<s>
Berkeley	B-Language
Yacc	I-Language
(	O
byacc	B-Language
)	O
is	O
a	O
Unix	B-Application
parser	B-Language
generator	I-Language
designed	O
to	O
be	O
compatible	O
with	O
Yacc	B-Application
.	O
</s>
<s>
Due	O
to	O
its	O
liberal	O
license	O
and	O
because	O
it	O
was	O
faster	O
than	O
the	O
AT&T	O
Yacc	B-Application
,	O
it	O
quickly	O
became	O
the	O
most	O
popular	O
version	O
of	O
Yacc	B-Application
.	O
</s>
<s>
It	O
contains	O
features	O
not	O
available	O
in	O
Yacc	B-Application
,	O
such	O
as	O
reentrancy	O
,	O
which	O
is	O
implemented	O
in	O
a	O
way	O
that	O
is	O
broadly	O
compatible	O
with	O
GNU	B-Application
Bison	I-Application
.	O
</s>
<s>
In	O
1985	O
,	O
Robert	O
Corbett	O
developed	O
an	O
original	O
LALR	B-Application
parser	I-Application
generator	I-Application
based	O
on	O
a	O
1982	O
paper	O
by	O
DeRemer	O
and	O
Pennello	O
.	O
</s>
<s>
It	O
was	O
originally	O
named	O
Byson	O
and	O
was	O
incompatible	O
with	O
Yacc	B-Application
but	O
it	O
was	O
subsequently	O
renamed	O
Bison	B-Application
and	O
became	O
the	O
basis	O
of	O
GNU	B-Application
Bison	I-Application
.	O
</s>
<s>
Later	O
in	O
1985	O
,	O
Corbett	O
developed	O
his	O
LALR	B-Application
parser	I-Application
generator	I-Application
,	O
making	O
it	O
Yacc-compatible	O
and	O
naming	O
it	O
Zeus	O
but	O
subsequently	O
renaming	O
it	O
Zoo	O
.	O
</s>
<s>
Corbett	O
published	O
the	O
source	O
code	O
for	O
Zoo	O
in	O
a	O
Usenet	B-Application
newsgroup	I-Application
but	O
it	O
went	O
mostly	O
unnoticed	O
until	O
later	O
in	O
September	O
1989	O
when	O
Corbett	O
posted	O
on	O
the	O
comp.compilers	O
newsgroup	B-Application
about	O
putting	O
the	O
source	O
code	O
on	O
an	O
FTP	B-Protocol
server	I-Protocol
.	O
</s>
<s>
There	O
was	O
discussion	O
about	O
renaming	O
it	O
and	O
by	O
October	O
1989	O
it	O
had	O
become	O
known	O
as	O
Berkeley	B-Language
Yacc	I-Language
(	O
byacc	B-Language
)	O
.	O
</s>
<s>
In	O
1995	O
,	O
Chris	O
Dodd	O
developed	O
BtYacc	O
,	O
a	O
backtracking	B-Algorithm
derivative	O
of	O
Berkeley	B-Language
Yacc	I-Language
to	O
support	O
parsing	O
context-sensitive	O
languages	O
like	O
C++	B-Language
,	O
based	O
on	O
a	O
1993	O
paper	O
by	O
Merrill	O
describing	O
similar	O
modifications	O
to	O
AT&T	O
Yacc	B-Application
.	O
</s>
<s>
Its	O
backtracking	B-Algorithm
and	O
semantic	O
disambiguation	O
capabilities	O
allows	O
it	O
to	O
generator	O
parsers	O
for	O
ambiguous	O
grammars	O
.	O
</s>
<s>
In	O
1997	O
,	O
Vadim	O
Maslov	O
took	O
over	O
maintenance	O
of	O
BtYacc	O
to	O
support	O
a	O
COBOL	B-Application
parser	O
developed	O
by	O
his	O
company	O
.	O
</s>
<s>
By	O
1999	O
,	O
the	O
last	O
3.0	O
release	O
,	O
had	O
been	O
converted	O
to	O
C++	B-Language
,	O
making	O
it	O
no	O
longer	O
implemented	O
in	O
C	B-Language
.	O
</s>
<s>
In	O
2000	O
,	O
Thomas	O
E	O
.	O
Dickey	O
ported	O
Berkeley	B-Language
Yacc	I-Language
to	O
OpenVMS	B-Operating_System
to	O
facilitate	O
porting	O
tin	B-Protocol
to	O
VMS	B-Operating_System
.	O
</s>
<s>
After	O
failing	O
to	O
find	O
another	O
maintainer	O
,	O
Dickey	O
has	O
maintained	O
Berkeley	B-Language
Yacc	I-Language
since	O
February	O
2002	O
.	O
</s>
<s>
A	O
significant	O
update	O
was	O
the	O
conversion	O
from	O
K&R	O
C	B-Language
to	O
ANSI	O
C89	O
.	O
</s>
<s>
In	O
2014	O
,	O
Tom	O
Shields	O
integrated	O
BtYacc	O
backtracking	B-Algorithm
into	O
Berkeley	B-Language
Yacc	I-Language
effectively	O
subsuming	O
BtYacc	O
and	O
again	O
supporting	O
C	B-Language
(	O
instead	O
of	O
only	O
C++	B-Language
)	O
in	O
Dickey	O
releases	O
since	O
April	O
2014	O
.	O
</s>
<s>
Parser	B-Language
generators	I-Language
typically	O
deal	O
with	O
three	O
languages	O
:	O
the	O
language	O
a	O
generator	O
is	O
implemented	O
in	O
,	O
the	O
language	O
a	O
generated	O
parser	O
is	O
implemented	O
in	O
and	O
of	O
course	O
the	O
metalanguage	O
that	O
describes	O
whatever	O
a	O
generated	O
parser	O
should	O
parse	O
.	O
</s>
<s>
A	O
fourth	O
language	O
could	O
be	O
considered	O
whatever	O
language	O
a	O
generated	O
parser	O
parses	O
but	O
parser	B-Language
generators	I-Language
do	O
not	O
handle	O
such	O
directly	O
,	O
instead	O
just	O
focusing	O
on	O
generating	O
a	O
parser	O
from	O
a	O
given	O
description	O
while	O
letting	O
the	O
generated	O
parser	O
deal	O
with	O
such	O
.	O
</s>
<s>
Yacc	B-Application
is	O
written	O
in	O
C	B-Language
and	O
generates	O
parsers	O
in	O
C	B-Language
from	O
its	O
own	O
Yacc	B-Application
metalanguage	O
descriptions	O
.	O
</s>
<s>
This	O
is	O
also	O
how	O
Berkely	O
Yacc	B-Application
works	O
(	O
thus	O
its	O
compatibility	O
)	O
,	O
however	O
,	O
a	O
number	O
of	O
derivatives	O
have	O
been	O
created	O
to	O
allow	O
it	O
to	O
generate	O
parsers	O
in	O
languages	O
other	O
than	O
C	B-Language
.	O
</s>
<s>
Ray	O
Lischner	O
developed	O
perl-byacc	O
(	O
pbyacc	O
)	O
from	O
byacc	B-Language
1.6	O
,	O
so	O
that	O
it	O
could	O
also	O
generate	O
parsers	O
in	O
Perl	B-Language
.	O
</s>
<s>
Later	O
Richard	O
"	O
Rick	O
"	O
Ohnemus	O
ported	O
the	O
patches	O
from	O
byacc	B-Language
1.6	O
to	O
byacc	B-Language
1.8	O
.	O
</s>
<s>
And	O
later	O
in	O
1996	O
,	O
Jake	O
Donham	O
developed	O
p5yacc	O
from	O
perl-yacc	O
1.8.2	O
so	O
that	O
its	O
generated	O
Perl	B-Language
parsers	O
would	O
use	O
Perl	B-Language
5	O
classes	O
.	O
</s>
<s>
In	O
1997	O
,	O
Bob	O
Jamison	O
developed	O
BYACC/Java	O
(	O
later	O
called	O
BYACC/J	O
or	O
byaccj	O
)	O
from	O
byacc	B-Language
1.8	O
,	O
so	O
that	O
it	O
could	O
also	O
generate	O
parsers	O
in	O
Java	B-Language
.	O
</s>
<s>
In	O
2000	O
,	O
Bruce	O
Bahnsen	O
merged	O
in	O
the	O
Java	B-Language
parser	O
capabilities	O
of	O
BYACC/J	O
into	O
perl-yacc	O
and	O
added	O
the	O
ability	O
to	O
generate	O
parsers	O
in	O
Python	B-Language
.	O
</s>
<s>
In	O
2003	O
,	O
Dave	O
Bodenstab	O
merged	O
tyacc	O
and	O
p5yacc	O
to	O
develop	O
a	O
PERL-TCL-YACC	O
rebasing	O
it	O
from	O
4.8	O
release	O
of	O
yacc	B-Application
from	O
FreeBSD	B-Operating_System
(	O
a	O
byacc	B-Language
derivative	O
)	O
.	O
</s>
