Add Result.prototype.filter and Maybe.prototype.filter

origamitower / folktale

[not actively maintained!] A standard library for functional programming in JavaScript

https://folktale.origamitower.com/

MIT License

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Add Result.prototype.filter and Maybe.prototype.filter #133

Closed floriansimon1 closed 7 years ago

floriansimon1 commented 7 years ago

The filter function should apply only on Oks (resp. Justs) and return an Error (resp. a Nothing) if the passed predicate is false, or return this otherwise.