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/lib.h b/lib.h
index cc8ef265..0872c089 100644
--- a/lib.h
+++ b/lib.h
@@ -717,6 +717,7 @@ val chr_isalpha(val ch);
 val chr_isascii(val ch);
 val chr_iscntrl(val ch);
 val chr_isdigit(val ch);
+val chr_digit(val ch);
 val chr_isgraph(val ch);
 val chr_islower(val ch);
 val chr_isprint(val ch);
@@ -726,6 +727,7 @@ val chr_isblank(val ch);
 val chr_isunisp(val ch);
 val chr_isupper(val ch);
 val chr_isxdigit(val ch);
+val chr_xdigit(val ch);
 val chr_toupper(val ch);
 val chr_tolower(val ch);
 val int_chr(val ch);