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10770 :: Why is `enumerate()` a macro?

[2023-12-15T18:08:20+01:00]

goldsteinq (orginal) [2023-12-15T18:08:20+01:00] view original

Hi! I’ve noticed that enumerate() is a macro that transforms a for loop. It seems like it would be easy to make it an iterator instead. Iterators are easier to implement and more composable (e.g. could be passed to templates). PR that originally added them seems to suggest that it’s because it was added before concepts, would it make sense to make enumerate() an iterator now?

Calonger (orginal) [2023-12-15T18:34:28+01:00] view original

Iterator is only composible in iterator () : T form . Using means runtime closure , expensive .

Araq (orginal) [2023-12-15T19:55:13+01:00] view original

Iterators are easier to implement and more composable (e.g. could be passed to templates).
The macro has already been implemented and guarantees no overhead.

awr1 (orginal) [2023-12-15T21:02:03+01:00] view original

what even is the difference in functionality between enumerate and the pairs iterator?

choltreppe (orginal) [2023-12-15T21:46:53+01:00] view original

enumerate always just counts the iterations starting from 0. pairs goes through the indecies of the array (which can be any ordinal or subrange of one). or for tables it goes through the keys.