# ➗0️⃣❓ Check Maybe Div By Zero for Gleam
[](https://hex.pm/packages/gond)
[](https://www.erlang.org/)
[](https://en.wikipedia.org/wiki/JavaScript)
[](https://hexdocs.pm/gond/)
[](https://discord.gg/Fm8Pwmy)
**Gleam does not crash on division by zero.**
In effect any literal division by zero in Gleam returns a `0`. You may opt to
use Gleam stdlib's `int.divide`, `int.modulo`, `int.remainder`, `float.divide`
and `float.modulo` to catch errors instead of assuming `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 utility do
This helper checks Gleam code for potential(!) literal division by zero.
1. It may be 100% fine to run `1 / a` if you know that `a` is never zero.
2. It may also be fine to run `1 / a` where `a` equals `0` depending on your
logical requirements.
3. This checker is for when this is not fine. It allows you to check a code
repository for POTENTIAL literal division by zero in Gleam-land (it does NOT
check Erlang or JS FFI).
### Caveats
- No checks in Erlang, Elixir, JavaScript, or TypeScript FFI-land.
- This checker may detect false positives where your business code makes certain
for variable divisors to not be binding to zero.
- It also, so far, does not replace divisor constants but assumes that they are
variables. PRs are welcome.
## Installation
```sh
gleam add check_maybe_div_by_zero@1
```
## Local usage
It is recommended to add this checker to your CI.
```sh
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 division by zero is found.
```yaml
jobs:
test-and-no-div-zero:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: erlef/setup-beam@v1
with:
otp-version: "28.5"
gleam-version: "1.16.0"
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 / Bun / etc.
## Development
```sh
gleam test # Run the tests on Erlang
gleam test --target javascript # Run the tests on JavaScript
```
