1.9's New Methods
in [Ruby]
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From: Florian Gilcher on 15 Apr 2010 09:53 On Apr 15, 2010, at 1:06 PM, Intransition wrote: > First a big shout-out to Marc-Andre Lafortune and his <a href="http:// > github.com/marcandre/backports">backports</a> project. Nice work. > > Now I want to ask if others have noticed all the new methods being add > to 1.9+? I'm quite happy about vast majority of it, but there was at > least one method I thought pretty peculiar. This Enumerable method: > > def flat_map(&block) > return to_enum(:flat_map) unless block_given? > map(&block).flatten(1) > end unless method_defined? :flat_map > Backports.alias_method self, :collect_concat, :flat_map > > I am very curious to know how it was decided that a normal map > followed by a 1-deep flatten is common enough to warrant its own > method? Two in fact! > One advantage of :flat_map over map(...).flatten(...) is that it can be chained in an Enumerator. Sometimes, this can come in handy. Regards, Florian Gilcher
From: Ryan Davis on 15 Apr 2010 21:24 On Apr 15, 2010, at 06:34 , James Edward Gray II wrote: > On Apr 15, 2010, at 6:30 AM, Ryan Davis wrote: > >> i use Hash[*collection.map {...}.flatten] all the time. > > Me too, but it's needed less in 1.9 I think. Hash[ ] now accepts an Array of Arrays. nice. too bad I don't use 1.9 at all.
From: Jörg W Mittag on 17 Apr 2010 18:54
Intransition wrote: > First a big shout-out to Marc-Andre Lafortune and his <a href="http:// > github.com/marcandre/backports">backports</a> project. Nice work. > > Now I want to ask if others have noticed all the new methods being add > to 1.9+? I'm quite happy about vast majority of it, but there was at > least one method I thought pretty peculiar. This Enumerable method: > > def flat_map(&block) > return to_enum(:flat_map) unless block_given? > map(&block).flatten(1) > end unless method_defined? :flat_map > Backports.alias_method self, :collect_concat, :flat_map > > I am very curious to know how it was decided that a normal map > followed by a 1-deep flatten is common enough to warrant its own > method? Two in fact! #flat_map is monadic bind (also known as flatMap in Scala, SelectMany in .NET and (>>=) in Haskell). The other monadic operator that is needed to build a monad, is unit (aka return in Haskell), but in an OO language, that's just a factory method, IOW it's just .new in Ruby. So, #flat_map can potentially turn any class that mixes in Enumerable into a monad, provided that it also obeys the monad laws, of course. Whether or not that warrants its own method ... well, I have no idea. jwm |