TwoDimensionalArray}, issue \spadcmd{)show
+TwoDimensionalArray}.
+For information on related topics, see \downlink{`Matrix'}{MatrixXmpPage}\ignore{Matrix} and
+\downlink{`OneDimensionalArray'}{OneDimensionalArrayXmpPage}\ignore{OneDimensionalArray}.
+\endscroll
+\autobuttons
+\end{page}
+%