<s>
In	O
computer-based	O
language	O
recognition	O
,	O
ANTLR	B-Application
(	O
pronounced	O
antler	O
)	O
,	O
or	O
ANother	O
Tool	O
for	O
Language	O
Recognition	O
,	O
is	O
a	O
parser	B-Language
generator	I-Language
that	O
uses	O
a	O
LL( *	O
)	O
algorithm	O
for	O
parsing	O
.	O
</s>
<s>
ANTLR	B-Application
is	O
the	O
successor	O
to	O
the	O
Purdue	O
Compiler	O
Construction	O
Tool	O
Set	O
(	O
PCCTS	O
)	O
,	O
first	O
developed	O
in	O
1989	O
,	O
and	O
is	O
under	O
active	O
development	O
.	O
</s>
<s>
ANTLR	B-Application
takes	O
as	O
input	O
a	O
grammar	O
that	O
specifies	O
a	O
language	O
and	O
generates	O
as	O
output	O
source	O
code	O
for	O
a	O
recognizer	O
of	O
that	O
language	O
.	O
</s>
<s>
Ada95	B-Language
,	O
</s>
<s>
ActionScript	B-Operating_System
,	O
</s>
<s>
C	B-Language
,	O
</s>
<s>
C#	B-Application
,	O
</s>
<s>
Java	B-Language
,	O
</s>
<s>
JavaScript	B-Language
,	O
</s>
<s>
Objective-C	B-Language
,	O
</s>
<s>
Perl	B-Language
,	O
</s>
<s>
Python	B-Language
,	O
</s>
<s>
C#	B-Application
,	O
</s>
<s>
C++	O
,	O
</s>
<s>
Java	B-Language
,	O
</s>
<s>
JavaScript	B-Language
,	O
</s>
<s>
Go	B-Application
,	O
</s>
<s>
PHP	B-Application
,	O
</s>
<s>
Python	B-Language
(	O
2	O
and	O
3	O
)	O
,	O
</s>
<s>
and	O
Swift	B-Application
.	O
</s>
<s>
ANTLR	B-Application
can	O
generate	O
lexers	B-Application
,	O
parsers	B-Language
,	O
tree	O
parsers	B-Language
,	O
and	O
combined	O
lexer-parsers	B-Application
.	O
</s>
<s>
Parsers	B-Language
can	O
automatically	O
generate	O
parse	O
trees	O
or	O
abstract	B-Data_Structure
syntax	I-Data_Structure
trees	I-Data_Structure
,	O
which	O
can	O
be	O
further	O
processed	O
with	O
tree	O
parsers	B-Language
.	O
</s>
<s>
ANTLR	B-Application
provides	O
a	O
single	O
consistent	O
notation	O
for	O
specifying	O
lexers	B-Application
,	O
parsers	B-Language
,	O
and	O
tree	O
parsers	B-Language
.	O
</s>
<s>
By	O
default	O
,	O
ANTLR	B-Application
reads	O
a	O
grammar	O
and	O
generates	O
a	O
recognizer	O
for	O
the	O
language	O
defined	O
by	O
the	O
grammar	O
(	O
i.e.	O
,	O
a	O
program	O
that	O
reads	O
an	O
input	O
stream	O
and	O
generates	O
an	O
error	O
if	O
the	O
input	O
stream	O
does	O
not	O
conform	O
to	O
the	O
syntax	O
specified	O
by	O
the	O
grammar	O
)	O
.	O
</s>
<s>
Other	O
than	O
lexers	B-Application
and	O
parsers	B-Language
,	O
ANTLR	B-Application
can	O
be	O
used	O
to	O
generate	O
tree	O
parsers	B-Language
.	O
</s>
<s>
These	O
are	O
recognizers	O
that	O
process	O
abstract	B-Data_Structure
syntax	I-Data_Structure
trees	I-Data_Structure
,	O
which	O
can	O
be	O
automatically	O
generated	O
by	O
parsers	B-Language
.	O
</s>
<s>
These	O
tree	O
parsers	B-Language
are	O
unique	O
to	O
ANTLR	B-Application
and	O
help	O
processing	B-Application
abstract	B-Data_Structure
syntax	I-Data_Structure
trees	I-Data_Structure
.	O
</s>
<s>
and	O
ANTLR	B-Application
4	O
are	O
free	B-Application
software	I-Application
,	O
published	O
under	O
a	O
three-clause	O
BSD	B-Operating_System
License	I-Operating_System
.	O
</s>
<s>
Prior	O
versions	O
were	O
released	O
as	O
public	B-Application
domain	I-Application
software	I-Application
.	O
</s>
<s>
Documentation	O
,	O
derived	O
from	O
Parr	O
's	O
book	O
The	O
Definitive	O
ANTLR	B-Application
4	O
Reference	O
,	O
is	O
included	O
with	O
the	O
BSD-licensed	O
ANTLR	B-Application
4	O
source	O
.	O
</s>
<s>
Various	O
plugins	O
have	O
been	O
developed	O
for	O
the	O
Eclipse	B-Application
development	I-Application
environment	I-Application
to	O
support	O
the	O
ANTLR	B-Application
grammar	O
,	O
including	O
ANTLR	B-Application
Studio	I-Application
,	O
a	O
proprietary	B-Application
product	I-Application
,	O
as	O
well	O
as	O
the	O
"	O
ANTLR	B-Application
2	O
"	O
and	O
"	O
ANTLR	B-Application
3	O
"	O
plugins	O
for	O
Eclipse	B-Application
hosted	O
on	O
SourceForge	B-Application
.	O
</s>
<s>
ANTLR	B-Application
4	O
deals	O
with	O
direct	O
left	B-Application
recursion	I-Application
correctly	O
,	O
but	O
not	O
with	O
left	B-Application
recursion	I-Application
in	O
general	O
,	O
i.e.	O
,	O
grammar	O
rules	O
x	O
that	O
refer	O
to	O
y	O
that	O
refer	O
to	O
x	O
.	O
</s>
<s>
As	O
reported	O
on	O
the	O
tools	O
page	O
of	O
the	O
ANTLR	B-Application
project	O
,	O
plug-ins	O
that	O
enable	O
features	O
like	O
syntax	O
highlighting	O
,	O
syntax	O
error	O
checking	O
and	O
code	O
completion	O
are	O
freely	O
available	O
for	O
the	O
most	O
common	O
IDEs	O
(	O
Intellij	B-Language
IDEA	I-Language
,	O
NetBeans	B-Application
,	O
Eclipse	B-Application
,	O
Visual	B-Application
Studio	I-Application
and	O
Visual	B-Language
Studio	I-Language
Code	I-Language
)	O
.	O
</s>
<s>
Software	O
built	O
using	O
ANTLR	B-Application
includes	O
:	O
</s>
<s>
Groovy	B-Application
.	O
</s>
<s>
Jython	B-Language
.	O
</s>
<s>
OpenJDK	O
Compiler	O
Grammar	O
project	O
experimental	O
version	O
of	O
the	O
javac	B-General_Concept
compiler	O
based	O
upon	O
a	O
grammar	O
written	O
in	O
ANTLR	B-Application
.	O
</s>
<s>
Apex	O
,	O
com	O
's	O
programming	O
language	O
.	O
</s>
<s>
The	O
expression	O
evaluator	O
in	O
Numbers	B-Operating_System
,	O
Apple	O
's	O
spreadsheet	O
.	O
</s>
<s>
Twitter	B-Application
's	O
search	O
query	O
language	O
.	O
</s>
<s>
Apache	B-Application
Cassandra	I-Application
.	O
</s>
<s>
Processing	B-Application
.	O
</s>
<s>
JabRef	B-Language
.	O
</s>
<s>
Over	O
200	O
grammars	O
implemented	O
in	O
ANTLR	B-Application
4	O
are	O
available	O
on	O
GitHub	B-Application
.	O
</s>
<s>
They	O
range	O
from	O
grammars	O
for	O
a	O
URL	O
to	O
grammars	O
for	O
entire	O
languages	O
like	O
C	B-Language
,	O
Java	B-Language
and	O
Go	B-Application
.	O
</s>
<s>
In	O
the	O
following	O
example	O
,	O
a	O
parser	B-Language
in	O
ANTLR	B-Application
describes	O
the	O
sum	O
of	O
expressions	O
can	O
be	O
seen	O
in	O
the	O
form	O
of	O
"	O
1	O
+	O
2	O
+	O
3	O
"	O
:	O
</s>
<s>
The	O
following	O
listing	O
demonstrates	O
the	O
call	O
of	O
the	O
parser	B-Language
in	O
a	O
program	O
:	O
</s>
