https://github.com/jaredly/ppx_guard
early returns for ocaml/reason
https://github.com/jaredly/ppx_guard
Last synced: about 1 year ago
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early returns for ocaml/reason
- Host: GitHub
- URL: https://github.com/jaredly/ppx_guard
- Owner: jaredly
- Created: 2017-08-22T04:48:49.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2017-11-15T06:03:46.000Z (over 8 years ago)
- Last Synced: 2025-02-19T13:11:58.851Z (over 1 year ago)
- Language: OCaml
- Homepage:
- Size: 5.86 KB
- Stars: 4
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: Readme.md
Awesome Lists containing this project
README
# ppx_guard
`guard let` for reason/ocaml!
## What?
A shortcut for early returns when you know it's going south :P
```reason
let doit something => {
[%guard let Ok value = doAnAction something][@else None];
/* etc */
Some 10
}
/* becomes */
let doit something => {
switch (doAnAction something) {
| Ok value => Some 10
| _ => None
}
}
let multiple x y => {
[%guard let Some x = x][@else None];
let awesome = 10;
[%guard let Some y = y][@else None];
Some (x + y)
}
/* becomes */
let multiple x y => {
switch x {
| Some x => {
let awesome = 10;
switch y {
| Some y => Some (x + y)
| _ => None
}
}
| _ => None
}
}
```
## Related work / inspiration
Inspired by swift's [`guard let`](https://thatthinginswift.com/guard-statement-swift/), [`if let`, `if case`, `guard case`](http://alisoftware.github.io/swift/pattern-matching/2016/05/16/pattern-matching-4/), etc. It currently acts similar to swift's `guard case`.
It's also inspired by rust's [`try!` macro](https://doc.rust-lang.org/std/macro.try.html) (which is now deprecated in favor of a bit of syntax sugar, the `?` postfix operator, which does the same thing).
It might be interesting to add a `[%try` function, which would have the same
effect as rust's try macro. If we start to use `result` a lot, it could be
worth it.
## FAQ
#### Why not have it act only on `option` (as swift does with `guard let`)?
I considered that, but I think it might
not be as common as in swift. An alternative would be to have a `guard_case`
that does what this currently does, and then `guard` would be for unwrapping
optionals.