https://github.com/jaredly/let-anything

Deprecated, use the reasonml-community one
https://github.com/jaredly/let-anything

Last synced: about 2 months ago
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Deprecated, use the reasonml-community one

• Host: GitHub
• URL: https://github.com/jaredly/let-anything
• Owner: jaredly
• Created: 2018-09-05T06:14:54.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2019-11-20T16:36:18.000Z (over 4 years ago)
• Last Synced: 2024-05-05T03:22:54.012Z (about 2 months ago)
• Language: OCaml
• Homepage: https://github.com/reasonml-community/let-anything
• Size: 45.9 KB
• Stars: 99
• Watchers: 6
• Forks: 6
• Open Issues: 4
• Metadata Files:
  • Readme: Readme.md

Lists

• awesome-list - let-anything - community one | jaredly | 100 | (OCaml)
• awesome-ppx-reasonml - let-anything - Let%Anything ppx for async/options/results/etc (PPXs)

README

        
# Deprecated, use the [reasonml-community](https://github.com/reasonml-community/let-anything) one

# let%Anything

This is a ppx that looks for `let%Anything`, where Anything is a valid module identifier (e.g. captialized), and turns it into `Anything.let_(value, pattern => continuation)`.

It's an exploration of [this PR to the reason repo](https://github.com/facebook/reason/pull/2140).

Here's an example of using it ([source](https://github.com/notablemind/renm/blob/949e1583d4df5e6d61ea066767a52828f8f8069b/src/core/Store.re#L116

))

```re

let%Opt node = get(store, id);

let%Opt parent = get(store, node.parent);

Some((

  [NodeChildren(parent.id, parent.children |. List.keep((!=)(node.id))), DeleteNode(node.id),

  View({...store.view, active: nextId})

  ],

  [Event.Node(parent.id), Event.View(Node(nextId))]

))

```

### try%Anything

Let's make a `try_` function for the `result` type that does a *bind* over the error case:

```

module Res = {

  let try_ = (result, handler) => switch result {

    | Ok(v) => Ok(v)

    | Error(e) => handler(e)

  }

}

```

This will come in handy for the case where we want to transform the error side of a result -- either turning it into a different error type, or turning it into a successful value. For example:

```

let v = Error("bad")

try%Res v {

  | "invalid username/password" => Error(UserError)

  | "no user - use default" => Ok(defaultUser)

  | message => Error(ServerError)

}

```

#### In the general case

If you have a data type that has a "failure" case (like promises, or the `result` type), the `try%Anything` syntax can be helpful.

Here's the transform:

```

try%Blah someExpr {

  | Something(x) => y

}

```

becomes

```

Blah.try_(someExpr, result => switch result {

  | Something(x) => y

})

```

## Addendum

And here are the modules used ([source](https://github.com/notablemind/renm/blob/949e1583d4df5e6d61ea066767a52828f8f8069b/src/utils/Lets.re))

```re

module Opt = {

  let let_ = (a, b) => switch (a) {

    | None => None

    | Some(x) => b(x)

  }

};

module Result = {

  let let_ = (value, fn) => switch value {

    | Ok(v) => fn(v)

    | Error(_) => value

  };

  let try_ = (value, fn) => switch value {

    | Ok(_) => value

    | Error(err) => fn(err)

  };

}

```

# Usage

1. Install the NPM package `let-anything` through your favorite `npm` package manager (npm itself or yarn for example)

2. Add the following path to the `ppx-flags` defined in your `bsconfig.json` file (see bucklescript.github.io/bucklescript/docson/#build-schema.json): `let-anything/lib/bs/native/let_anything.native`