<s>
An	O
incremental	B-Application
compiler	I-Application
is	O
a	O
kind	O
of	O
incremental	O
computation	O
applied	O
to	O
the	O
field	O
of	O
compilation	B-Language
.	O
</s>
<s>
Quite	O
naturally	O
,	O
whereas	O
ordinary	O
compilers	B-Language
make	O
a	O
so-called	O
clean	O
build	O
,	O
that	O
is	O
,	O
(	O
re	O
)	O
build	O
all	O
program	O
modules	O
,	O
an	O
incremental	B-Application
compiler	I-Application
recompiles	B-Language
only	O
modified	O
portions	O
of	O
a	O
program	O
.	O
</s>
<s>
In	O
imperative	B-Application
programming	I-Application
and	O
software	O
development	O
,	O
incremental	B-Application
compilation	I-Application
takes	O
only	O
the	O
changes	O
of	O
a	O
known	O
set	O
of	O
source	O
files	O
and	O
updates	O
any	O
corresponding	O
output	O
files	O
(	O
in	O
the	O
compiler	B-Language
's	O
target	O
language	O
,	O
often	O
bytecode	O
)	O
that	O
may	O
already	O
exist	O
from	O
previous	O
compilations	B-Language
.	O
</s>
<s>
By	O
effectively	O
building	O
upon	O
previously	O
compiled	B-Language
output	O
files	O
,	O
an	O
incremental	B-Application
compiler	I-Application
avoids	O
the	O
wasteful	O
recompiling	O
of	O
entire	O
source	O
files	O
,	O
where	O
most	O
of	O
the	O
code	O
remains	O
unchanged	O
.	O
</s>
<s>
For	O
most	O
incremental	B-Application
compilers	I-Application
,	O
compiling	B-Language
a	O
program	O
with	O
small	O
changes	O
to	O
its	O
source	O
code	O
is	O
usually	O
near	O
instantaneous	O
.	O
</s>
<s>
It	O
can	O
be	O
said	O
that	O
an	O
incremental	B-Application
compiler	I-Application
reduces	O
the	O
granularity	O
of	O
a	O
language	O
's	O
traditional	O
compiling	B-Language
units	O
while	O
maintaining	O
the	O
language	O
's	O
semantics	B-Application
,	O
such	O
that	O
the	O
compiler	B-Language
can	O
append	O
and	O
replace	O
smaller	O
parts	O
.	O
</s>
<s>
Many	O
programming	B-Application
tools	I-Application
take	O
advantage	O
of	O
incremental	B-Application
compilers	I-Application
to	O
provide	O
developers	O
with	O
a	O
much	O
more	O
interactive	B-Application
programming	I-Application
environment	O
.	O
</s>
<s>
It	O
is	O
not	O
unusual	O
that	O
an	O
incremental	B-Application
compiler	I-Application
is	O
invoked	O
for	O
every	O
change	O
of	O
a	O
source	O
file	O
,	O
such	O
that	O
the	O
developer	O
is	O
almost	O
immediately	O
informed	O
about	O
any	O
compilation	B-Error_Name
errors	I-Error_Name
that	O
would	O
arise	O
as	O
a	O
result	O
of	O
his	O
changes	O
to	O
the	O
code	O
.	O
</s>
<s>
This	O
scheme	B-Language
,	O
in	O
contrast	O
with	O
traditional	O
compilation	B-Language
,	O
shortens	O
a	O
programmer	O
's	O
development	O
cycle	O
significantly	O
,	O
because	O
they	O
would	O
no	O
longer	O
have	O
to	O
wait	O
for	O
a	O
long	O
compile	B-Language
process	O
before	O
being	O
informed	O
of	O
errors	O
.	O
</s>
<s>
One	O
downside	O
to	O
this	O
type	O
of	O
incremental	B-Application
compiler	I-Application
is	O
that	O
it	O
cannot	O
easily	O
optimize	O
the	O
code	O
that	O
it	O
compiles	B-Language
,	O
due	O
to	O
locality	O
and	O
the	O
limited	O
scope	O
of	O
what	O
is	O
changed	O
.	O
</s>
<s>
This	O
is	O
usually	O
not	O
a	O
problem	O
,	O
because	O
for	O
optimization	O
is	O
usually	O
only	O
carried	O
out	O
on	O
release	O
,	O
an	O
incremental	B-Application
compiler	I-Application
would	O
be	O
used	O
throughout	O
development	O
,	O
and	O
a	O
standard	O
batch	O
compiler	B-Language
would	O
be	O
used	O
on	O
release	O
.	O
</s>
<s>
In	O
the	O
interactive	B-Application
programming	I-Application
paradigm	O
,	O
e.g.	O
</s>
<s>
in	O
Poplog	B-Language
related	O
literature	O
,	O
and	O
an	O
interactive	O
compiler	B-Language
refers	O
to	O
a	O
compiler	B-Language
that	O
is	O
actually	O
a	O
part	O
of	O
the	O
runtime	B-Device
system	I-Device
of	O
the	O
source	O
language	O
.	O
</s>
<s>
The	O
compiler	B-Language
can	O
be	O
invoked	O
at	O
runtime	O
on	O
some	O
source	O
code	O
or	O
data	O
structure	O
managed	O
by	O
the	O
program	O
,	O
which	O
then	O
produces	O
a	O
new	O
compiled	B-Language
program	O
fragment	O
containing	O
machine	B-Language
code	I-Language
that	O
is	O
then	O
immediately	O
available	O
for	O
use	O
by	O
the	O
runtime	B-Device
system	I-Device
.	O
</s>
<s>
If	O
the	O
newly	O
compiled	B-Language
fragment	O
replaces	O
a	O
previous	O
compiled	B-Language
procedure	O
the	O
old	O
one	O
will	O
be	O
garbage	B-General_Concept
collected	I-General_Concept
.	O
</s>
<s>
This	O
scheme	B-Language
allows	O
for	O
a	O
degree	O
of	O
self-modifying	B-Application
code	I-Application
and	O
requires	O
metaprogramming	B-Application
language	O
features	O
.	O
</s>
<s>
The	O
ability	O
to	O
add	O
,	O
remove	O
and	O
delete	O
code	O
while	O
running	O
is	O
known	O
as	O
hot	B-Device
swapping	I-Device
.	O
</s>
<s>
Some	O
interactive	B-Application
programming	I-Application
platforms	O
mix	O
the	O
use	O
of	O
interpreted	O
and	O
compiled	B-Language
code	O
to	O
achieve	O
the	O
illusion	O
that	O
any	O
changes	O
to	O
code	O
are	O
accessible	O
by	O
the	O
program	O
immediately	O
.	O
</s>
<s>
The	O
PECAN	O
Programming	B-Application
Environment	I-Application
Generator	O
was	O
an	O
incremental	B-Application
compiler	I-Application
,	O
developed	O
by	O
Steven	O
P	O
.	O
Reiss	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
The	O
Gradle	B-Language
build	O
tool	O
has	O
supported	O
incremental	O
Java	B-Language
compilation	B-Language
since	O
version	O
2.1	O
.	O
</s>
<s>
Versions	O
of	O
Lisp	B-Language
:	O
</s>
<s>
Versions	O
of	O
Scheme	B-Language
:	O
</s>
<s>
Versions	O
of	O
Prolog	B-Language
:	O
</s>
<s>
Versions	O
of	O
ML	B-Language
:	O
</s>
