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Stabilize core::convert::identity - #57322
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SimonSapin
commented
Jan 5, 2019
r+, pending FCP completion |
| @@ -86,14 +84,13 @@ | |||
| /// Using `identity` to keep the `Some` variants of an iterator of `Option<T>`: | |||
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I feel like this particularly would be better as flatten with an explicit specialisation for Option, rather than filter_map.
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I disagree.
First, I think that .filter_map(identity) is clearer wrt. intent (and also semantics). I can clearly tell that filtering is happening because it says so in the name. I know that .filter_map takes f: T -> Option<U> and with identity I fix T = Option<U> and thus I get back all the Somes. The .flatten() method doesn't tell me any of this, in particular you cannot tell without knowing that Option is being operated on what the semantics are. Thus the reasoning footprint is greater with .flatten().
Second, even tho .flatten() is more general than join :: Monad m => m (m a) -> m a I think the primary use of the method should be for monadic join and using it for other purposes will break some people's minds (e.g. mine).
Third, I think that we shouldn't hold up stabilization on this issue; we can resolve it in a subsequent PR or issue if you feel strongly.
Centril
commented
Jan 14, 2019
FCP has completed, and therefore: @bors r=SimonSapin p=1 |
bors
commented
Jan 14, 2019
📌 Commit e75dab7 has been approved by |
bors
commented
Jan 14, 2019
Stabilize core::convert::identity r? @SimonSapinfixes#53500 This is waiting for FCP to complete but in the interim it would be good to review.
bors
commented
Jan 14, 2019
☀️ Test successful - checks-travis, status-appveyor |
r? @SimonSapin
fixes#53500
This is waiting for FCP to complete but in the interim it would be good to review.