Check Maybe Div By Zero for Gleam

Gleam does not crash on division by zero.

In effect any literal division by zero in gleam returns a zero. You may opt to use the stdlib’s int.divide, int.modulo, int.remainder, float.divide and float.modulo to catch errors instead of assmuing 0.

See following explanations why and what happens:

• https://tutorial.ponylang.io/gotchas/divide-by-zero.html
• https://www.hillelwayne.com/post/divide-by-zero/

What does this do

This helper checks gleam code for potential(!) literal division by zero. It may be 100% fine to run 1 / a if you know that a is never zero. It may also be fine to run 1 / a where a equals 0 depending on your requirements.

This checker is for when this is not fine. It allows you to check a code repository for POTENTIAL literal divison by zero in gleam-land (it does NOT check Erlang or JS FFI).

Installation

gleam add check_maybe_div_by_zero@1

Usage

gleam run --module check_maybe_div_by_zero
# or explicitly define the src dir to check:
gleam run --module check_maybe_div_by_zero -- src

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

CI Integration

You may run gleam run --module check_maybe_div_by_zero which returns exit(0) if no potential division by zero is found, and exit(1) if a potential division by zero is found. It should thus stop the CI in case a divison by zero is found.

jobs:
  test-and-no-div-zero:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: erlef/setup-beam@v1
        with:
          otp-version: "27.0.1"
          gleam-version: "1.3.2"
          rebar3-version: "3"
      - run: gleam deps download
      - run: gleam format --check src test
      - run: gleam test
      - run: gleam run --module check_maybe_div_by_zero -- src
      - run: gleam test --target javascript
      - run: gleam run --module check_maybe_div_by_zero --target javascript -- src

Targets

• Erlang
• NodeJS
• Deno

Development

gleam test  # Run the tests