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spion/removed-resolve.md

Last active Aug 29, 2015
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What would you like to do?

Decision to remove resolve

Not sure if this is correct, but: This might actually be (perhaps accidentally) one step closer to allowing promises for thenables in a cleaner way if the need arises in the future.

Since its impossible to create a promise for a promise now, it would be theoretically possible to just

  • introduce Promise.of (wraps thenables)
  • make .then unwrap "true" promises only once
  • make resolve cast thenables into promises that recursively unwrap thenables

and be done.� You'd have

  • Promise.of - wraps thenables, returns promises, wraps other values
  • resolve - converts thenables to recursively unwrapping promises, returns promises, wraps other values
  • .then(f, r) - for values returned by the handlers: recursively unwraps thenables, unwraps promises once, wraps other values

After that, you could use .then in a monadic way, provided you remember to protect thenables with Promise.of (should not be a problem with typed compile-to-js languages). e.g. resolve(Promise.of(thenable)) or p.then(x => Promise.of(thenable)) You could also implement .map using .then and Promise.of

Previously you'd have to make resolve and Promise.cast the same before making .then unwrap a single level. Alternatively, you'd have to introduce .chain and have a confusingly dual API (chain/then, resolve/cast).

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