https://github.com/hojberg/sums-up

SumTypes in TypeScript
https://github.com/hojberg/sums-up

adt fp functional-programming javascript typescript

Last synced: 3 months ago
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SumTypes in TypeScript

• Host: GitHub
• URL: https://github.com/hojberg/sums-up
• Owner: hojberg
• Created: 2018-09-03T21:26:37.000Z (over 6 years ago)
• Default Branch: main
• Last Pushed: 2023-01-05T10:13:59.000Z (about 2 years ago)
• Last Synced: 2024-04-13T16:20:36.942Z (9 months ago)
• Topics: adt, fp, functional-programming, javascript, typescript
• Language: TypeScript
• Size: 951 KB
• Stars: 28
• Watchers: 3
• Forks: 2
• Open Issues: 10
• Metadata Files:
  • Readme: README.md

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README

        
👍 Sums Up

===

### Installation

```

npm install sums-up

```

### Example

In TypeScript:

```typescript

import SumType from 'sums-up';

class Maybe extends SumType<{ Just: [T]; Nothing: [] }> {}

function Just(value: T): Maybe {

  return new Maybe("Just", value);

}

function Nothing(): Maybe {

  return new Maybe("Nothing");

}

const x = Just("foo");

const result = x.caseOf({

  Nothing: () => "nope",

  Just: (a) => a + "bar",

});

```

Or in JavaScript

```javascript

import SumType from 'sums-up';

class Maybe extends SumType {}

function Just(value) {

  return new Maybe("Just", value);

}

function Nothing() {

  return new Maybe("Nothing");

}

const x = Just("foo");

const result = x.caseOf({

  Nothing: () => "nope",

  Just: (a) => a + "bar",

});

```

### Wildcard Matching

If the kind of a sum type instance isn't present in the pattern given to `caseOf`, a default key called `_` will be used instead.

```ts

import SumType from 'sums-up';

class RequestState extends SumType<{

  NotStarted: [];

  Connecting: [];

  Downloading: [number];

  Completed: [T];

  Failed: [string];

}> {}

const state = new RequestState('Failed', 'Connection reset.');

const progressPercentage = state.caseOf({

  Downloading: pct => pct,

  Completed: () => 100,

  _: () => 0

});

```

Contributors: 

@hojberg @dfreeman @AdamEdgett