<s>
Leo	B-Language
is	O
an	O
open-source	B-Application
text	O
editor/outliner	O
that	O
features	O
clones	O
(	O
virtual	O
copies	O
of	O
outline	O
nodes	O
)	O
as	O
a	O
central	O
tool	O
of	O
organization	O
,	O
navigation	O
,	O
customization	O
and	O
scripting	O
.	O
</s>
<s>
Leo	B-Language
can	O
manipulate	O
text	O
or	O
code	O
in	O
any	O
human	O
or	O
computer	O
programming	O
language	O
(	O
e.g.	O
,	O
Python	B-Language
,	O
C	O
,	O
C++	O
,	O
Java	O
)	O
,	O
as	O
Leo	B-Language
is	O
a	O
language-independent	O
or	O
"	O
adaptable	O
LPE	O
"	O
(	O
literate	B-Application
programming	I-Application
environment	O
)	O
.	O
</s>
<s>
Leo	B-Language
is	O
written	O
in	O
Python	B-Language
and	O
can	O
be	O
extended	O
with	O
plugins	O
written	O
in	O
Python	B-Language
.	O
</s>
<s>
The	O
GUI	O
uses	O
the	O
Qt	B-Language
toolkit	I-Language
;	O
the	O
syntax-aware	O
editor	O
is	O
based	O
on	O
Scintilla	B-Language
.	O
</s>
<s>
Leo	B-Language
outlines	O
are	O
stored	O
as	O
XML	B-Protocol
files	O
.	O
</s>
<s>
Leo	B-Language
's	O
foremost	O
functionality	O
,	O
in	O
addition	O
to	O
text	B-Application
editing	I-Application
,	O
is	O
that	O
of	O
an	O
outliner	B-Application
,	O
with	O
a	O
"	O
vast	O
range	O
of	O
convenience	O
features	O
for	O
structuring	O
and	O
managing	O
outlines	O
"	O
both	O
by	O
drag-and-drop	O
via	O
GUI	O
and	O
by	O
keyboard	O
commands	O
.	O
</s>
<s>
Leo	B-Language
's	O
outline	O
pane	O
shows	O
a	O
tree	B-Application
of	O
data	O
nodes	O
.	O
</s>
<s>
Leo	B-Language
trees	O
are	O
in	O
fact	O
directed	O
acyclic	O
graphs	O
;	O
nodes	O
may	O
have	O
more	O
than	O
one	O
parent	O
.	O
</s>
<s>
Leo	B-Language
calls	O
such	O
nodes	O
clones	O
.	O
</s>
<s>
When	O
saving	O
an	O
outline	O
Leo	B-Language
automatically	O
writes	O
all	O
changed	O
@file	O
trees	O
back	O
to	O
the	O
external	O
files	O
.	O
</s>
<s>
When	O
Leo	B-Language
reads	O
an	O
outline	O
,	O
these	O
comments	O
allow	O
Leo	B-Language
to	O
recreate	O
@file	O
trees	O
using	O
only	O
the	O
data	O
in	O
the	O
external	O
file	O
.	O
</s>
<s>
When	O
reading	O
@auto	O
nodes	O
,	O
Leo	B-Language
uses	O
the	O
program	O
structure	O
of	O
the	O
external	O
file	O
to	O
create	O
the	O
@auto	O
tree	B-Application
.	O
</s>
<s>
When	O
reading	O
@clean	O
nodes	O
,	O
Leo	B-Language
uses	O
the	O
structure	O
of	O
the	O
outline	O
to	O
create	O
the	O
@clean	O
tree	B-Application
.	O
</s>
<s>
Leo	B-Language
's	O
outline	O
or	O
hierarchical	O
structure	O
is	O
distinct	O
from	O
the	O
web	O
of	O
interleaved	O
program	O
and	O
documentation	O
"	O
chunks	O
"	O
associated	O
with	O
classic	O
literate	B-Application
programming	I-Application
tools	O
.	O
</s>
<s>
The	O
body	O
text	O
of	O
any	O
Leo	B-Language
node	O
may	O
contain	O
a	O
Leo	B-Language
script	O
,	O
a	O
Python	B-Language
script	I-Language
executed	O
in	O
the	O
context	O
of	O
a	O
Leo	B-Language
outline	O
.	O
</s>
<s>
A	O
simple	O
API	B-General_Concept
gives	O
Leo	B-Language
scripts	O
full	O
access	O
to	O
all	O
data	O
in	O
loaded	O
outlines	O
,	O
as	O
well	O
as	O
full	O
access	O
to	O
Leo	B-Language
's	O
own	O
source	O
code	O
.	O
</s>
<s>
The	O
API	B-General_Concept
includes	O
Python	B-Language
iterators	O
that	O
allow	O
scripts	O
to	O
traverse	O
outlines	O
easily	O
.	O
</s>
<s>
Scripts	O
may	O
be	O
composed	O
of	O
any	O
tree	B-Application
of	O
nodes	O
.	O
</s>
<s>
A	O
markup	O
language	O
similar	O
to	O
noweb	B-Application
tells	O
Leo	B-Language
how	O
to	O
create	O
scripts	O
from	O
(	O
parts	O
of	O
)	O
an	O
outline	O
.	O
</s>
<s>
Leo	B-Language
executes	O
the	O
script	O
of	O
an	O
@button	O
node	O
in	O
the	O
context	O
of	O
any	O
other	O
outline	O
node	O
.	O
</s>
