<s>
POP-11	B-Language
is	O
a	O
reflective	B-Language
,	O
incrementally	B-Application
compiled	I-Application
programming	B-General_Concept
language	O
with	O
many	O
of	O
the	O
features	O
of	O
an	O
interpreted	B-Application
language	I-Application
.	O
</s>
<s>
It	O
is	O
the	O
core	O
language	O
of	O
the	O
Poplog	B-Language
programming	I-Language
environment	I-Language
developed	O
originally	O
by	O
the	O
University	O
of	O
Sussex	O
,	O
and	O
recently	O
in	O
the	O
School	O
of	O
Computer	O
Science	O
at	O
the	O
University	O
of	O
Birmingham	O
,	O
which	O
hosts	O
the	O
main	O
Poplog	B-Language
website	O
.	O
</s>
<s>
POP-11	B-Language
is	O
an	O
evolution	O
of	O
the	O
language	O
POP-2	B-Language
,	O
developed	O
in	O
Edinburgh	O
University	O
,	O
and	O
features	O
an	O
open	O
stack	B-Application
model	O
(	O
like	O
Forth	B-Application
,	O
among	O
others	B-Language
)	O
.	O
</s>
<s>
It	O
is	O
mainly	O
procedural	B-Application
,	O
but	O
supports	O
declarative	O
language	O
constructs	O
,	O
including	O
a	O
pattern	O
matcher	O
,	O
and	O
is	O
mostly	O
used	O
for	O
research	O
and	O
teaching	O
in	O
artificial	B-Application
intelligence	I-Application
,	O
although	O
it	O
has	O
features	O
sufficient	O
for	O
many	O
other	O
classes	O
of	O
problems	O
.	O
</s>
<s>
It	O
is	O
often	O
used	O
to	O
introduce	O
symbolic	O
programming	B-General_Concept
techniques	O
to	O
programmers	O
of	O
more	O
conventional	O
languages	O
like	O
Pascal	B-Application
,	O
who	O
find	O
POP	O
syntax	O
more	O
familiar	O
than	O
that	O
of	O
Lisp	B-Language
.	O
</s>
<s>
One	O
of	O
POP-11	B-Language
'	O
s	O
features	O
is	O
that	O
it	O
supports	O
first-class	B-Application
functions	I-Application
.	O
</s>
<s>
POP-11	B-Language
is	O
the	O
core	O
language	O
of	O
the	O
Poplog	B-Language
system	O
.	O
</s>
<s>
This	O
made	O
it	O
possible	O
for	O
(	O
optional	O
)	O
incremental	O
compilers	O
to	O
be	O
added	O
for	O
Prolog	B-Language
,	O
Common	B-Language
Lisp	I-Language
and	O
Standard	B-Language
ML	I-Language
,	O
which	O
could	O
be	O
added	O
as	O
required	O
to	O
support	O
either	O
mixed	O
language	O
development	O
or	O
development	O
in	O
the	O
second	O
language	O
without	O
using	O
any	O
POP-11	B-Language
constructs	O
.	O
</s>
<s>
This	O
made	O
it	O
possible	O
for	O
Poplog	B-Language
to	O
be	O
used	O
by	O
teachers	O
,	O
researchers	O
,	O
and	O
developers	O
who	O
were	O
interested	O
in	O
only	O
one	O
of	O
the	O
languages	O
.	O
</s>
<s>
The	O
most	O
successful	O
product	O
developed	O
in	O
POP-11	B-Language
was	O
the	O
Clementine	O
Data-mining	B-Application
system	O
,	O
developed	O
by	O
ISL	O
.	O
</s>
<s>
After	O
SPSS	O
bought	O
ISL	O
they	O
decided	O
to	O
port	O
Clementine	O
to	O
C++	O
and	O
Java	O
,	O
and	O
eventually	O
succeeded	O
with	O
great	O
effort	O
(	O
and	O
perhaps	O
some	O
loss	O
of	O
the	O
flexibility	O
provided	O
by	O
the	O
use	O
of	O
an	O
AI	B-Application
language	O
)	O
.	O
</s>
<s>
POP-11	B-Language
was	O
for	O
a	O
time	O
available	O
only	O
as	O
part	O
of	O
an	O
expensive	O
commercial	O
package	O
(	O
Poplog	B-Language
)	O
,	O
but	O
since	O
about	O
1999	O
it	O
has	O
been	O
freely	O
available	O
as	O
part	O
of	O
the	O
Open	O
Source	O
version	O
of	O
Poplog	B-Language
,	O
including	O
various	O
additional	O
packages	O
and	O
teaching	O
libraries	O
.	O
</s>
<s>
An	O
online	O
version	O
of	O
ELIZA	B-Application
using	O
POP-11	B-Language
is	O
available	O
at	O
Birmingham	O
.	O
</s>
<s>
At	O
the	O
University	O
of	O
Sussex	O
,	O
David	O
Young	O
used	O
POP-11	B-Language
in	O
combination	O
with	O
C	O
and	O
Fortran	O
to	O
develop	O
a	O
suite	O
of	O
teaching	O
and	O
interactive	O
development	O
tools	O
for	O
image	O
processing	O
and	O
vision	O
,	O
and	O
has	O
made	O
them	O
available	O
in	O
the	O
Popvision	O
extension	O
to	O
Poplog	B-Language
.	O
</s>
<s>
Here	O
is	O
an	O
example	O
of	O
a	O
simple	O
POP-11	B-Language
program	O
:	O
</s>
<s>
This	O
one	O
includes	O
some	O
list	B-Language
processing	I-Language
:	O
</s>
<s>
Examples	O
using	O
the	O
POP-11	B-Language
pattern	O
matcher	O
,	O
which	O
makes	O
it	O
relatively	O
easy	O
for	O
students	O
to	O
learn	O
to	O
develop	O
sophisticated	O
list-processing	O
programs	O
without	O
having	O
to	O
treat	O
patterns	O
as	O
tree	O
structures	O
accessed	O
by	O
'	O
head	O
 '	O
and	O
'	O
tail	O
 '	O
functions	O
(	O
CAR	O
and	O
CDR	O
in	O
Lisp	B-Language
)	O
,	O
can	O
be	O
found	O
in	O
the	O
.	O
</s>
