10.21 Array Operations—library(logarr)

This libary module provides extendible arrays with logarithmic access time. Please note: the atom $ is used to indicate an unset element, and the functor $/4 is used to indicate a subtree. In general, array elements whose principal function symbol is $ will not work.

Exported predicates:

new_array(-A) returns a new empty array A.

is_array(+A)

checks whether A is an array.

alist(+Array, -List)

returns a list of pairs Index-Element of all the elements of Array that have been set.

aref(+Index, +Array, -Element)

unifies Element with Array[Index], or fails if Array[Index] has not been set.

arefa(+Index, +Array, -Element)

is as aref/3, except that it unifies Element with a new array if Array[Index] is undefined. This is useful for multidimensional arrays implemented as arrays of arrays.

arefl(+Index, +Array, -Element)

is as aref/3, except that Element appears as [] for undefined cells.

aset(+Index, +Array, +Element, -NewArray)

unifies NewArray with the result of setting Array[Index] to Element.