Fix match-regex not conforming to documentation.

The documentation says that match-regex returns the length.
Actually, it returns the position after the last character
matched. This makes a difference when the match doesn't begin
at character zero.

The actual behavior is that of the match_regex C function
which has behaved that way since the dawn of TXR, and
internals depend on it behaving that way.

So the internal function is being retained, and a new function
is being registered as the match-regex intrinsic.  The choice
of binding for match-regex is subject to the compatibility
option.

The behavior of match-regst is also being fixed since its
return value is incorrect due to this issue. Since its
return value makes no sense at all (does not represent
the matched text), it is not subject to the compatibility
option; it is just fixed to conform with the documentation.

* regex.c (match_regex_len): New function.
(match_regst): Keep using match_regex, but use its return
value properly. This simplifies the range extraction code,
which is why match_regex works that way in the first place.
(regex_init): Register match-regex to match_regex_len,
unless compatibility <= 150 is requested; then register
to match_regex.

* regex.h (match_regex_len): Declared.

* txr.1: Compatibility notes added.

1 files changed, 1 insertions, 0 deletions

diff --git a/regex.h b/regex.h
index 599e985e..80494860 100644
--- a/regex.h
+++ b/regex.h
@@ -34,6 +34,7 @@ val regexp(val);
 val search_regex(val haystack, val needle_regex, val start_num, val from_end);
 val range_regex(val haystack, val needle_regex, val start_num, val from_end);
 val match_regex(val str, val regex, val pos);
+val match_regex_len(val str, val regex, val pos);
 val match_regex_right(val str, val regex, val end);
 val search_regst(val haystack, val needle_regex, val start_num, val from_end);
 val match_regst(val str, val regex, val pos);