New functions: cshuffle and cnshuffle.

These functions find random cyclic permutations.

* eval.c (eval_init): Register cshuffle and cnshuffle
intrinsics.

* lib.c (nshuffle_impl): New static function, formed out of
nshuffle.
(nhuffle): Now wrapper around nshuffle_impl.
(shuffle): Also wraps nshuffle_impl rather than nshuffle.
(cnshuffle, cshuffle): New funtions.

* lib.h (cnshuffle, cshuffle): Declared.

* txr.1: Documented new functions. Also added warning
about limitations on permutation reachability in relation
to PRNG state size.

1 files changed, 2 insertions, 0 deletions

diff --git a/lib.h b/lib.h
index 0c300e8a..f83d59b0 100644
--- a/lib.h
+++ b/lib.h
@@ -1384,6 +1384,8 @@ val snsort(val seq, val lessfun, val keyfun);
 val ssort(val seq, val lessfun, val keyfun);
 val nshuffle(val seq, val randstate);
 val shuffle(val seq, val randstate);
+val cnshuffle(val seq, val randstate);
+val cshuffle(val seq, val randstate);
 val multi_sort(val lists, val funcs, val key_funcs);
 val sort_group(val seq, val keyfun, val lessfun);
 val unique(val seq, val keyfun, varg hashv_args);