Revert chr-isdigit/isxdigit, provide new functions.

It was a mistake to change the semantics of the return value
of chr-isdigit and chr-isdigit. It breaks code like
[partition-by chr-isdigit ...].  The behavior of chr-isdigit
and chr-isxdigit is restored to returning t and nil. New
chr-digit and chr-xdigit functions are introduced for
returning the digit value or nil.

* eval.c (eval_init): Register chr-digit and chr-xdigit
intrinsics.

* lib.c (chr_isdigit, chr_isxdigit): Restore old behavior.
(chr_digit, chr_xdigit): New functions.

* lib.h (chr_digit, chr_xdigit): Declared.

* txr.1: Everything documented.

1 files changed, 2 insertions, 0 deletions

diff --git a/eval.c b/eval.c
index 438d8476..cbc5e89b 100644
--- a/eval.c
+++ b/eval.c
@@ -5024,6 +5024,7 @@ void eval_init(void)
   reg_fun(intern(lit("chr-isascii"), user_package), func_n1(chr_isascii));
   reg_fun(intern(lit("chr-iscntrl"), user_package), func_n1(chr_iscntrl));
   reg_fun(intern(lit("chr-isdigit"), user_package), func_n1(chr_isdigit));
+  reg_fun(intern(lit("chr-digit"), user_package), func_n1(chr_digit));
   reg_fun(intern(lit("chr-isgraph"), user_package), func_n1(chr_isgraph));
   reg_fun(intern(lit("chr-islower"), user_package), func_n1(chr_islower));
   reg_fun(intern(lit("chr-isprint"), user_package), func_n1(chr_isprint));
@@ -5033,6 +5034,7 @@ void eval_init(void)
   reg_fun(intern(lit("chr-isunisp"), user_package), func_n1(chr_isunisp));
   reg_fun(intern(lit("chr-isupper"), user_package), func_n1(chr_isupper));
   reg_fun(intern(lit("chr-isxdigit"), user_package), func_n1(chr_isxdigit));
+  reg_fun(intern(lit("chr-xdigit"), user_package), func_n1(chr_xdigit));
   reg_fun(intern(lit("chr-toupper"), user_package), func_n1(chr_toupper));
   reg_fun(intern(lit("chr-tolower"), user_package), func_n1(chr_tolower));
   {