77 lines
2.5 KiB
Markdown
77 lines
2.5 KiB
Markdown
# bigi
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[](https://hex.pm/packages/bigi)
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[](https://hexdocs.pm/bigi/)
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Arbitrary precision integer arithmetic for Gleam.
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In the Erlang target, all integers are automatically "big integers" that are subject to
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arbitrary precision arithmetic. This means there is no need for this package if you are only
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targeting Erlang.
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In JavaScript, Gleam's `Int` type corresponds to the `number` type, which is implemented using
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floating-point arithmetic. That means it's subject to the following limits:
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- [Maximum safe integer](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER)
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and
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[minimum safe integer](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_SAFE_INTEGER)
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beyond which the accuracy of arithmetic suffers, and
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- [maximum value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_VALUE)
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and
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[minimum value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_VALUE)
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beyond which the numbers are converted to `Infinity` or `-Infinity`.
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This package thus provides big integers for the JavaScript target and additionally provides a
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consistent interface for packages that target both Erlang and JavaScript. In Erlang, regular
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integers are used. In JavaScript, the
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[`BigInt`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt)
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type is used.
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```sh
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gleam add bigi
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```
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```gleam
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import bigi
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pub fn main() {
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bigi.power(
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bigi.from_int(2),
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bigi.from_int(65_535)
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)
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// Ok(1001764965203423232489536175780127875223912737784875709632508486855447029778...)
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}
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```
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Further documentation can be found at <https://hexdocs.pm/bigi>.
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## Limitations
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Erlang does have [a limit for big integers at around 4 megabits](https://elixirforum.com/t/is-there-an-integer-size-limit/65647/8?u=nicd),
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as demonstrated below:
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```gleam
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import bigi
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pub fn main() {
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// Works
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bigi.power(bigi.from_int(2), bigi.from_int(4_194_239))
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// Blows up
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bigi.power(bigi.from_int(2), bigi.from_int(4_194_240))
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}
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```
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For Node.js, the limit is somewhere higher.
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`bigi` has no facilities to warn about or handle errors due to these system limits. It is up to the developer
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to be mindful of them.
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## Development
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```sh
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gleam run # Run the project
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gleam test # Run the tests
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gleam shell # Run an Erlang shell
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```
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