<s>
Vala	B-Language
is	O
an	O
object-oriented	B-Language
programming	I-Language
language	I-Language
with	O
a	O
self-hosting	O
compiler	O
that	O
generates	O
C	B-Language
code	O
and	O
uses	O
the	O
GObject	B-Language
system	O
.	O
</s>
<s>
Vala	B-Language
is	O
syntactically	O
similar	O
to	O
C#	B-Application
and	O
includes	O
notable	O
features	O
such	O
as	O
anonymous	B-General_Concept
functions	I-General_Concept
,	O
signals	B-Application
,	O
properties	B-Language
,	O
generics	B-Language
,	O
assisted	B-General_Concept
memory	I-General_Concept
management	I-General_Concept
,	O
exception	B-General_Concept
handling	I-General_Concept
,	O
type	O
inference	O
,	O
and	O
foreach	O
statements	O
.	O
</s>
<s>
Its	O
developers	O
,	O
Jürg	O
Billeter	O
and	O
Raffaele	O
Sandrini	O
,	O
wanted	O
to	O
bring	O
these	O
features	O
to	O
the	O
plain	O
C	B-Language
runtime	B-Device
with	O
little	O
overhead	O
and	O
no	O
special	O
runtime	B-Device
support	O
by	O
targeting	O
the	O
GObject	B-Language
object	B-Language
system	I-Language
.	O
</s>
<s>
It	O
source-to-source	B-Language
compiles	I-Language
to	O
C	B-Language
,	O
which	O
is	O
then	O
compiled	O
with	O
a	O
C	B-Language
compiler	O
for	O
a	O
given	O
platform	O
,	O
such	O
as	O
GCC	B-Application
or	O
Clang	B-Application
.	O
</s>
<s>
Using	O
functionality	O
from	O
native	O
code	B-Library
libraries	I-Library
requires	O
writing	O
vapi	O
files	O
,	O
defining	O
the	O
library	O
interfaces	B-Application
.	O
</s>
<s>
Writing	O
these	O
interface	O
definitions	O
is	O
well-documented	O
for	O
C	B-Language
libraries	B-Library
,	O
especially	O
when	O
based	O
on	O
GObject	B-Language
.	O
</s>
<s>
Bindings	O
are	O
already	O
available	O
for	O
a	O
large	O
number	O
of	O
libraries	B-Library
,	O
including	O
for	O
C	B-Language
libraries	B-Library
that	O
are	O
not	O
based	O
on	O
GObject	B-Language
,	O
such	O
as	O
the	O
multimedia	O
library	O
SDL	B-Operating_System
,	O
OpenGL	B-Application
,	O
etc	O
.	O
</s>
<s>
Vala	B-Language
is	O
a	O
programming	O
language	O
that	O
combines	O
the	O
high-level	B-Language
build-time	O
performance	O
of	O
scripting	O
languages	O
with	O
the	O
run-time	O
performance	O
of	O
low-level	B-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
It	O
aims	O
to	O
bring	O
modern	O
programming	O
language	O
features	O
to	O
GNOME	B-Application
developers	O
without	O
imposing	O
any	O
additional	O
runtime	B-Device
requirements	O
and	O
without	O
using	O
a	O
different	O
ABI	B-Operating_System
,	O
compared	O
to	O
applications	O
and	O
libraries	B-Library
written	O
in	O
C	B-Language
.	O
The	O
syntax	O
of	O
Vala	B-Language
is	O
similar	O
to	O
C#	B-Application
,	O
modified	O
to	O
better	O
fit	O
the	O
GObject	B-Language
type	O
system	O
.	O
</s>
<s>
Vala	B-Language
was	O
conceived	O
by	O
Jürg	O
Billeter	O
and	O
was	O
implemented	O
by	O
him	O
and	O
Raffaele	O
Sandrini	O
,	O
who	O
wished	O
for	O
a	O
higher	O
level	O
alternative	O
for	O
developing	O
GNOME	B-Application
applications	O
instead	O
of	O
C	B-Language
.	O
They	O
did	O
like	O
the	O
syntax	O
and	O
semantics	O
of	O
C#	B-Application
but	O
did	O
not	O
want	O
to	O
use	O
Mono	B-Application
,	O
so	O
they	O
finished	O
a	O
compiler	O
in	O
May	O
2006	O
.	O
</s>
<s>
Initially	O
,	O
it	O
was	O
bootstrapped	B-Application
using	O
C	B-Language
,	O
and	O
one	O
year	O
later	O
(	O
with	O
release	O
of	O
version	O
0.1.0	O
in	O
July	O
2007	O
)	O
,	O
the	O
Vala	B-Language
compiler	O
became	O
self-hosted	O
.	O
</s>
<s>
Vala	B-Language
uses	O
GLib	B-Language
and	O
its	O
submodules	O
(	O
GObject	B-Language
,	O
GModule	O
,	O
GThread	O
,	O
GIO	O
)	O
as	O
the	O
core	O
library	O
,	O
which	O
is	O
available	O
for	O
most	O
operating	B-General_Concept
systems	I-General_Concept
and	O
offers	O
things	O
like	O
platform	B-Operating_System
independent	I-Operating_System
threading	B-Operating_System
,	O
input/output	B-Operating_System
,	O
file	B-Application
management	I-Application
,	O
network	B-Protocol
sockets	I-Protocol
,	O
plugins	B-Operating_System
,	O
regular	B-Language
expressions	I-Language
,	O
etc	O
.	O
</s>
<s>
The	O
syntax	O
of	O
Vala	B-Language
currently	O
supports	O
modern	O
language	O
features	O
as	O
follows	O
:	O
</s>
<s>
Graphical	B-Application
user	I-Application
interfaces	I-Application
can	O
be	O
developed	O
with	O
the	O
GTK	B-Application
GUI	B-Library
toolkit	I-Library
and	O
the	O
Glade	B-Language
GUI	B-Application
builder	O
.	O
</s>
<s>
For	O
memory	O
management	O
,	O
the	O
GType	B-Language
or	O
GObject	B-Language
system	O
provides	O
reference	B-General_Concept
counting	I-General_Concept
.	O
</s>
<s>
In	O
C	B-Language
,	O
a	O
programmer	O
must	O
manually	O
manage	O
adding	O
and	O
removing	O
references	O
,	O
but	O
in	O
Vala	B-Language
,	O
managing	O
such	O
reference	B-General_Concept
counts	I-General_Concept
is	O
automated	O
if	O
a	O
programmer	O
uses	O
the	O
language	O
's	O
built-in	O
reference	O
types	O
rather	O
than	O
plain	O
pointers	O
.	O
</s>
<s>
Vala	B-Language
also	O
allows	O
manual	O
memory	O
management	O
with	O
pointers	O
as	O
an	O
option	O
.	O
</s>
<s>
Vala	B-Language
is	O
intended	O
to	O
provide	O
runtime	B-Device
access	O
to	O
existing	O
C	B-Language
libraries	B-Library
,	O
especially	O
GObject-based	O
libraries	B-Library
,	O
without	O
the	O
need	O
for	O
runtime	B-Device
bindings	O
.	O
</s>
<s>
To	O
use	O
a	O
library	O
with	O
Vala	B-Language
,	O
all	O
that	O
needed	O
is	O
an	O
API	O
file	O
(	O
.vapi	B-Language
)	O
containing	O
the	O
class	O
and	O
method	O
declarations	O
in	O
Vala	B-Language
syntax	O
.	O
</s>
<s>
However	O
,	O
C++	B-Language
libraries	B-Library
are	O
not	O
supported	O
.	O
</s>
<s>
At	O
present	O
,	O
vapi	O
files	O
for	O
a	O
large	O
part	O
of	O
the	O
GNU	B-Operating_System
project	O
and	O
GNOME	B-Application
platform	O
are	O
included	O
with	O
each	O
release	O
of	O
Vala	B-Language
,	O
including	O
GTK	B-Application
.	O
</s>
<s>
There	O
is	O
also	O
a	O
library	O
called	O
Gee	O
,	O
written	O
in	O
Vala	B-Language
,	O
that	O
provides	O
GObject-based	O
interfaces	B-Application
and	O
classes	O
for	O
commonly	O
used	O
data	B-General_Concept
structures	I-General_Concept
.	O
</s>
<s>
It	O
should	O
also	O
be	O
easily	O
possible	O
to	O
write	O
a	O
bindings	O
generator	O
for	O
access	O
to	O
Vala	B-Language
libraries	B-Library
from	O
applications	O
written	O
in	O
other	O
languages	O
,	O
e.g.	O
,	O
C#	B-Application
,	O
as	O
the	O
Vala	B-Language
parser	O
is	O
written	O
as	O
a	O
library	O
,	O
so	O
that	O
all	O
compile-time	O
information	O
is	O
available	O
when	O
generating	O
a	O
binding	O
.	O
</s>
<s>
Tooling	O
for	O
Vala	B-Language
development	O
has	O
seen	O
significant	O
improvement	O
over	O
the	O
recent	O
years	O
.	O
</s>
<s>
The	O
following	O
is	O
a	O
list	O
of	O
some	O
popular	O
IDEs	O
and	O
text	O
editors	O
with	O
plug-ins	O
that	O
add	O
support	O
for	O
programming	O
in	O
Vala	B-Language
:	O
</s>
<s>
Currently	O
,	O
there	O
are	O
two	O
actively	O
developing	O
language	O
servers	O
which	O
offer	O
code	B-Application
intelligence	I-Application
for	O
Vala	B-Language
as	O
follows	O
:	O
</s>
<s>
Currently	O
,	O
there	O
are	O
a	O
number	O
of	O
build	B-Application
systems	I-Application
supporting	O
Vala	B-Language
,	O
including	O
Automake	B-Application
,	O
CMake	B-Language
,	O
Meson	B-Application
,	O
and	O
others	O
.	O
</s>
<s>
Debugging	O
for	O
Vala	B-Language
programs	O
can	O
be	O
done	O
with	O
either	O
GDB	B-Language
or	O
LLDB	B-Language
.	O
</s>
<s>
GNOME	B-Language
Builder	I-Language
has	O
built-in	O
debugging	O
support	O
for	O
Vala	B-Language
with	O
GDB	B-Language
.	O
</s>
<s>
Visual	B-Language
Studio	I-Language
Code	I-Language
has	O
extensions	O
for	O
GDB	B-Language
and	O
LLDB	B-Language
,	O
such	O
as	O
cpptools	O
and	O
CodeLLDB	O
.	O
</s>
<s>
program	O
in	O
Vala	B-Language
:	O
</s>
<s>
As	O
can	O
be	O
noted	O
,	O
unlike	O
C	B-Language
or	O
C++	B-Language
,	O
there	O
are	O
no	O
header	O
files	O
in	O
Vala	B-Language
.	O
</s>
<s>
The	O
linking	O
to	O
libraries	B-Library
is	O
done	O
by	O
specifying	O
--pkg	O
parameters	O
during	O
compiling	O
.	O
</s>
<s>
Moreover	O
,	O
the	O
GLib	B-Language
library	O
is	O
always	O
linked	O
and	O
its	O
namespace	O
can	O
be	O
omitted	O
(	O
print	O
is	O
in	O
fact	O
GLib.print	O
)	O
.	O
</s>
<s>
Below	O
is	O
a	O
more	O
complex	O
version	O
which	O
defines	O
a	O
subclass	O
HelloWorld	O
inheriting	O
from	O
the	O
base	O
class	O
GLib.Object	B-Language
,	O
aka	O
the	O
GObject	B-Language
class	O
.	O
</s>
<s>
It	O
shows	O
some	O
of	O
Vala	B-Language
's	O
object-oriented	B-Language
features	O
:	O
</s>
<s>
As	O
in	O
the	O
case	O
of	O
GObject	B-Language
library	O
,	O
Vala	B-Language
does	O
not	O
support	O
multiple	B-Application
inheritance	I-Application
,	O
but	O
a	O
class	O
in	O
Vala	B-Language
can	O
implement	O
any	O
number	O
of	O
interfaces	B-Application
,	O
which	O
may	O
contain	O
default	O
implementations	O
for	O
their	O
methods	O
.	O
</s>
<s>
Below	O
is	O
a	O
basic	O
example	O
to	O
show	O
how	O
to	O
define	O
a	O
signal	O
in	O
a	O
class	O
that	O
is	O
not	O
compact	O
,	O
which	O
has	O
a	O
signal	O
system	O
built	O
in	O
by	O
Vala	B-Language
through	O
GLib	B-Language
.	O
</s>
<s>
A	O
new	O
thread	B-Operating_System
in	O
Vala	B-Language
is	O
a	O
portion	O
of	O
code	O
such	O
as	O
a	O
function	O
that	O
is	O
requested	O
to	O
be	O
executed	O
concurrently	O
at	O
runtime	B-Device
.	O
</s>
<s>
The	O
creation	O
and	O
synchronization	O
of	O
new	O
threads	B-Operating_System
are	O
done	O
by	O
using	O
the	O
Thread	B-Operating_System
class	O
in	O
GLib	B-Language
,	O
which	O
takes	O
the	O
function	O
as	O
a	O
parameter	O
when	O
creating	O
new	O
threads	B-Operating_System
,	O
as	O
shown	O
in	O
the	O
following	O
(	O
very	O
simplified	O
)	O
example	O
:	O
</s>
<s>
Below	O
is	O
an	O
example	O
using	O
GTK	B-Application
to	O
create	O
a	O
GUI	B-Application
"	O
Hello	O
,	O
World	O
!	O
"	O
</s>
<s>
program	O
(	O
see	O
also	O
GTK	B-Application
hello	O
world	O
)	O
in	O
Vala	B-Language
:	O
</s>
<s>
The	O
statement	O
Gtk.main	O
(	O
)	O
creates	O
and	O
starts	O
a	O
main	B-General_Concept
loop	I-General_Concept
listening	O
for	O
events	O
,	O
which	O
are	O
passed	O
along	O
via	O
signals	B-Application
to	O
the	O
callback	O
functions	O
.	O
</s>
<s>
As	O
this	O
example	O
uses	O
the	O
GTK	B-Application
package	O
,	O
it	O
needs	O
an	O
extra	O
--pkg	O
parameter	O
(	O
which	O
invokes	O
pkg-config	B-Application
in	O
the	O
C	B-Language
backend	B-Architecture
)	O
to	O
compile	O
:	O
</s>
