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+@code{(require 'hilbert-fill)}
+@ftindex hilbert-fill
+
+@noindent
+@cindex Peano
+@cindex Hilbert
+@cindex Space-Filling
+The @dfn{Peano-Hilbert Space-Filling Curve} is a one-to-one mapping
+@cindex Peano-Hilbert Space-Filling Curve
+between a unit line segment and an @var{n}-dimensional unit cube.
+
+@noindent
+The integer procedures map the non-negative integers to an
+arbitrarily large @var{n}-dimensional cube with its corner at the
+origin and all coordinates are non-negative.
+
+@noindent
+For any exact nonnegative integers @var{scalar} and @var{rank},
+
+@example
+(= @var{scalar} (hilbert-coordinates->integer
+           (integer->hilbert-coordinates @var{scalar} @var{rank})))
+                                       @result{} #t
+@end example
+
+
+@defun integer->hilbert-coordinates scalar rank
+
+Returns a list of @var{rank} integer coordinates corresponding to exact
+non-negative integer @var{scalar}.  The lists returned by @code{integer->hilbert-coordinates} for @var{scalar} arguments
+0 and 1 will differ in the first element.
+@end defun
+
+@defun hilbert-coordinates->integer coords
+
+Returns an exact non-negative integer corresponding to @var{coords}, a list
+of non-negative integer coordinates.
+@end defun