<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
scannerless	B-Application
parsing	I-Application
(	O
also	O
called	O
lexerless	B-Application
parsing	I-Application
)	O
performs	O
tokenization	O
(	O
breaking	O
a	O
stream	O
of	O
characters	O
into	O
words	O
)	O
and	O
parsing	O
(	O
arranging	O
the	O
words	O
into	O
phrases	O
)	O
in	O
a	O
single	O
step	O
,	O
rather	O
than	O
breaking	O
it	O
up	O
into	O
a	O
pipeline	B-Operating_System
of	O
a	O
lexer	B-Application
followed	O
by	O
a	O
parser	B-Language
,	O
executing	O
concurrently	B-Architecture
.	O
</s>
<s>
A	O
language	O
grammar	O
is	O
scannerless	O
if	O
it	O
uses	O
a	O
single	O
formalism	O
to	O
express	O
both	O
the	O
lexical	B-Application
(	O
word	O
level	O
)	O
and	O
phrase	O
level	O
structure	O
of	O
the	O
language	O
.	O
</s>
<s>
Dividing	O
processing	O
into	O
a	O
lexer	B-Application
followed	O
by	O
a	O
parser	B-Language
is	O
more	O
modular	O
;	O
scannerless	B-Application
parsing	I-Application
is	O
primarily	O
used	O
when	O
a	O
clear	O
lexer	B-Application
–	O
parser	B-Language
distinction	O
is	O
unneeded	O
or	O
unwanted	O
.	O
</s>
<s>
Examples	O
of	O
when	O
this	O
is	O
appropriate	O
include	O
TeX	B-Application
,	O
most	O
wiki	B-Protocol
grammars	O
,	O
makefiles	O
,	O
simple	O
application-specific	O
scripting	B-Language
languages	I-Language
,	O
and	O
Raku	B-Application
.	O
</s>
<s>
Since	O
the	O
lexical	B-Application
scanning	O
and	O
syntactic	O
parsing	O
are	O
combined	O
,	O
the	O
resulting	O
parser	B-Language
tends	O
to	O
be	O
more	O
complicated	O
and	O
thus	O
harder	O
to	O
understand	O
and	O
debug	O
.	O
</s>
<s>
The	O
same	O
will	O
hold	O
for	O
the	O
associated	O
grammar	O
,	O
if	O
a	O
grammar	O
is	O
used	O
to	O
generate	O
the	O
parser	B-Language
.	O
</s>
<s>
The	O
resulting	O
parser	B-Language
tends	O
to	O
be	O
significantly	O
less	O
efficient	O
than	O
a	O
lexer-parser	O
pipeline	B-Operating_System
with	O
regard	O
to	O
both	O
time	O
and	O
memory	O
.	O
</s>
<s>
is	O
a	O
parser	B-Language
for	O
the	O
modular	B-Application
Syntax	I-Application
Definition	I-Application
Formalism	I-Application
SDF	B-Application
,	O
and	O
is	O
part	O
of	O
the	O
ASF+SDF	O
Meta-Environment	O
and	O
the	O
Stratego/XT	O
program	O
transformation	O
system	O
.	O
</s>
<s>
,	O
a	O
pure	O
Java	O
implementation	O
of	O
SGLR	O
,	O
also	O
based	O
on	O
SDF	B-Application
.	O
</s>
<s>
TXL	B-Language
supports	O
character-level	O
parsing	O
.	O
</s>
<s>
generates	O
ANSI	O
C	B-Language
code	O
for	O
scannerless	O
GLR	B-Application
parsers	I-Application
.	O
</s>
<s>
Spirit	B-General_Concept
allows	O
for	O
both	O
scannerless	O
and	O
scanner-based	O
parsing	O
.	O
</s>
<s>
SBP	B-Language
is	O
a	O
scannerless	B-Application
parser	I-Application
for	O
boolean	O
grammars	O
(	O
a	O
superset	O
of	O
context-free	O
grammars	O
)	O
,	O
written	O
in	O
Java	O
.	O
</s>
<s>
is	O
a	O
two	O
phase	O
scannerless	B-Application
parser	I-Application
generator	O
with	O
support	O
for	O
mapping	O
the	O
grammar	O
rules	O
into	O
objects	O
,	O
written	O
in	O
Java	O
.	O
</s>
<s>
The	O
Raku	B-Application
Grammars	O
feature	O
of	O
the	O
general	O
purpose	O
programming	O
language	O
Raku	B-Application
.	O
</s>
<s>
is	O
a	O
scannerless	B-Application
parser	I-Application
written	O
in	O
pure	O
Python	O
.	O
</s>
<s>
META	B-Application
II	I-Application
Has	O
built	O
in	O
token	O
parsers	B-Language
functions	O
.	O
</s>
<s>
TREE-META	B-Application
Like	O
META	B-Application
II	I-Application
also	O
is	O
scannerless	O
having	O
builtin	O
lexer	B-Application
functions	O
.	O
</s>
