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/eval.c b/eval.c
index 2fd252e1..478b1345 100644
--- a/eval.c
+++ b/eval.c
@@ -7787,6 +7787,8 @@ void eval_init(void)
   reg_fun(intern(lit("ssort"), user_package), func_n3o(ssort, 1));
   reg_fun(intern(lit("nshuffle"), user_package), func_n2o(nshuffle, 1));
   reg_fun(intern(lit("shuffle"), user_package), func_n2o(shuffle, 1));
+  reg_fun(intern(lit("cnshuffle"), user_package), func_n2o(cnshuffle, 1));
+  reg_fun(intern(lit("cshuffle"), user_package), func_n2o(cshuffle, 1));
   reg_fun(intern(lit("find"), user_package), func_n4o(find, 2));
   reg_fun(intern(lit("rfind"), user_package), func_n4o(rfind, 2));
   reg_fun(intern(lit("find-if"), user_package), func_n3o(find_if, 2));