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, 10 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 6c51292b..44ef6b0e 100644
--- a/lib.c
+++ b/lib.c
@@ -4025,6 +4025,11 @@ val chr_iscntrl(val ch)
 
 val chr_isdigit(val ch)
 {
+  return if2(iswdigit(c_chr(ch)), t);
+}
+
+val chr_digit(val ch)
+{
   return if2(iswdigit(c_chr(ch)), minus(ch, chr('0')));
 }
 
@@ -4070,6 +4075,11 @@ val chr_isupper(val ch)
 
 val chr_isxdigit(val ch)
 {
+  return tnil(iswxdigit(c_chr(ch)));
+}
+
+val chr_xdigit(val ch)
+{
   wchar_t cc = c_chr(ch);
 
   if ('0' <= cc && cc <= '9')