<s>
Impromptu	B-Language
is	O
a	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
programming	B-Application
environment	O
for	O
live	O
coding	O
.	O
</s>
<s>
Impromptu	B-Language
is	O
built	O
around	O
the	O
Scheme	B-Language
language	I-Language
,	O
which	O
is	O
a	O
member	O
of	O
the	O
Lisp	B-Language
family	O
of	O
languages	O
.	O
</s>
<s>
The	O
source	O
code	O
of	O
its	O
core	O
has	O
been	O
opened	O
as	O
the	O
Extempore	B-Application
project	I-Application
.	O
</s>
<s>
The	O
environment	O
allows	O
to	O
make	O
changes	O
to	O
a	O
program	O
at	B-Library
runtime	I-Library
,	O
so	O
variables	O
and	O
functions	O
may	O
be	O
redefined	O
and	O
the	O
changes	O
take	O
effect	O
immediately	O
.	O
</s>
<s>
The	O
library	O
allows	O
communicating	O
with	O
Audio	B-Operating_System
Units	I-Operating_System
for	O
audio	O
synthesis	O
,	O
and	O
with	O
graphics	O
layers	O
such	O
as	O
QuickTime	B-Application
,	O
Quartz	B-Operating_System
,	O
Core	B-Operating_System
Image	I-Operating_System
,	O
OpenGL	B-Application
for	O
video	O
composition	O
.	O
</s>
<s>
Code	O
written	O
in	O
Objective-C	B-Language
can	O
be	O
called	O
from	O
the	O
editor	O
,	O
and	O
also	O
Objective-C	B-Language
frameworks	O
can	O
perform	O
calls	O
to	O
the	O
Scheme	B-Language
interpreter	O
.	O
</s>
<s>
Impromptu	B-Language
's	O
Scheme	B-Language
interpreter	O
was	O
initially	O
built	O
from	O
the	O
TinyScheme	B-Language
1.35	O
baseline	O
,	O
but	O
it	O
has	O
been	O
substantially	O
modified	O
since	O
to	O
better	O
suit	O
the	O
live	O
coding	O
context	O
.	O
</s>
<s>
A	O
real-time	O
garbage	B-General_Concept
collector	I-General_Concept
,	O
and	O
Objective-C	B-Language
integration	O
were	O
added	O
.	O
</s>
<s>
Also	O
,	O
a	O
new	O
statically	O
typed	O
language	O
called	O
the	O
Extempore	B-Application
Language	O
has	O
been	O
integrated	O
to	O
the	O
system	O
.	O
</s>
<s>
This	O
language	O
is	O
syntactically	O
Scheme-like	O
,	O
but	O
semantically	O
closer	O
to	O
C	O
,	O
and	O
is	O
designed	O
for	O
real-time	O
sound	O
synthesis	O
and	O
other	O
computationally	O
heavy	O
tasks	O
.	O
</s>
<s>
It	O
provides	O
type	O
inference	O
and	O
is	O
compiled	O
to	O
machine	B-Language
language	I-Language
by	O
LLVM	B-Application
.	O
</s>
<s>
A	O
Study	O
in	O
Keith	O
is	O
a	O
live	O
coding	O
performance	O
in	O
Impromptu	B-Language
by	O
Andrew	O
Sorensen	O
.	O
</s>
<s>
The	O
core	O
of	O
Impromptu	B-Language
has	O
been	O
released	O
as	O
Extempore	B-Application
under	O
a	O
BSD	O
style	O
licence	O
.	O
</s>
<s>
It	O
runs	O
under	O
both	O
Linux	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
.	O
</s>
<s>
It	O
includes	O
the	O
Scheme	B-Language
interpreter	O
,	O
the	O
Extempore	B-Application
Language	O
compiler	O
and	O
the	O
scheduler	O
.	O
</s>
