<s>
Racket	O
is	O
a	O
general-purpose	B-Language
,	O
multi-paradigm	O
programming	O
language	O
and	O
a	O
multi-platform	B-Operating_System
distribution	O
that	O
includes	O
the	O
Racket	O
language	O
,	O
compiler	B-Language
,	O
large	O
standard	O
library	O
,	O
IDE	B-Application
,	O
development	O
tools	O
,	O
and	O
a	O
set	O
of	O
additional	O
languages	O
including	O
Typed	O
Racket	O
(	O
a	O
sister	O
language	O
of	O
Racket	O
with	O
a	O
static	O
type-checker	O
)	O
,	O
Swindle	O
,	O
FrTime	O
,	O
Lazy	O
Racket	O
,	O
R5RS	B-Language
&	O
R6RS	O
Scheme	B-Language
,	O
Scribble	O
,	O
Datalog	O
,	O
Racklog	O
,	O
Algol	B-Language
60	I-Language
and	O
several	O
teaching	O
languages	O
.	O
</s>
<s>
The	O
Racket	O
language	O
is	O
a	O
modern	O
dialect	O
of	O
Lisp	B-Language
and	O
a	O
descendant	O
of	O
Scheme	B-Language
.	O
</s>
<s>
Racket	O
is	O
also	O
used	O
for	O
scripting	B-Language
,	O
computer	B-General_Concept
science	I-General_Concept
education	O
,	O
and	O
research	O
.	O
</s>
<s>
The	O
Racket	O
platform	O
provides	O
an	O
implementation	O
of	O
the	O
Racket	O
language	O
(	O
including	O
a	O
runtime	B-Device
system	I-Device
,	O
libraries	O
,	O
and	O
compiler	B-Language
supporting	O
several	O
compilation	B-Language
modes	O
:	O
machine	O
code	O
,	O
machine-independent	B-Operating_System
,	O
interpreted	O
,	O
and	O
JIT	O
)	O
along	O
with	O
the	O
DrRacket	O
integrated	B-Application
development	I-Application
environment	I-Application
(	O
IDE	B-Application
)	O
written	O
in	O
Racket	O
.	O
</s>
<s>
Racket	O
is	O
used	O
by	O
the	O
ProgramByDesign	B-Language
outreach	O
program	O
,	O
which	O
aims	O
to	O
turn	O
computer	B-General_Concept
science	I-General_Concept
into	O
"	O
an	O
indispensable	O
part	O
of	O
the	O
liberal	O
arts	O
curriculum	O
"	O
.	O
</s>
<s>
The	O
core	O
Racket	O
language	O
is	O
known	O
for	O
its	O
extensive	O
macro	O
system	O
which	O
enables	O
creating	O
embedded	O
and	O
domain-specific	B-Language
languages	I-Language
,	O
language	O
constructs	O
such	O
as	O
classes	O
or	O
modules	B-Architecture
,	O
and	O
separate	O
dialects	O
of	O
Racket	O
with	O
different	O
semantics	B-Application
.	O
</s>
<s>
The	O
platform	O
distribution	O
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
distributed	O
under	O
the	O
Apache	B-Application
2.0	I-Application
and	O
MIT	B-License
licenses	I-License
.	O
</s>
<s>
Extensions	O
and	O
packages	O
written	O
by	O
the	O
community	O
may	O
be	O
uploaded	O
to	O
Racket	O
's	O
package	B-Application
catalog	I-Application
.	O
</s>
<s>
In	O
January	O
1995	O
,	O
the	O
group	O
decided	O
to	O
develop	O
a	O
pedagogic	O
programming	B-Application
environment	I-Application
based	O
on	O
Scheme	B-Language
.	O
</s>
<s>
Matthew	O
Flatt	O
cobbled	O
together	O
MrEd	O
,	O
the	O
original	O
virtual	B-Architecture
machine	I-Architecture
for	O
Racket	O
,	O
from	O
libscheme	O
,	O
wxWidgets	B-Language
,	O
and	O
a	O
few	O
other	O
free	O
systems	O
.	O
</s>
<s>
In	O
the	O
years	O
that	O
followed	O
,	O
a	O
team	O
including	O
Flatt	O
,	O
Robby	O
Findler	O
,	O
Shriram	O
Krishnamurthi	O
,	O
Cormac	O
Flanagan	O
,	O
and	O
many	O
others	O
produced	O
DrScheme	O
,	O
a	O
programming	B-Application
environment	I-Application
for	O
novice	O
Scheme	B-Language
programmers	O
and	O
a	O
research	O
environment	O
for	O
soft	O
typing	O
.	O
</s>
<s>
The	O
main	O
development	O
language	O
that	O
DrScheme	O
supported	O
was	O
named	O
PLT	O
Scheme	B-Language
.	O
</s>
<s>
In	O
parallel	O
,	O
the	O
team	O
began	O
conducting	O
workshops	O
for	O
high	O
school	O
teachers	O
,	O
training	O
them	O
in	O
program	O
design	O
and	O
functional	B-Language
programming	I-Language
.	O
</s>
<s>
Over	O
the	O
following	O
years	O
,	O
PLT	O
added	O
teaching	O
languages	O
,	O
an	O
algebraic	O
stepper	O
,	O
a	O
transparent	O
read	B-Application
–	I-Application
eval	I-Application
–	I-Application
print	I-Application
loop	I-Application
,	O
a	O
constructor-based	O
printer	O
,	O
and	O
many	O
other	O
innovations	O
to	O
DrScheme	O
,	O
producing	O
an	O
application-quality	O
pedagogic	O
program	B-Application
development	I-Application
environment	I-Application
.	O
</s>
<s>
The	O
first	O
generation	O
of	O
PLT	O
Scheme	B-Language
revisions	O
introduced	O
features	O
for	O
programming	O
in	O
the	O
large	O
with	O
both	O
modules	B-Architecture
and	O
classes	O
.	O
</s>
<s>
Version	O
42	O
introduced	O
units	O
–	O
a	O
first-class	O
module	B-Architecture
system	I-Architecture
–	O
to	O
complement	O
classes	O
for	O
large	O
scale	O
development	O
.	O
</s>
<s>
Java-style	O
interfaces	B-Application
)	O
and	O
also	O
lost	O
several	O
features	O
(	O
e.g.	O
</s>
<s>
multiple	B-Application
inheritance	I-Application
)	O
throughout	O
these	O
versions	O
.	O
</s>
<s>
The	O
next	O
major	O
revision	O
was	O
named	O
Version	O
200	O
,	O
which	O
introduced	O
a	O
new	O
default	O
module	B-Architecture
system	I-Architecture
that	O
cooperates	O
with	O
macros	O
.	O
</s>
<s>
In	O
particular	O
,	O
the	O
module	B-Architecture
system	I-Architecture
ensures	O
that	O
run-time	O
and	O
compile-time	B-Application
computation	O
are	O
separated	O
to	O
support	O
a	O
"	O
tower	O
of	O
languages	O
"	O
.	O
</s>
<s>
Unlike	O
units	O
,	O
these	O
modules	B-Architecture
are	O
not	O
first-class	O
objects	O
.	O
</s>
<s>
Version	O
300	O
introduced	O
Unicode	O
support	O
,	O
foreign	B-Application
library	I-Application
support	O
,	O
and	O
refinements	O
to	O
the	O
class	O
system	O
.	O
</s>
<s>
Later	O
on	O
,	O
the	O
300	O
series	O
improved	O
the	O
performance	O
of	O
the	O
language	O
runtime	O
with	O
an	O
addition	O
of	O
a	O
JIT	O
compiler	B-Language
and	O
a	O
switch	O
to	O
a	O
default	O
generational	O
garbage	O
collection	O
.	O
</s>
<s>
Version	O
4.0	O
introduced	O
the	O
#lang	O
shorthand	O
to	O
specify	O
the	O
language	O
that	O
a	O
module	B-Architecture
is	O
written	O
in	O
.	O
</s>
<s>
Further	O
,	O
the	O
revision	O
introduced	O
immutable	B-Application
pairs	O
and	O
lists	O
,	O
support	O
for	O
fine-grained	O
parallelism	B-Operating_System
,	O
and	O
a	O
statically-typed	O
dialect	O
.	O
</s>
<s>
On	O
7	O
June	O
2010	O
,	O
PLT	O
Scheme	B-Language
was	O
renamed	O
Racket	O
.	O
</s>
<s>
Subsequently	O
,	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
backend	O
was	O
rewritten	O
in	O
Racket	O
from	O
C++	B-Language
in	O
Version	O
5.1	O
using	O
native	O
UI	B-Library
toolkits	I-Library
on	O
all	O
platforms	O
.	O
</s>
<s>
Version	O
5.2	O
included	O
a	O
background	O
syntax	O
checking	O
tool	O
,	O
a	O
new	O
plotting	O
library	O
,	O
a	O
database	O
library	O
,	O
and	O
a	O
new	O
extended	O
REPL	B-Application
.	O
</s>
<s>
Version	O
5.3	O
included	O
a	O
new	O
submodule	O
feature	O
for	O
optionally	O
loaded	O
modules	B-Architecture
,	O
new	O
optimization	O
tools	O
,	O
a	O
JSON	B-General_Concept
library	O
,	O
and	O
other	O
features	O
.	O
</s>
<s>
In	O
version	O
6.0	O
,	O
Racket	O
released	O
its	O
second-generation	O
package	B-Application
management	I-Application
system	I-Application
.	O
</s>
<s>
Version	O
7	O
of	O
Racket	O
was	O
released	O
with	O
a	O
new	O
macro	O
expander	O
written	O
in	O
Racket	O
as	O
part	O
the	O
preparations	O
for	O
supporting	O
moving	O
to	O
the	O
Chez	B-Language
Scheme	I-Language
runtime	B-Device
system	I-Device
and	O
supporting	O
multiple	O
runtime	B-Device
systems	I-Device
.	O
</s>
<s>
They	O
use	O
now	O
either	O
the	O
Apache	B-Application
2.0	I-Application
license	I-Application
or	O
the	B-License
MIT	I-License
license	I-License
.	O
</s>
<s>
Racket	O
8.0	O
marks	O
the	O
first	O
release	O
where	O
Racket	O
with	O
the	O
Chez	B-Language
Scheme	I-Language
runtime	B-Device
system	I-Device
,	O
known	O
as	O
Racket	O
CS	O
,	O
is	O
the	O
default	O
implementation	O
.	O
</s>
<s>
Racket	O
's	O
core	O
language	O
includes	O
macros	O
,	O
modules	B-Architecture
,	O
lexical	B-Language
closures	I-Language
,	O
tail	B-Language
calls	I-Language
,	O
delimited	O
continuations	O
,	O
parameters	O
(	O
fluid	O
variables	O
)	O
,	O
software	B-Application
contracts	I-Application
,	O
green	B-Operating_System
threads	I-Operating_System
and	O
OS	B-Operating_System
threads	I-Operating_System
,	O
and	O
more	O
.	O
</s>
<s>
The	O
language	O
also	O
comes	O
with	O
primitives	O
,	O
such	O
as	O
eventspaces	O
and	O
custodians	O
,	O
which	O
control	O
resource	O
management	O
and	O
enables	O
the	O
language	O
to	O
act	O
like	O
an	O
operating	B-General_Concept
system	I-General_Concept
for	O
loading	O
and	O
managing	O
other	O
programs	O
.	O
</s>
<s>
Further	O
extensions	O
to	O
the	O
language	O
are	O
created	O
with	O
the	O
powerful	O
macro	O
system	O
,	O
which	O
together	O
with	O
the	O
module	B-Architecture
system	I-Architecture
and	O
custom	O
parsers	O
can	O
control	O
all	O
aspects	O
of	O
a	O
language	O
.	O
</s>
<s>
These	O
include	O
a	O
mixin	B-Language
class	I-Language
system	O
,	O
a	O
component	O
(	O
or	O
module	B-Architecture
)	O
system	O
as	O
expressive	O
as	O
opaque	O
ascription	O
in	O
the	O
ML	O
module	B-Architecture
system	I-Architecture
,	O
and	O
pattern	B-Language
matching	I-Language
.	O
</s>
<s>
Further	O
,	O
the	O
language	O
features	O
the	O
first	O
contract	O
system	O
for	O
a	O
higher-order	B-Application
programming	I-Application
language	O
.	O
</s>
<s>
Racket	O
's	O
contract	O
system	O
is	O
inspired	O
by	O
the	O
Design	B-Application
by	I-Application
Contract	I-Application
work	O
for	O
Eiffel	B-Language
and	O
extends	O
it	O
to	O
work	O
for	O
higher-order	O
values	O
such	O
as	O
first-class	B-Application
functions	I-Application
,	O
objects	O
,	O
reference	O
cells	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
Racket	O
includes	O
both	O
bytecode	O
and	O
JIT	O
(	O
JIT	O
)	O
compilers	B-Language
.	O
</s>
<s>
The	O
bytecode	O
compiler	B-Language
produces	O
an	O
internal	O
bytecode	O
format	O
run	O
by	O
the	O
Racket	O
virtual	B-Architecture
machine	I-Architecture
,	O
and	O
the	O
JIT	O
compiler	B-Language
translates	O
bytecode	O
to	O
machine	O
code	O
at	O
runtime	O
.	O
</s>
<s>
Since	O
2004	O
,	O
the	O
language	O
has	O
also	O
shipped	O
with	O
PLaneT	O
,	O
a	O
package	B-Application
manager	I-Application
that	O
is	O
integrated	O
into	O
the	O
module	B-Architecture
system	I-Architecture
so	O
that	O
third-party	B-General_Concept
libraries	I-General_Concept
can	O
be	O
transparently	O
imported	O
and	O
used	O
.	O
</s>
<s>
Also	O
,	O
PLaneT	O
has	O
a	O
built-in	O
versioning	O
policy	O
to	O
prevent	O
dependency	B-Protocol
hell	I-Protocol
.	O
</s>
<s>
The	O
features	O
that	O
most	O
clearly	O
distinguish	O
Racket	O
from	O
other	O
languages	O
in	O
the	O
Lisp	B-Language
family	O
are	O
its	O
integrated	O
language	O
extensibility	B-Application
features	O
that	O
support	O
building	O
new	O
domain-specific	B-Language
and	O
general-purpose	B-Language
languages	O
.	O
</s>
<s>
Racket	O
's	O
extensibility	B-Application
features	O
are	O
built	O
into	O
the	O
module	B-Architecture
system	I-Architecture
to	O
allow	O
context-sensitive	O
and	O
module-level	O
control	O
over	O
syntax	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
#%app	O
syntactic	O
form	O
can	O
be	O
overridden	O
to	O
change	O
the	O
semantics	B-Application
of	O
function	B-Algorithm
application	I-Algorithm
.	O
</s>
<s>
Similarly	O
,	O
the	O
#%	O
module-begin	O
form	O
allows	O
arbitrary	O
static	O
analysis	O
of	O
the	O
entire	O
module	B-Architecture
.	O
</s>
<s>
Since	O
any	O
module	B-Architecture
can	O
be	O
used	O
as	O
a	O
language	O
,	O
via	O
the	O
#lang	O
notation	O
,	O
this	O
effectively	O
means	O
that	O
virtually	O
any	O
aspect	O
of	O
the	O
language	O
can	O
be	O
programmed	O
and	O
controlled	O
.	O
</s>
<s>
The	O
module-level	O
extensibility	B-Application
features	O
are	O
combined	O
with	O
a	O
Scheme-like	O
hygienic	B-Application
macro	I-Application
system	O
,	O
which	O
provides	O
more	O
features	O
than	O
Lisp	B-Language
's	I-Language
s-expression	B-Protocol
manipulation	O
system	O
,	O
Scheme	B-Language
84	O
's	O
hygienic	B-Application
extend-syntax	O
macros	O
,	O
or	O
R5RS	B-Language
's	O
syntax-rules	B-Application
.	O
</s>
<s>
Indeed	O
,	O
it	O
is	O
fair	O
to	O
say	O
that	O
the	O
macro	O
system	O
is	O
a	O
carefully	O
tuned	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
for	O
compiler	B-Language
extensions	O
.	O
</s>
<s>
Using	O
this	O
compiler	B-Language
API	B-Application
,	O
programmers	O
can	O
add	O
features	O
and	O
entire	O
domain-specific	B-Language
languages	I-Language
in	O
a	O
manner	O
that	O
makes	O
them	O
completely	O
indistinguishable	O
from	O
built-in	O
language	O
constructs	O
.	O
</s>
<s>
Other	O
dialects	O
include	O
FrTime	O
(	O
functional	B-Application
reactive	I-Application
programming	I-Application
)	O
,	O
Scribble	O
(	O
documentation	O
language	O
)	O
,	O
Slideshow	O
(	O
presentation	O
language	O
)	O
,	O
and	O
several	O
languages	O
for	O
education	O
.	O
</s>
<s>
Such	O
languages	O
are	O
not	O
restricted	O
to	O
s-expression	B-Protocol
based	O
syntax	O
.	O
</s>
<s>
See	O
Racket	O
logic	B-Language
programming	I-Language
for	O
an	O
example	O
of	O
such	O
a	O
language	O
.	O
</s>
<s>
The	O
language	O
platform	O
provides	O
a	O
self-hosted	O
IDE	B-Application
named	O
DrRacket	O
,	O
a	O
continuation-based	O
web	B-Application
server	I-Application
,	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
,	O
and	O
other	O
tools	O
.	O
</s>
<s>
As	O
a	O
viable	O
scripting	B-Language
tool	O
with	O
libraries	O
like	O
common	O
scripting	B-Language
languages	I-Language
,	O
it	O
can	O
be	O
used	O
for	O
scripting	B-Language
the	O
Unix	B-Application
shell	O
.	O
</s>
<s>
DrRacket	O
(	O
formerly	O
DrScheme	O
)	O
is	O
widely	O
used	O
among	O
introductory	O
computer	B-General_Concept
science	I-General_Concept
courses	O
that	O
teach	O
Scheme	B-Language
or	O
Racket	O
and	O
is	O
lauded	O
for	O
its	O
simplicity	O
and	O
appeal	O
to	O
beginner	O
programmers	O
.	O
</s>
<s>
The	O
IDE	B-Application
was	O
originally	O
built	O
for	O
use	O
with	O
the	O
TeachScheme	B-Language
!	I-Language
</s>
<s>
project	O
(	O
now	O
ProgramByDesign	B-Language
)	O
,	O
an	O
outreach	O
effort	O
by	O
Northeastern	O
University	O
and	O
a	O
number	O
of	O
affiliated	O
universities	O
for	O
attracting	O
high	O
school	O
students	O
to	O
computer	B-General_Concept
science	I-General_Concept
courses	O
at	O
the	O
college	O
level	O
.	O
</s>
<s>
The	O
editor	O
provides	O
highlighting	O
for	O
syntax	O
and	O
run-time	O
errors	O
,	O
parenthesis	O
matching	O
,	O
a	O
debugger	B-Application
and	O
an	O
algebraic	O
stepper	O
.	O
</s>
<s>
Further	O
,	O
module-oriented	B-Architecture
programming	I-Architecture
is	O
supported	O
with	O
the	O
module	B-Architecture
browser	O
,	O
a	O
contour	O
view	O
,	O
integrated	O
testing	O
and	O
coverage	O
measurements	O
,	O
and	O
refactoring	O
support	O
.	O
</s>
<s>
DrRacket	O
is	O
available	O
for	O
Windows	B-Application
,	O
macOS	B-Application
,	O
Unix	B-Application
,	O
and	O
Linux	B-Application
with	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
and	O
programs	O
behave	O
similarly	O
on	O
all	O
these	O
platforms	O
.	O
</s>
<s>
Both	O
support	O
Linux	B-Application
,	O
Windows	B-Application
and	O
MacOS	B-Application
on	O
a	O
variety	O
of	O
architectures	O
and	O
are	O
supported	O
as	O
at	O
version	O
8.8	O
(	O
2023	O
)	O
.	O
</s>
<s>
The	O
default	O
implementation	O
uses	O
the	O
Chez	B-Language
Scheme	I-Language
incremental	O
compiler	B-Language
and	O
runtime	O
.	O
</s>
<s>
The	O
alternate	O
implementation	O
generates	O
platform-independent	B-Operating_System
bytecode	O
and	O
uses	O
Just-in-time	O
compilation	B-Language
to	O
generate	O
machine	O
code	O
as	O
it	O
is	O
loaded	O
.	O
</s>
<s>
is	O
an	O
experimental	O
Racket	O
to	O
JavaScript	O
(	O
ES6	O
)	O
compiler	B-Language
.	O
</s>
<s>
Apart	O
from	O
having	O
a	O
basis	O
in	O
programming	O
language	O
theory	O
,	O
Racket	O
was	O
designed	O
as	O
a	O
general-purpose	B-Language
language	O
for	O
production	O
systems	O
.	O
</s>
<s>
Thus	O
,	O
the	O
Racket	O
distribution	O
features	O
an	O
extensive	O
library	O
that	O
covers	O
systems	O
and	O
network	O
programming	O
,	O
web	O
development	O
,	O
a	O
uniform	O
interface	O
to	O
the	O
underlying	O
operating	B-General_Concept
system	I-General_Concept
,	O
a	O
dynamic	O
foreign	B-Application
function	I-Application
interface	I-Application
,	O
several	O
flavours	O
of	O
regular	B-Language
expressions	I-Language
,	O
lexer/parser	O
generators	O
,	O
logic	B-Language
programming	I-Language
,	O
and	O
a	O
complete	O
GUI	B-Library
framework	I-Library
.	O
</s>
<s>
Racket	O
has	O
several	O
features	O
useful	O
for	O
a	O
commercial	O
language	O
,	O
among	O
them	O
an	O
ability	O
to	O
compile	B-Language
standalone	O
executables	O
under	O
Windows	B-Application
,	O
macOS	B-Application
,	O
and	O
Unix	B-Application
,	O
a	O
profiler	O
and	O
debugger	B-Application
included	O
in	O
the	O
integrated	B-Application
development	I-Application
environment	I-Application
(	O
IDE	B-Application
)	O
,	O
and	O
a	O
unit	O
testing	O
framework	O
.	O
</s>
<s>
A	O
notable	O
example	O
is	O
the	O
Hacker	B-Application
News	I-Application
website	O
,	O
which	O
runs	O
on	O
Arc	B-Operating_System
,	O
which	O
is	O
developed	O
in	O
Racket	O
.	O
</s>
<s>
Naughty	O
Dog	O
has	O
used	O
it	O
as	O
a	O
scripting	B-Language
language	I-Language
in	O
several	O
of	O
their	O
video	O
games	O
.	O
</s>
