<s>
Mirah	B-Language
(	O
formerly	O
Duby	O
)	O
has	O
been	O
a	O
programming	O
language	O
based	O
on	O
Ruby	B-Language
language	I-Language
syntax	O
,	O
local	O
type	O
inference	O
,	O
hybrid	O
static	O
–	O
dynamic	O
type	O
system	O
,	O
and	O
a	O
pluggable	B-Application
compiler	O
toolchain	B-General_Concept
.	O
</s>
<s>
Mirah	B-Language
was	O
created	O
by	O
Charles	O
Oliver	O
Nutter	O
to	O
be	O
"	O
a	O
'	O
Ruby-like	O
'	O
language	O
,	O
probably	O
a	O
subset	O
of	O
Ruby	B-Language
syntax	O
,	O
that	O
 [ could ] 	O
compile	O
to	O
solid	O
,	O
fast	O
,	O
idiomatic	O
JVM	O
bytecode.	O
"	O
</s>
<s>
The	O
word	O
refers	O
to	O
the	O
gemstone	O
ruby	B-Language
in	O
the	O
Javanese	O
language	O
,	O
a	O
play	O
on	O
the	O
concept	O
of	O
Ruby	B-Language
in	O
Java	B-Language
.	O
</s>
<s>
To	O
foster	O
more	O
participation	O
in	O
the	O
JRuby	B-Language
project	O
from	O
Ruby	B-Language
community	O
members	O
,	O
Nutter	O
began	O
to	O
explore	O
the	O
possibility	O
of	O
presenting	O
Ruby	B-Language
syntax	O
,	O
but	O
with	O
a	O
static	O
type	O
model	O
and	O
direct-to-native	O
compiling	O
.	O
</s>
<s>
In	O
this	O
context	O
,	O
"	O
native	O
"	O
meant	O
mainly	O
the	O
Java	B-Language
virtual	I-Language
machine	I-Language
(	O
JVM	B-Language
)	O
,	O
but	O
Mirah	B-Language
has	O
been	O
designed	O
around	O
the	O
possibility	O
of	O
having	O
alternative	O
backends	B-Architecture
for	O
other	O
object-oriented	B-Language
runtimes	O
like	O
the	O
Common	O
Language	O
Runtime	O
(	O
CLR	O
)	O
of	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
The	O
language	O
needed	O
to	O
look	O
and	O
feel	O
like	O
Ruby	B-Language
,	O
and	O
to	O
introduce	O
no	O
new	O
library	O
dependencies	O
into	O
JRuby	B-Language
(	O
which	O
precludes	O
most	O
other	O
JVM	B-Language
languages	I-Language
)	O
and	O
to	O
suffer	O
no	O
performance	O
penalty	O
(	O
which	O
precludes	O
writing	O
in	O
Ruby	B-Language
)	O
.	O
</s>
<s>
Early	O
versions	O
of	O
Mirah	B-Language
(	O
then	O
Duby	O
)	O
focused	O
mostly	O
on	O
mathematical	O
performance	O
,	O
where	O
dynamic	B-Language
programming	I-Language
languages	I-Language
often	O
pay	O
the	O
highest	O
cost	O
.	O
</s>
<s>
Since	O
then	O
it	O
has	O
evolved	O
into	O
a	O
full	O
JVM	B-Language
language	I-Language
,	O
with	O
several	O
users	O
and	O
real-world	O
applications	B-Application
using	O
it	O
for	O
core	O
components	O
.	O
</s>
<s>
Mirah	B-Language
is	O
mostly	O
a	O
pluggable	B-Application
compiler	O
toolchain	B-General_Concept
.	O
</s>
<s>
This	O
makes	O
Mirah	B-Language
suitable	O
for	O
many	O
backends	B-Architecture
,	O
and	O
also	O
makes	O
it	O
possible	O
to	O
write	O
language	O
plug-ins	B-Application
for	O
Mirah	B-Language
's	O
transformation	O
phase	O
that	O
will	O
apply	O
to	O
all	O
supported	O
backends	B-Architecture
equally	O
.	O
</s>
<s>
For	O
simple	O
pieces	O
of	O
code	O
and	O
the	O
JVM	B-Language
bytecode	I-Language
backend	B-Architecture
,	O
the	O
Mirah	B-Language
compiler	O
emits	O
nearly	O
the	O
same	O
instructions	O
as	O
standard	O
javac	B-General_Concept
compilers	O
.	O
</s>
<s>
Because	O
Mirah	B-Language
is	O
just	O
a	O
compiler	O
,	O
it	O
ships	O
no	O
standard	B-Library
library	I-Library
.	O
</s>
<s>
The	O
intent	O
is	O
that	O
Mirah	B-Language
users	O
will	O
choose	O
what	O
libraries	O
they	O
want	O
to	O
use	O
,	O
perhaps	O
write	O
plugins	B-Application
for	O
the	O
Mirah	B-Language
compiler	O
to	O
support	O
them	O
,	O
and	O
the	O
compiler	O
will	O
do	O
the	O
rest	O
.	O
</s>
<s>
The	O
standard	B-Library
library	I-Library
for	O
Mirah	B-Language
,	O
then	O
,	O
is	O
whatever	O
the	O
standard	B-Library
library	I-Library
for	O
the	O
current	O
backend	B-Architecture
is	O
,	O
and	O
emphasis	O
is	O
placed	O
on	O
writing	O
compiler	O
plugins	B-Application
rather	O
than	O
libraries	O
to	O
extend	O
and	O
enhance	O
the	O
language	O
.	O
</s>
<s>
Mirah	B-Language
does	O
not	O
impose	O
a	O
specific	O
type	O
system	O
on	O
users	O
,	O
instead	O
relying	O
on	O
whatever	O
the	O
target	O
backend	B-Architecture
provides	O
.	O
</s>
<s>
On	O
the	O
JVM	B-Language
,	O
the	O
type	O
system	O
is	O
largely	O
Java	B-Language
's	O
type	O
system	O
,	O
and	O
type	O
declarations	O
refer	O
to	O
JVM	B-Language
classes	O
,	O
primitives	O
,	O
and	O
interfaces	O
.	O
</s>
<s>
Mirah	B-Language
is	O
primarily	O
a	O
statically-typed	O
language	O
,	O
but	O
support	O
is	O
in	O
development	O
to	O
allow	O
dynamic	O
typing	O
also	O
.	O
</s>
<s>
The	O
mechanism	O
is	O
similar	O
to	O
that	O
provided	O
in	O
C#	B-Application
4	O
,	O
with	O
a	O
special	O
dynamic	O
type	O
indicating	O
all	O
dispatches	O
against	O
that	O
variable	O
's	O
value	O
should	O
be	O
done	O
dynamically	O
.	O
</s>
<s>
Dynamic	O
type	O
support	O
is	O
currently	O
planned	O
only	O
for	O
Java	B-Language
7	O
and	O
higher	O
,	O
using	O
the	O
new	O
invokedynamic	O
bytecode	B-Language
.	O
</s>
<s>
The	O
syntax	O
of	O
Mirah	B-Language
is	O
largely	O
the	O
same	O
as	O
the	O
syntax	O
of	O
Ruby	B-Language
,	O
but	O
with	O
a	O
few	O
modifications	O
to	O
support	O
static	O
typing	O
:	O
</s>
<s>
Because	O
several	O
transformations	O
occur	O
in	O
the	O
Mirah	B-Language
compiler	O
toolchain	B-General_Concept
,	O
some	O
strings	O
that	O
are	O
valid	O
identifiers	O
in	O
Ruby	B-Language
are	O
treated	O
as	O
keywords	O
in	O
Mirah	B-Language
,	O
such	O
as	O
the	O
word	O
interface	O
used	O
to	O
specify	O
a	O
JVM-style	O
interface	O
.	O
</s>
<s>
Outside	O
of	O
these	O
differences	O
,	O
Mirah	B-Language
code	O
generally	O
looks	O
like	O
Ruby	B-Language
code	O
:	O
</s>
<s>
,	O
Mirah	B-Language
is	O
under	O
development	O
,	O
but	O
some	O
developers	O
are	O
using	O
Mirah	B-Language
for	O
production	O
applications	B-Application
of	O
limited	O
scope	O
.	O
</s>
<s>
Dubious	O
is	O
a	O
project	O
for	O
running	O
Mirah	B-Language
on	O
Google	B-Application
App	I-Application
Engine	I-Application
.	O
</s>
<s>
It	O
provides	O
a	O
way	O
to	O
build	O
apps	O
in	O
Mirah	B-Language
,	O
with	O
conventions	O
familiar	O
to	O
developers	O
using	O
Ruby	B-Application
on	I-Application
Rails	I-Application
and	O
Sinatra	B-Application
.	O
</s>
<s>
Since	O
everything	O
is	O
compiled	B-Application
ahead-of-time	I-Application
,	O
Mirah	B-Language
applications	B-Application
have	O
none	O
of	O
the	O
initializing	O
costs	O
associated	O
with	O
JRuby	B-Language
.	O
</s>
<s>
Dubious	O
supports	O
ERuby	B-Application
(	O
ERb	O
)	O
and	O
has	O
a	O
simple	O
datastore	O
adapter	O
that	O
uses	O
a	O
syntax	O
similar	O
to	O
Datamapper	B-Application
.	O
</s>
