optint
This library provides two new integer types, Optint.t
and Int63.t
, which
guarantee efficient representation on 64-bit architectures and provide a
best-effort boxed representation on 32-bit architectures.
Goal
The standard Int32.t
and Int64.t
types provided by the standard library have
the same heap-allocated representation on all architectures. This consistent
representation has costs in both memory and run-time performance.
On 64-bit architectures, it's often more efficient to use the native int
directly.
This library provides types to do exactly this:
Optint.t
: an integer containing at least 32 bits. On 64-bit, this is an
immediate integer; on 32-bit, it is a boxed 32-bit value. The overflow
behaviour is platform-dependent.Int63.t
: an integer containing exactly 63 bits. On 64-bit, this is an
immediate integer; on 32-bit, it is a boxed 64-bit integer that is wrapped to
provide 63-bit two's complement semantics. The two implementations are
observationally equivalent, modulo use ofMarshal
andObj
.
In summary:
| Integer type | 32-bit representation | 64-bit representation | Semantics |
| -- | -- | -- | -- |
| Stdlib.Int.t
| 31-bit immediate ✅ | 63-bit immediate ✅ | Always immediate |
| Stdlib.Nativeint.t
| 32-bit boxed ❌ | 64-bit boxed ❌ | Exactly word size |
| Stdlib.Int32.t
| 32-bit boxed ❌ | 32-bit boxed ❌ | Exactly 32 bits |
| Stdlib.Int64.t
| 64-bit boxed ❌ | 64-bit boxed ❌ | Exactly 64 bits |
| Optint.t
(new) | 32-bit boxed ❌ | 63-bit immediate ✅ | At least 32 bits |
| Int63.t
(new) | 64-bit boxed ❌ | 63-bit immediate ✅ | Exactly 63 bits |
These new types are safe and well-tested, but their architecture-dependent
implementation makes them unsuitable for use with the Marshal
module. Use the
provided encode and decode functions instead.
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>= "0.3.1"
>= "0.8"
>= "3.0.0"
>= "1.4.0"
>= "1.4.0"
>= "2.7.0"
>= "0.5.0"
>= "0.2.0"
>= "0.5.0"
< "1.0.0" | >= "1.3.0"