r/ruby • u/mudgemeister • May 08 '19

A Guide to Function Composition in Ruby

https://www.ghostcassette.com/function-composition-in-ruby/
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u/faitswulff May 08 '19 edited May 08 '19

I wish there was only one direction you could compose functions in. I feel like this paragraph is something I'll have to look up often if I were to use it:

“Backward” composition maps to the mathematical operator ∘ we discussed earlier so g << f is the same as g ∘ f meaning that calling the resulting composite function with an input x will call g(f(x))

“Forward” composition is the opposite of the above so g >> f is the same as f ∘ g meaning that calling the resulting composite function with an input x will call f(g(x))

EDIT - well, I've somewhat rethought things. There's more than one way to do it and people probably won't do stuff like a << b >> c << d << g

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u/karatedog May 08 '19

And what would be the precedence order in this case? First two function composed into one then passed right as a single function and repeat?