<s>
A	O
hash	B-Data_Structure
array	I-Data_Structure
mapped	I-Data_Structure
trie	I-Data_Structure
(	O
HAMT	O
)	O
is	O
an	O
implementation	O
of	O
an	O
associative	B-Application
array	I-Application
that	O
combines	O
the	O
characteristics	O
of	O
a	O
hash	B-Algorithm
table	I-Algorithm
and	O
an	O
array	O
mapped	O
trie	O
.	O
</s>
<s>
It	O
is	O
a	O
refined	O
version	O
of	O
the	O
more	O
general	O
notion	O
of	O
a	O
hash	B-Application
tree	I-Application
.	O
</s>
<s>
The	O
hash	B-Data_Structure
array	I-Data_Structure
mapped	I-Data_Structure
trie	I-Data_Structure
achieves	O
almost	O
hash	O
table-like	O
speed	O
while	O
using	O
memory	O
much	O
more	O
economically	O
.	O
</s>
<s>
Also	O
,	O
a	O
hash	B-Algorithm
table	I-Algorithm
may	O
have	O
to	O
be	O
periodically	O
resized	O
,	O
an	O
expensive	O
operation	O
,	O
whereas	O
HAMTs	O
grow	O
dynamically	O
.	O
</s>
<s>
The	O
programming	O
languages	O
Clojure	B-Language
,	O
Scala	B-Application
,	O
and	O
Frege	O
use	O
a	O
persistent	B-Application
variant	O
of	O
hash	B-Data_Structure
array	I-Data_Structure
mapped	I-Data_Structure
tries	I-Data_Structure
for	O
their	O
native	O
hash	B-Algorithm
map	I-Algorithm
type	O
.	O
</s>
<s>
The	O
Haskell	B-Language
library	O
"	O
unordered-containers	O
"	O
uses	O
the	O
same	O
to	O
implement	O
persistent	B-Application
map	O
and	O
set	O
data	O
structures	O
.	O
</s>
<s>
Another	O
Haskell	B-Language
library	O
"	O
stm-containers	O
"	O
adapts	O
the	O
algorithm	O
for	O
use	O
in	O
the	O
context	O
of	O
software	B-Operating_System
transactional	I-Operating_System
memory	I-Operating_System
.	O
</s>
<s>
A	O
Javascript	B-Language
HAMT	O
library	O
based	O
on	O
the	O
Clojure	B-Language
implementation	O
is	O
also	O
available	O
.	O
</s>
<s>
The	O
Rubinius	B-Application
implementation	O
of	O
Ruby	B-Language
includes	O
a	O
HAMT	O
,	O
mostly	O
written	O
in	O
Ruby	B-Language
but	O
with	O
3	O
primitives	O
.	O
</s>
<s>
Large	O
maps	O
in	O
Erlang	B-Operating_System
use	O
a	O
persistent	B-Application
HAMT	O
representation	O
internally	O
since	O
release	O
18.0	O
.	O
</s>
<s>
The	O
Pony	O
programming	O
language	O
uses	O
a	O
HAMT	O
for	O
the	O
hash	B-Algorithm
map	I-Algorithm
in	O
its	O
persistent	B-Application
collections	O
package	O
.	O
</s>
<s>
The	O
im	O
and	O
im-rc	O
crates	O
,	O
which	O
provide	O
persistent	B-Application
collection	O
types	O
for	O
the	O
Rust	O
programming	O
language	O
,	O
use	O
a	O
HAMT	O
for	O
their	O
persistent	B-Application
hash	B-Algorithm
tables	I-Algorithm
and	O
hash	O
sets	O
.	O
</s>
<s>
The	O
concurrent	O
lock-free	B-Operating_System
version	O
of	O
the	O
hash	O
trie	O
called	O
Ctrie	B-Algorithm
is	O
a	O
mutable	O
thread-safe	O
implementation	O
which	O
ensures	O
progress	O
.	O
</s>
<s>
The	O
data-structure	O
has	O
been	O
proven	O
to	O
be	O
correct	O
-	O
Ctrie	B-Algorithm
operations	O
have	O
been	O
shown	O
to	O
have	O
the	O
atomicity	B-General_Concept
,	O
linearizability	B-General_Concept
and	O
lock-freedom	B-Operating_System
properties	O
.	O
</s>
