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author | Thomas Bushnell, BSG <tb@debian.org> | 2005-11-02 14:55:21 -0800 |
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committer | Bryan Newbold <bnewbold@robocracy.org> | 2017-02-20 00:05:32 -0800 |
commit | 34c54a22ff7818bb8b38ef4d9c87dbbcb221ba73 (patch) | |
tree | 1189d06a81277bcf8539b0260a69a19f6038effb /phil-spc.txi | |
parent | 611b3db17894e5fdc0db3d49eaf6743d27b44233 (diff) | |
parent | 5145dd3aa0c02c9fc496d1432fc4410674206e1d (diff) | |
download | slib-c93d164f90a2c6f04bbccce83704a763f8abc8b3.tar.gz slib-c93d164f90a2c6f04bbccce83704a763f8abc8b3.zip |
Import Debian changes 3a2-1debian/3a2-1
slib (3a2-1) unstable; urgency=low
* New upstream release.
* Acknowledge NMU. (Closes: #281809)
* Makefile: Don't hack Makefile; use rules instead.
* debian/rules: Set on make invocations: prefix, htmldir, TEXI2HTML.
* debian/rules (clean): Clean more stuff here.
* Makefile: Comment out old rule for $(htmldir)slib_toc.html. Instead,
specify directly that the texi2html invocation produces that file.
* debian/rules (binary-indep): Find web files in slib subdir.
* debian/control (Build-Depends-Indep): Go back to using scm.
Diffstat (limited to 'phil-spc.txi')
-rw-r--r-- | phil-spc.txi | 130 |
1 files changed, 126 insertions, 4 deletions
diff --git a/phil-spc.txi b/phil-spc.txi index 1193c6c..ac1743c 100644 --- a/phil-spc.txi +++ b/phil-spc.txi @@ -2,12 +2,13 @@ @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 +The @dfn{Hilbert Space-Filling Curve} is a one-to-one mapping +@cindex Hilbert Space-Filling Curve between a unit line segment and an @var{n}-dimensional unit cube. +This implementation treats the nonnegative integers either as +fractional bits of a given width or as nonnegative integers. @noindent The integer procedures map the non-negative integers to an @@ -15,7 +16,8 @@ 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}, +For any exact nonnegative integer @var{scalar} and exact integer +@var{rank} > 2, @example (= @var{scalar} (hilbert-coordinates->integer @@ -23,16 +25,136 @@ For any exact nonnegative integers @var{scalar} and @var{rank}, @result{} #t @end example +When treating integers as @var{k} fractional bits, + +@example +(= @var{scalar} (hilbert-coordinates->integer + (integer->hilbert-coordinates @var{scalar} @var{rank} @var{k})) @var{k}) + @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. + + +@defunx integer->hilbert-coordinates scalar rank k + +@var{scalar} must be a nonnegative integer of no more than +@code{@var{rank}*@var{k}} bits. + +@code{integer->hilbert-coordinates} Returns a list of @var{rank} @var{k}-bit nonnegative integer +coordinates corresponding to exact non-negative integer @var{scalar}. The +curves generated by @code{integer->hilbert-coordinates} have the same alignment independent of +@var{k}. @end defun + @defun hilbert-coordinates->integer coords + +@defunx hilbert-coordinates->integer coords k Returns an exact non-negative integer corresponding to @var{coords}, a list of non-negative integer coordinates. @end defun + +@subsubsection Gray code + +@cindex Gray code +@noindent +A @dfn{Gray code} is an ordering of non-negative integers in which +@cindex Gray code +exactly one bit differs between each pair of successive elements. There +are multiple Gray codings. An n-bit Gray code corresponds to a +Hamiltonian cycle on an n-dimensional hypercube. + +@noindent +Gray codes find use communicating incrementally changing values between +asynchronous agents. De-laminated Gray codes comprise the coordinates +of Hilbert space-filling curves. + + +@defun integer->gray-code k +Converts @var{k} to a Gray code of the same @code{integer-length} as +@var{k}. + +@defunx gray-code->integer k +Converts the Gray code @var{k} to an integer of the same +@code{integer-length} as @var{k}. + +For any non-negative integer @var{k}, +@example +(eqv? k (gray-code->integer (integer->gray-code k))) +@end example +@end defun + +@defun = k1 k2 +@defunx gray-code<? k1 k2 +@defunx gray-code>? k1 k2 +@defunx gray-code<=? k1 k2 +@defunx gray-code>=? k1 k2 +These procedures return #t if their Gray code arguments are +(respectively): equal, monotonically increasing, monotonically +decreasing, monotonically nondecreasing, or monotonically nonincreasing. + +For any non-negative integers @var{k1} and @var{k2}, the Gray code +predicate of @code{(integer->gray-code k1)} and +@code{(integer->gray-code k2)} will return the same value as the +corresponding predicate of @var{k1} and @var{k2}. +@end defun + +@subsubsection Bitwise Lamination +@cindex lamination + + +@defun bitwise-laminate k1 @dots{} +@defunx bitwise-delaminate count k + +Returns an integer composed of the bits of @var{k1} @dots{} interlaced +in argument order. Given @var{k1}, @dots{} @var{kn}, the n low-order +bits of the returned value will be the lowest-order bit of each +argument. + + +@defunx bitwise-laminate count k +Returns a list of @var{count} integers comprised of every @var{count}h +bit of the integer @var{k}. + +@example +(map (lambda (k) (number->string k 2)) + (bitwise-delaminate 4 #x7654)) + @result{} ("0" "1111" "1100" "1010") +(number->string (bitwise-laminate 0 #b1111 #b1100 #b1010) 16) + @result{} "7654" +@end example + +For any non-negative integers @var{k} and @var{count}: +@example +(eqv? k (bitwise-laminate (bitwise-delaminate count k))) +@end example +@end defun + + +@defun delaminate-list count ks + + +Returns a list of @var{count} integers comprised of the @var{j}th +bit of the integers @var{ks} where @var{j} ranges from @var{count}-1 +to 0. + +@example +(map (lambda (k) (number->string k 2)) + (delaminate-list 4 '(7 6 5 4 0 0 0 0))) + @result{} ("0" "11110000" "11000000" "10100000") +@end example + +@code{delaminate-list} is its own inverse: +@example +(delaminate-list 8 (delaminate-list 4 '(7 6 5 4 0 0 0 0))) + @result{} (7 6 5 4 0 0 0 0) +@end example +@end defun + |