<s>
META	B-Application
II	I-Application
is	O
a	O
domain-specific	B-Language
programming	I-Language
language	I-Language
for	O
writing	O
compilers	B-Language
.	O
</s>
<s>
META	B-Application
II	I-Application
uses	O
what	O
Schorre	O
called	O
syntax	O
equations	O
.	O
</s>
<s>
Meta	B-Application
II	I-Application
programs	O
are	O
compiled	B-Language
into	O
an	O
interpreted	O
byte	O
code	O
language	O
.	O
</s>
<s>
VALGOL	O
and	O
SMALGOL	O
compilers	B-Language
illustrating	O
its	O
capabilities	O
were	O
written	O
in	O
the	O
META	B-Application
II	I-Application
language	O
,	O
VALGOL	O
is	O
a	O
simple	O
algebraic	O
language	O
designed	O
for	O
the	O
purpose	O
of	O
illustrating	O
META	B-Application
II	I-Application
.	O
</s>
<s>
SMALGOL	O
was	O
a	O
fairly	O
large	O
subset	O
of	O
ALGOL	B-Language
60	I-Language
.	O
</s>
<s>
META	B-Application
II	I-Application
was	O
first	O
written	O
in	O
META	O
I	O
,	O
a	O
hand-compiled	O
version	O
of	O
META	B-Application
II	I-Application
.	O
</s>
<s>
The	O
history	O
is	O
unclear	O
as	O
to	O
whether	O
META	O
I	O
was	O
a	O
full	O
implementation	O
of	O
META	B-Application
II	I-Application
or	O
a	O
required	O
subset	O
of	O
the	O
META	B-Application
II	I-Application
language	O
required	O
to	O
compile	B-Language
the	O
full	O
META	B-Application
II	I-Application
compiler	B-Language
.	O
</s>
<s>
In	O
its	O
documentation	O
,	O
META	B-Application
II	I-Application
is	O
described	O
as	O
resembling	O
BNF	O
,	O
which	O
today	O
is	O
explained	O
as	O
a	O
production	O
grammar	O
.	O
</s>
<s>
META	B-Application
II	I-Application
is	O
an	O
analytical	O
grammar	O
.	O
</s>
<s>
In	O
the	O
TREE-META	B-Application
document	O
these	O
languages	O
were	O
described	O
as	O
reductive	O
grammars	O
.	O
</s>
<s>
A	O
parser	B-Language
does	O
the	O
opposite	O
taking	O
language	O
constructs	O
apart	O
.	O
</s>
<s>
META	B-Application
II	I-Application
is	O
a	O
stack-based	B-Language
functional	B-Language
parser	B-Language
programming	O
language	O
that	O
includes	O
output	O
directive	O
.	O
</s>
<s>
In	O
META	B-Application
II	I-Application
,	O
the	O
order	O
of	O
testing	O
is	O
specified	O
by	O
the	O
equation	O
.	O
</s>
<s>
META	B-Application
II	I-Application
like	O
other	O
programming	O
languages	O
would	O
overflow	O
its	O
stack	O
attempting	O
left	O
recursion	O
.	O
</s>
<s>
META	B-Application
II	I-Application
uses	O
a	O
$	O
(	O
zero	O
or	O
more	O
)	O
sequence	O
operator	O
.	O
</s>
<s>
The	O
expr	O
parsing	O
equation	O
written	O
in	O
META	B-Application
II	I-Application
is	O
a	O
conditional	O
expression	O
evaluated	O
left	O
to	O
right	O
:	O
</s>
<s>
Schorre	O
describes	O
this	O
as	O
being	O
an	O
aid	O
to	O
efficiency	O
,	O
but	O
unlike	O
a	O
naive	O
recursive	B-Application
descent	I-Application
compiler	B-Language
it	O
will	O
also	O
ensure	O
that	O
the	O
associativity	O
of	O
arithmetic	O
operations	O
is	O
correct	O
:	O
</s>
<s>
META	B-Application
II	I-Application
outputs	O
assembly	O
code	O
for	O
a	O
stack	O
machine	O
.	O
</s>
<s>
META	B-Application
II	I-Application
is	O
the	O
first	O
documented	O
version	O
of	O
a	O
metacompiler	B-Language
,	O
as	O
it	O
compiles	B-Language
to	O
machine	O
code	O
for	O
one	O
of	O
the	O
earliest	O
instances	O
of	O
a	O
virtual	B-Architecture
machine	I-Architecture
.	O
</s>
<s>
The	O
paper	O
itself	O
is	O
a	O
wonderful	O
gem	O
which	O
includes	O
a	O
number	O
of	O
excellent	O
examples	O
,	O
including	O
the	O
bootstrapping	O
of	O
Meta	B-Application
II	I-Application
in	O
itself	O
(	O
all	O
this	O
was	O
done	O
on	O
an	O
8K	O
(	O
six	O
bit	O
byte	O
)	O
1401	O
!	O
)	O
.	O
</s>
<s>
The	O
paper	O
included	O
a	O
listing	O
of	O
the	O
description	O
of	O
Meta	B-Application
II	I-Application
,	O
this	O
could	O
in	O
principle	O
be	O
processed	O
manually	O
to	O
yield	O
an	O
interpretable	O
program	O
in	O
virtual	B-Architecture
machine	I-Architecture
opcodes	O
;	O
if	O
this	O
ran	O
and	O
produced	O
identical	O
output	O
then	O
the	O
implementation	O
was	O
correct	O
.	O
</s>
<s>
META	B-Application
II	I-Application
was	O
basically	O
a	O
proof	O
of	O
concept	O
.	O
</s>
<s>
META	B-Application
II	I-Application
is	O
not	O
presented	O
as	O
a	O
standard	O
language	O
,	O
but	O
as	O
a	O
point	O
of	O
departure	O
from	O
which	O
a	O
user	O
may	O
develop	O
his	O
own	O
META	O
"	O
language	O
"	O
.	O
</s>
<s>
Schorre	O
went	O
to	O
work	O
for	O
System	O
Development	O
Corporation	O
where	O
he	O
was	O
a	O
member	O
of	O
the	O
Compiler	B-Language
for	O
Writing	O
and	O
Implementing	O
Compilers	B-Language
(	O
CWIC	O
)	O
project	O
.	O
</s>
<s>
CWIC	O
's	O
SYNTAX	O
language	O
built	O
on	O
META	B-Application
II	I-Application
adding	O
a	O
backtrack	O
alternative	O
operator	O
positive	O
and	O
negative	O
look	O
ahead	O
operators	O
and	O
programmed	O
token	O
equations	O
.	O
</s>
<s>
The	O
GENERATOR	O
language	O
based	O
on	O
LISP	B-Language
2	I-Language
processed	O
the	O
trees	O
produced	O
by	O
the	O
SYNTAX	O
parsing	O
language	O
.	O
</s>
<s>
These	O
languages	O
were	O
developed	O
by	O
members	O
of	O
the	O
L.A.	O
ACM	O
SIGPLAN	O
sub-group	O
on	O
Syntax	O
Directed	O
Compilers	B-Language
.	O
</s>
<s>
It	O
is	O
notable	O
how	O
Schorre	O
thought	O
of	O
the	O
META	B-Application
II	I-Application
language	O
:	O
</s>
<s>
The	O
term	O
META	O
"	O
language	O
"	O
with	O
META	O
in	O
capital	O
letters	O
is	O
used	O
to	O
denote	O
any	O
compiler-writing	O
language	O
so	O
developed	O
.	O
</s>
<s>
Schorre	O
explains	O
META	B-Application
II	I-Application
as	O
a	O
base	O
from	O
which	O
other	O
META	O
"	O
languages	O
"	O
may	O
be	O
developed	O
.	O
</s>
