bigi

Arbitrary precision integer arithmetic for Gleam.

In the Erlang target, all integers are automatically “big integers” that are subject to arbitrary precision arithmetic. This means there is no need for this package if you are only targeting Erlang.

In JavaScript, Gleam’s Int type corresponds to the number type, which is implemented using floating-point arithmetic. That means it’s subject to the following limits:

• Maximum safe integer and minimum safe integer beyond which the accuracy of arithmetic suffers, and
• maximum value and minimum value beyond which the numbers are converted to Infinity or -Infinity.

This package thus provides big integers for the JavaScript target and additionally provides a consistent interface for packages that target both Erlang and JavaScript. In Erlang, regular integers are used. In JavaScript, the BigInt type is used.

gleam add bigi

import bigi

pub fn main() {
  bigi.power(
    bigi.from_int(2),
    bigi.from_int(65_535)
  )

  // Ok(1001764965203423232489536175780127875223912737784875709632508486855447029778...)
}

Further documentation can be found at https://hexdocs.pm/bigi.

Limitations

Erlang does have a limit for big integers at around 4 megabits, as demonstrated below:

import bigi

pub fn main() {
  // Works
  bigi.power(bigi.from_int(2), bigi.from_int(4_194_239))

  // Blows up
  bigi.power(bigi.from_int(2), bigi.from_int(4_194_240))
}

For Node.js, the limit is somewhere higher.

bigi has no facilities to warn about or handle errors due to these system limits. It is up to the developer to be mindful of them.

Development

gleam run   # Run the project
gleam test  # Run the tests
gleam shell # Run an Erlang shell