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"Useless syntax sugar": Numbered block parameters in Ruby (zverok.space)
submitted 2 years ago by to c/programming@programming.dev
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[–] 12 points 2 years ago (2 children)

It wouldn't be as relevant, since passing a function or method instead of a closure is much easier in Rust - you can just name it, while Ruby requires you to use the method method.

So instead of .map(|res| res.unwrap()) you can do .map(Result::unwrap) and it'll Just Work™.

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  • [–] 4 points 2 years ago (1 child)

    Except when Type::Method takes a reference, then it doesn't just work

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  • [–] -1 points 2 years ago* (last edited 2 years ago)

    Well, that's to be expected - the implementation of map expects a function that takes ownership of its inputs, so you get a type mismatch.

    If you really want to golf things, you can tack your own map_ref (and friends) onto the Iterator trait. It's not very useful - the output can't reference the input - but it's possible!

    I imagine you could possibly extend this to a combinator that returns a tuple of (Input, ref_map'd output) to get around that limitation, although I can't think of any cases where that would actually be useful.

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  • [–] 1 point 2 years ago* (last edited 2 years ago)

    In the case of your example we'd do .map(&:unwrap) in Ruby (if unwrap was a method we'd actually want to call)

    Notably, these are not the cases _1 and _2 etc are for. They are there for the cases that are not structurally "call this method on the single argument to the block" e.g. .map{ _1 + _2 } or .map { x.foo(_1) }

    (_1 is reasonable, because iterating over an enumerable sequence makes it obvious what it is; _1 and _2 combined is often reasonable, because e.g. if we iterate over a key, value enumerable, such as what you get from enumerating a Hash, it's obvious what you get; if you find yourself using _3 or above, you're turning to the dark side and should rethink your entire life)

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