<s>
T	B-Language
is	O
a	O
dialect	O
of	O
the	O
Scheme	B-Language
programming	I-Language
language	I-Language
developed	O
in	O
the	O
early	O
1980s	O
by	O
Jonathan	O
A	O
.	O
Rees	O
,	O
Kent	O
M	O
.	O
Pitman	O
,	O
and	O
Norman	O
I	O
.	O
Adams	O
of	O
Yale	O
University	O
as	O
an	O
experiment	O
in	O
language	O
design	O
and	O
implementation	O
.	O
</s>
<s>
T	B-Language
's	O
purpose	O
is	O
to	O
test	O
the	O
thesis	O
developed	O
by	O
Guy	O
L	O
.	O
Steele	O
Jr.	O
and	O
Gerald	O
Jay	O
Sussman	O
in	O
their	O
series	O
of	O
papers	O
about	O
Scheme	B-Language
:	O
that	O
Scheme	B-Language
may	O
be	O
used	O
as	O
the	O
basis	O
for	O
a	O
practical	O
programming	O
language	O
of	O
exceptional	O
expressive	O
power	O
,	O
and	O
that	O
implementations	O
of	O
Scheme	B-Language
could	O
perform	O
better	O
than	O
other	O
Lisp	B-Language
systems	O
,	O
and	O
competitively	O
with	O
implementations	O
of	O
programming	O
languages	O
,	O
such	O
as	O
C	B-Language
and	O
BLISS	B-Language
,	O
which	O
are	O
usually	O
considered	O
to	O
be	O
inherently	O
more	O
efficient	O
than	O
Lisp	B-Language
on	O
conventional	O
machine	O
architectures	O
.	O
</s>
<s>
Much	O
of	O
this	O
occurs	O
via	O
an	O
optimizing	B-Application
compiler	I-Application
named	O
Orbit	O
.	O
</s>
<s>
T	B-Language
contains	O
some	O
features	O
that	O
modern	O
Scheme	B-Language
lacks	O
.	O
</s>
<s>
For	O
example	O
,	O
T	B-Language
is	O
object-oriented	B-Language
,	O
and	O
it	O
has	O
first-class	O
environments	O
,	O
called	O
locales	O
,	O
which	O
can	O
be	O
modified	O
non-locally	O
and	O
used	O
as	O
a	O
module	O
system	O
.	O
</s>
<s>
T	B-Language
has	O
several	O
extra	O
special	O
forms	O
for	O
lazy	O
evaluation	O
and	O
flow	O
control	O
,	O
and	O
an	O
equivalent	O
to	O
Common	B-Language
Lisp	I-Language
's	O
setf	O
.	O
</s>
<s>
T	B-Language
,	O
like	O
Scheme	B-Language
,	O
supports	O
call-with-current-continuation	O
(	O
call/cc	O
)	O
,	O
but	O
it	O
also	O
has	O
a	O
more	O
limited	O
form	O
called	O
catch	O
.	O
</s>
<s>
From	O
the	O
T	B-Language
manual	O
,	O
a	O
hypothetical	O
implementation	O
of	O
cons	B-Protocol
could	O
be	O
:	O
</s>
<s>
This	O
example	O
shows	O
that	O
objects	O
in	O
T	B-Language
are	O
intimately	O
related	O
to	O
closures	O
and	O
message-passing	O
.	O
</s>
<s>
A	O
primitive	O
called	O
join	O
puts	O
two	O
objects	O
together	O
,	O
allowing	O
for	O
something	O
resembling	O
inheritance	B-Language
.	O
</s>
<s>
T	B-Language
was	O
ported	O
to	O
many	O
hardware	B-Device
platforms	I-Device
and	O
operating	B-General_Concept
systems	I-General_Concept
,	O
including	O
:	O
</s>
