<s>
Lisp	B-Language
Flavored	O
Erlang	B-Operating_System
(	O
LFE	B-Language
)	O
is	O
a	O
functional	B-Language
,	O
concurrent	B-Architecture
,	O
garbage	B-General_Concept
collected	I-General_Concept
,	O
general-purpose	O
programming	O
language	O
and	O
Lisp	B-Language
dialect	O
built	O
on	O
Core	B-Operating_System
Erlang	I-Operating_System
and	O
the	O
Erlang	B-Application
virtual	I-Application
machine	I-Application
(	O
BEAM	B-Application
)	O
.	O
</s>
<s>
LFE	B-Language
builds	O
on	O
Erlang	B-Operating_System
to	O
provide	O
a	O
Lisp	B-Language
syntax	O
for	O
writing	O
distributed	O
,	O
fault-tolerant	B-General_Concept
,	O
soft	O
real-time	B-General_Concept
,	O
non-stop	O
applications	O
.	O
</s>
<s>
LFE	B-Language
also	O
extends	O
Erlang	B-Operating_System
to	O
support	O
metaprogramming	B-Application
with	O
Lisp	B-Language
macros	O
and	O
an	O
improved	O
developer	O
experience	O
with	O
a	O
feature-rich	O
read	B-Application
–	I-Application
eval	I-Application
–	I-Application
print	I-Application
loop	I-Application
(	O
REPL	B-Application
)	O
.	O
</s>
<s>
LFE	B-Language
is	O
actively	O
supported	O
on	O
all	O
recent	O
releases	O
of	O
Erlang	B-Operating_System
;	O
the	O
oldest	O
version	O
of	O
Erlang	B-Operating_System
supported	O
is	O
R14	O
.	O
</s>
<s>
Initial	O
work	O
on	O
LFE	B-Language
began	O
in	O
2007	O
,	O
when	O
Robert	O
Virding	O
started	O
creating	O
a	O
prototype	O
of	O
Lisp	B-Language
running	O
on	O
Erlang	B-Operating_System
.	O
</s>
<s>
Virding	O
announced	O
the	O
first	O
release	O
of	O
LFE	B-Language
on	O
the	O
Erlang	B-Operating_System
Questions	O
mail	O
list	O
in	O
March	O
2008	O
.	O
</s>
<s>
This	O
release	O
of	O
LFE	B-Language
was	O
very	O
limited	O
:	O
it	O
did	O
not	O
handle	O
recursive	O
letrecs	O
,	O
binarys	O
,	O
receive	O
,	O
or	O
try	O
;	O
it	O
also	O
did	O
not	O
support	O
a	O
Lisp	B-Language
shell	O
.	O
</s>
<s>
Initial	O
development	O
of	O
LFE	B-Language
was	O
done	O
with	O
version	O
R12B-0	O
of	O
Erlang	B-Operating_System
on	O
a	O
Dell	O
XPS	O
laptop	O
.	O
</s>
<s>
Robert	O
Virding	O
has	O
stated	O
that	O
there	O
were	O
several	O
reasons	O
why	O
he	O
started	O
the	O
LFE	B-Language
programming	O
language	O
:	O
</s>
<s>
He	O
had	O
prior	O
experience	O
programming	O
in	O
Lisp	B-Language
.	O
</s>
<s>
Given	O
his	O
prior	O
experience	O
,	O
he	O
was	O
interested	O
in	O
implementing	O
his	O
own	O
Lisp	B-Language
.	O
</s>
<s>
In	O
particular	O
,	O
he	O
wanted	O
to	O
implement	O
a	O
Lisp	B-Language
in	O
Erlang	B-Operating_System
:	O
not	O
only	O
was	O
he	O
curious	O
to	O
see	O
how	O
it	O
would	O
run	O
on	O
and	O
integrate	O
with	O
Erlang	B-Operating_System
,	O
he	O
wanted	O
to	O
see	O
what	O
it	O
would	O
look	O
like	O
.	O
</s>
<s>
Since	O
helping	O
to	O
create	O
the	O
Erlang	B-Operating_System
programming	I-Operating_System
language	I-Operating_System
,	O
he	O
had	O
had	O
the	O
goal	O
of	O
making	O
a	O
Lisp	B-Language
which	O
was	O
specifically	O
designed	O
to	O
run	O
on	O
the	O
BEAM	B-Application
and	O
able	O
to	O
fully	O
interact	O
with	O
Erlang/OTP	B-Operating_System
.	O
</s>
<s>
He	O
wanted	O
to	O
experiment	O
with	O
compiling	B-Language
another	O
language	O
on	O
Erlang	B-Operating_System
.	O
</s>
<s>
As	O
such	O
,	O
he	O
saw	O
LFE	B-Language
as	O
a	O
means	O
to	O
explore	O
this	O
by	O
generating	O
Core	B-Operating_System
Erlang	I-Operating_System
and	O
plugging	O
it	O
into	O
the	O
backend	O
of	O
the	O
Erlang	B-Operating_System
compiler	B-Language
.	O
</s>
<s>
Like	O
Lisp	B-Language
,	O
LFE	B-Language
is	O
an	O
expression-oriented	O
language	O
.	O
</s>
<s>
Unlike	O
non-homoiconic	O
programming	O
languages	O
,	O
Lisps	B-Language
make	O
no	O
or	O
little	O
syntactic	O
distinction	O
between	O
expressions	O
and	O
statements	O
:	O
all	O
code	O
and	O
data	O
are	O
written	O
as	O
expressions	O
.	O
</s>
<s>
LFE	B-Language
brought	O
homoiconicity	O
to	O
the	O
Erlang	B-Operating_System
VM	O
.	O
</s>
<s>
In	O
LFE	B-Language
,	O
the	O
list	O
data	O
type	O
is	O
written	O
with	O
its	O
elements	O
separated	O
by	O
whitespace	O
,	O
and	O
surrounded	O
by	O
parentheses	O
.	O
</s>
<s>
These	O
values	O
are	O
implicitly	O
typed	O
:	O
they	O
are	O
respectively	O
two	O
integers	O
and	O
a	O
Lisp-specific	O
data	O
type	O
called	O
a	O
symbolic	O
atom	O
,	O
and	O
need	O
not	O
be	O
declared	O
as	O
such	O
.	O
</s>
<s>
As	O
seen	O
in	O
the	O
example	O
above	O
,	O
LFE	B-Language
expressions	O
are	O
written	O
as	O
lists	O
,	O
using	O
prefix	O
notation	O
.	O
</s>
<s>
The	O
LFE-Erlang	O
operators	O
are	O
used	O
in	O
the	O
same	O
way	O
.	O
</s>
<s>
Unlike	O
functions	O
in	O
Erlang	B-Operating_System
and	O
LFE	B-Language
,	O
arithmetic	O
operators	O
in	O
Lisp	B-Language
are	O
variadic	B-Language
(	O
or	O
n-ary	O
)	O
,	O
able	O
to	O
take	O
any	O
number	O
of	O
arguments	O
.	O
</s>
<s>
LFE	B-Language
has	O
lambda	O
,	O
just	O
like	O
Common	B-Language
Lisp	I-Language
.	O
</s>
<s>
It	O
also	O
,	O
however	O
,	O
has	O
lambda-match	O
to	O
account	O
for	O
Erlang	B-Operating_System
's	O
pattern-matching	B-Language
abilities	O
in	O
anonymous	O
function	O
calls	O
.	O
</s>
<s>
This	O
section	O
does	O
not	O
represent	O
a	O
complete	O
comparison	O
between	O
Erlang	B-Operating_System
and	O
LFE	B-Language
,	O
but	O
should	O
give	O
a	O
taste	O
.	O
</s>
<s>
Erlang	B-Operating_System
:	O
</s>
<s>
LFE	B-Language
:	O
</s>
<s>
Erlang	B-Operating_System
:	O
</s>
<s>
LFE	B-Language
:	O
</s>
<s>
Or	O
idiomatic	O
functional	B-Language
style	O
:	O
</s>
<s>
Erlang	B-Operating_System
:	O
</s>
<s>
LFE	B-Language
:	O
</s>
<s>
Erlang	B-Operating_System
:	O
</s>
<s>
LFE	B-Language
:	O
</s>
<s>
Erlang	B-Operating_System
:	O
</s>
<s>
LFE	B-Language
:	O
</s>
<s>
Erlang	B-Operating_System
:	O
</s>
<s>
LFE	B-Language
:	O
</s>
<s>
Calls	O
to	O
Erlang	B-Operating_System
functions	O
take	O
the	O
form	O
(	O
<module>:<function> <arg1> ... <argn>	O
)	O
:	O
</s>
<s>
Message-passing	O
with	O
Erlang	B-Operating_System
's	O
light-weight	O
"	O
processes	O
"	O
:	O
</s>
