521 Multi-dimensional arrays \index{array}are simple nested vectors, they are created with the {\it dim} \index{dim}predicate for a given dimension and size. Access to an element is with the {\it subscript}\index{subscript} predicate (see section \ref{iterationonarray} for an example).
671 \index{iteration, list}\index{list}This concept is used to perform some action on each element of a list. There are two implementations given here. The first uses the {\it do}\index{do loop}\index{loop} loop of ECLiPSe, the second uses recursion\index{recursion} to achieve the same purpose. In the {\it do} loop, the {\it foreach}\index{foreach} keyword describes an action for each element of a list. The first argument (here $X$) is a formal parameter\index{formal parameter} of the loop. At each iteration, it will be bound to one element of the list. The second argument is the list over which we iterate.
786 \index{iteration, array}The next concept is iteration on an array \index{array}structure. We often want to perform some action on each element of a two-dimensional array. 
788 Again, we present two implementations. The first uses nested {\it foreacharg}\index{foreacharg, nested} {\it do} loops to perform some operation $q$ on each element of an array. The second uses nested {\it for}\index{for}\index{loop} loops to iterate over all index combinations $I$ and $J$. This second variant is more complex, and should be used only if we require the index values $I$ and $J$ as well as the matrix element $X$. 
841 This next concept is used to perform some transformation\index{transformation} on each element of a list and to create a list of the transformed elements. At the end, both lists will have the same length, and the elements match, i.e. the first element of the second list is the transformed first element of the first list. 
944 The cuts (!) \index{cut}in the program clauses are very important, as they remove the possibility that a selected element is not included in the filtered list. If we remove the cuts, then the {\it filter} predicate has an exponential number of ``solutions''. Only the first solution will be correct, on backtracking we will decide to reject elements which satisfy the test criterion and we will explore all combinations until we reach the empty list as the last ``solution''.
998 It is important to note that the recursive call in the second clause continues with the combined element $C$, since it may be combined with more elements of the rest of the list $R$.
1044 \index{minimum}This concept selects the smallest element of a list according to some comparison operator {\it better}.
1065 This implementation of minimum fails if the input list has no elements. This means that somewhere else in the program we have to handle the case where the input list is empty. This seems to be the most clear definition of minimum, an empty list does not have a smallest element.
1071 \index{best and rest}This concept is an extension of the minimum concept. It not only returns the best element in the input list, but also the rest of the original list without the best element. This rest can then be used for example to select another element, and so on.
1245 The second argument of {\it group\_lp} serves as an accumulator\index{accumulator} to collect items with the same key. As long as the next item uses the same key, it is put into this accumulator (2nd clause). If the remaining list is empty (1st clause) or it starts with an element of a different key (3rd clause), the accumulated list is put into the output list.
1366 The result is a list of terms {\it pair(X, Y)}, where $X$ is an element of list $L$ and $Y$ is an element of list $K$.
1432 This concept creates ordered pairs\index{ordered pairs}\index{pairs, ordered} of entries from a list. Each combination where the first element occurs in the input list before the second element is created exactly once.
2159 \item[foreach] \index{foreach}iterate over each element in a list
2187 \item[subscript/3] \index{subscript/3}get an element of an array
2211 \item[with] \index{with}access element(s) in named structure

Indexes created Tue Jul 09 22:07:09 MDT 2024