<s>
The	O
J	B-Language
programming	I-Language
language	I-Language
,	O
developed	O
in	O
the	O
early	O
1990s	O
by	O
Kenneth	O
E	O
.	O
Iverson	O
and	O
Roger	O
Hui	O
,	O
is	O
an	O
array	B-Application
programming	I-Application
language	I-Application
based	O
primarily	O
on	O
APL	B-Language
(	O
also	O
by	O
Iverson	O
)	O
.	O
</s>
<s>
To	O
avoid	O
repeating	O
the	O
APL	B-Language
special-character	O
problem	O
,	O
J	B-Language
uses	O
only	O
the	O
basic	O
ASCII	B-Protocol
character	I-Protocol
set	I-Protocol
,	O
resorting	O
to	O
the	O
use	O
of	O
the	O
dot	O
and	O
colon	O
as	O
inflections	O
to	O
form	O
short	O
words	O
similar	O
to	O
digraphs	B-Language
.	O
</s>
<s>
Most	O
such	O
primary	O
(	O
or	O
primitive	O
)	O
J	B-Language
words	O
serve	O
as	O
mathematical	O
symbols	O
,	O
with	O
the	O
dot	O
or	O
colon	O
extending	O
the	O
meaning	O
of	O
the	O
basic	O
characters	O
available	O
.	O
</s>
<s>
Also	O
,	O
many	O
characters	O
which	O
in	O
other	O
languages	O
often	O
must	O
be	O
paired	O
(	O
such	O
as	O
 [  ] 	O
 {  } 	O
""	O
``	O
or	O
<>	O
)	O
are	O
treated	O
by	O
J	B-Language
as	O
stand-alone	O
words	O
or	O
,	O
when	O
inflected	O
,	O
as	O
single-character	O
roots	O
of	O
multi-character	O
words	O
.	O
</s>
<s>
J	B-Language
is	O
a	O
very	O
terse	O
array	B-Application
programming	I-Application
language	I-Application
,	O
and	O
is	O
most	O
suited	O
to	O
mathematical	O
and	O
statistical	O
programming	O
,	O
especially	O
when	O
performing	O
operations	O
on	O
matrices	B-Architecture
.	O
</s>
<s>
Like	O
John	O
Backus	O
's	O
languages	O
FP	B-Language
and	O
FL	B-Language
,	O
J	B-Language
supports	O
function-level	B-Application
programming	I-Application
via	O
its	O
tacit	B-Application
programming	I-Application
features	O
.	O
</s>
<s>
Unlike	O
most	O
languages	O
that	O
support	O
object-oriented	B-Language
programming	I-Language
,	O
J	B-Language
's	O
flexible	O
hierarchical	O
namespace	O
scheme	O
(	O
where	O
every	O
name	O
exists	O
in	O
a	O
specific	O
locale	O
)	O
can	O
be	O
effectively	O
used	O
as	O
a	O
framework	O
for	O
both	O
class-based	B-Application
and	O
prototype-based	B-Application
object-oriented	B-Language
programming	I-Language
.	O
</s>
<s>
Since	O
March	O
2011	O
,	O
J	B-Language
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
version	O
3	O
(	O
GPLv3	B-License
)	O
.	O
</s>
<s>
J	B-Language
permits	O
point-free	B-Application
style	I-Application
and	O
function	B-Application
composition	I-Application
.	O
</s>
<s>
program	O
in	O
J	B-Language
is	O
:	O
</s>
<s>
This	O
implementation	O
of	O
hello	O
world	O
reflects	O
the	O
traditional	O
use	O
of	O
J	B-Language
–	O
programs	O
are	O
entered	O
into	O
a	O
J	B-Language
interpreter	O
session	O
,	O
and	O
the	O
results	O
of	O
expressions	O
are	O
displayed	O
.	O
</s>
<s>
It	O
's	O
also	O
possible	O
to	O
arrange	O
for	O
J	B-Language
scripts	O
to	O
be	O
executed	O
as	O
standalone	O
programs	O
.	O
</s>
<s>
Here	O
's	O
how	O
this	O
might	O
look	O
on	O
a	O
Unix	B-Application
system	I-Application
:	O
</s>
<s>
(	O
Note	O
that	O
current	O
j	B-Language
implementations	O
install	O
either	O
jconsole	O
or	O
(	O
because	O
jconsole	O
is	O
used	O
by	O
java	O
)	O
,	O
ijconsole	O
and	O
likely	O
install	O
this	O
to	O
/usr/bin	O
or	O
some	O
other	O
directory	O
(	O
perhaps	O
the	O
Application	O
directory	O
on	O
OSX	O
)	O
.	O
</s>
<s>
Historically	O
,	O
APL	B-Language
used	O
/	O
to	O
indicate	O
the	O
fold	B-Application
,	O
so	O
+	O
/1	O
2	O
3	O
was	O
equivalent	O
to	O
1+2+3	O
.	O
</s>
<s>
Because	O
ASCII	B-Protocol
does	O
not	O
include	O
a	O
division	O
symbol	O
per	O
se	O
,	O
J	B-Language
uses	O
%	O
to	O
represent	O
division	O
,	O
as	O
a	O
visual	O
approximation	O
or	O
reminder	O
.	O
</s>
<s>
(	O
This	O
illustrates	O
something	O
of	O
the	O
mnemonic	O
character	O
of	O
J	B-Language
's	O
tokens	O
,	O
and	O
some	O
of	O
the	O
quandaries	O
imposed	O
by	O
the	O
use	O
of	O
ASCII	B-Protocol
.	O
)	O
</s>
<s>
Defining	O
a	O
J	B-Language
function	O
named	O
avg	O
to	O
calculate	O
the	O
average	O
of	O
a	O
list	O
of	O
numbers	O
yields	O
:	O
</s>
<s>
+	O
/	O
sums	O
the	O
items	O
of	O
the	O
array	B-Application
.	O
</s>
<s>
#	O
counts	O
the	O
number	O
of	O
items	O
in	O
the	O
array	B-Application
.	O
</s>
<s>
Specifically	O
,	O
(	O
V0	O
V1	O
V2	O
)	O
Ny	O
is	O
the	O
same	O
as	O
(V0(Ny )	O
)	O
V1	O
(V2(Ny )	O
)	O
which	O
shows	O
some	O
of	O
the	O
power	O
of	O
J	B-Language
.	O
</s>
<s>
Rank	B-Language
is	O
a	O
crucial	O
concept	O
in	O
J	B-Language
.	O
</s>
<s>
Its	O
significance	O
in	O
J	B-Language
is	O
similar	O
to	O
the	O
significance	O
of	O
select	O
in	O
SQL	B-Language
and	O
of	O
while	O
in	O
C	B-Language
.	O
</s>
<s>
Implementing	O
quicksort	B-Algorithm
,	O
from	O
the	O
J	B-Language
Dictionary	O
yields	O
:	O
</s>
<s>
The	O
following	O
is	O
an	O
implementation	O
of	O
quicksort	B-Algorithm
demonstrating	O
tacit	B-Application
programming	I-Application
.	O
</s>
<s>
J	B-Language
's	O
support	O
for	O
forks	O
and	O
hooks	O
dictates	O
rules	O
on	O
how	O
arguments	O
applied	O
to	O
this	O
function	O
will	O
be	O
applied	O
to	O
its	O
component	O
functions	O
.	O
</s>
<s>
Sorting	O
in	O
J	B-Language
is	O
usually	O
accomplished	O
using	O
the	O
built-in	O
(	O
primitive	O
)	O
verbs	O
/	O
:	O
(	O
sort	O
up	O
)	O
and	O
\	O
:	O
(	O
sort	O
down	O
)	O
.	O
</s>
<s>
User-defined	O
sorts	O
such	O
as	O
quicksort	B-Algorithm
,	O
above	O
,	O
typically	O
are	O
for	O
illustration	O
only	O
.	O
</s>
<s>
The	O
following	O
expression	O
exhibits	O
pi	O
with	O
n	O
digits	O
and	O
demonstrates	O
the	O
extended	O
precision	O
abilities	O
of	O
J	B-Language
:	O
</s>
<s>
J	B-Language
has	O
a	O
rich	O
set	O
of	O
predefined	O
verbs	O
,	O
all	O
of	O
which	O
work	O
on	O
multiple	O
data	O
types	O
automatically	O
:	O
for	O
example	O
,	O
the	O
verb	O
searches	O
within	O
arrays	O
of	O
any	O
size	O
to	O
find	O
matches	O
:	O
</s>
<s>
The	O
power	O
of	O
J	B-Language
comes	O
largely	O
from	O
its	O
modifiers	O
:	O
symbols	O
that	O
take	O
nouns	O
and	O
verbs	O
as	O
operands	O
and	O
apply	O
the	O
operands	O
in	O
a	O
specified	O
way	O
.	O
</s>
<s>
J	B-Language
has	O
roughly	O
two	O
dozen	O
of	O
these	O
modifiers	O
.	O
</s>
<s>
J	B-Language
supports	O
three	O
simple	O
types	O
:	O
</s>
<s>
One	O
of	O
J	B-Language
's	O
numeric	O
types	O
is	O
the	O
bit	O
.	O
</s>
<s>
Syntactically	O
,	O
the	O
J	B-Language
parser	O
treats	O
that	O
as	O
one	O
word	O
.	O
</s>
<s>
Further	O
,	O
J	B-Language
supports	O
all	O
the	O
usual	O
binary	O
operations	O
on	O
these	O
lists	O
,	O
such	O
as	O
and	O
,	O
or	O
,	O
exclusive	O
or	O
,	O
rotate	O
,	O
shift	O
,	O
not	O
,	O
etc	O
.	O
</s>
<s>
J	B-Language
also	O
supports	O
higher	O
order	O
arrays	O
of	O
bits	O
.	O
</s>
<s>
As	O
with	O
bits	O
,	O
operations	O
are	O
performed	O
on	O
all	O
numbers	O
in	O
an	O
array	B-Application
.	O
</s>
<s>
(	O
When	O
parsing	O
J	B-Language
,	O
.	O
</s>
<s>
J	B-Language
also	O
supports	O
the	O
literal	O
(	O
character	O
)	O
type	O
.	O
</s>
<s>
Typically	O
,	O
individual	O
literals	O
are	O
8-bits	O
wide	O
(	O
ASCII	B-Protocol
)	O
,	O
but	O
J	B-Language
also	O
supports	O
other	O
literals	O
(	O
Unicode	O
)	O
.	O
</s>
<s>
This	O
is	O
analogous	O
to	O
C	B-Language
's	O
&	O
operation	O
(	O
with	O
no	O
left	O
argument	O
)	O
.	O
</s>
<s>
However	O
,	O
where	O
the	O
result	O
of	O
C	B-Language
's	O
&	O
has	O
reference	O
semantics	O
,	O
the	O
result	O
of	O
J	B-Language
's	O
<	O
has	O
value	O
semantics	O
.	O
</s>
<s>
From	O
the	O
viewpoint	O
of	O
a	O
J	B-Language
programmer	O
,	O
<	O
puts	O
the	O
data	O
into	O
a	O
box	O
and	O
allows	O
working	O
with	O
an	O
array	B-Application
of	O
boxes	O
(	O
it	O
can	O
be	O
assembled	O
with	O
other	O
boxes	O
,	O
and/or	O
more	O
copies	O
can	O
be	O
made	O
of	O
the	O
box	O
)	O
.	O
</s>
<s>
The	O
only	O
collection	O
type	O
offered	O
by	O
J	B-Language
is	O
the	O
arbitrarily	O
dimensioned	O
array	B-Application
.	O
</s>
<s>
J	B-Language
's	O
arrays	O
are	O
homogeneously	O
typed	O
,	O
for	O
example	O
the	O
list	O
1	O
2	O
3	O
is	O
a	O
list	O
of	O
integers	O
despite	O
1	O
being	O
a	O
bit	O
.	O
</s>
<s>
J	B-Language
also	O
supports	O
sparse	O
numeric	O
arrays	O
where	O
non-zero	O
values	O
are	O
stored	O
with	O
their	O
indices	O
.	O
</s>
<s>
J	B-Language
also	O
supports	O
objects	O
and	O
classes	O
,	O
but	O
these	O
are	O
an	O
artifact	O
of	O
the	O
way	O
things	O
are	O
named	O
,	O
and	O
are	O
not	O
data	O
types	O
.	O
</s>
<s>
J	B-Language
data	O
has	O
value	O
semantics	O
,	O
but	O
objects	O
and	O
classes	O
need	O
reference	O
semantics	O
.	O
</s>
<s>
J	B-Language
has	O
the	O
usual	O
facilities	O
for	O
stopping	O
on	O
error	O
or	O
at	O
specified	O
places	O
within	O
verbs	O
.	O
</s>
<s>
It	O
also	O
has	O
a	O
unique	O
visual	O
debugger	O
,	O
called	O
,	O
that	O
gives	O
a	O
2-D	O
interactive	O
display	O
of	O
the	O
execution	O
of	O
a	O
single	O
J	B-Language
sentence	O
.	O
</s>
<s>
Because	O
a	O
single	O
sentence	O
of	O
J	B-Language
performs	O
as	O
much	O
computation	O
as	O
an	O
entire	O
subroutine	O
in	O
lower-level	O
languages	O
,	O
the	O
visual	O
display	O
is	O
quite	O
helpful	O
.	O
</s>
<s>
J	B-Language
's	O
documentation	O
includes	O
a	O
,	O
with	O
words	O
in	O
J	B-Language
identified	O
as	O
,	O
,	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
J	B-Language
provides	O
control	O
structures	O
similar	O
to	O
other	O
procedural	O
languages	O
.	O
</s>
