Capabilities appear to be the hot topic in the Scala community right now.
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As usual when looking at new features, I tend to ask myself the simple question of what problem is this trying to solve?And in this case, the most immediate answer I could find was to allow a direct style of programming.
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A direct style of programming is one in which control is passed implicitly from one line of code to the next, and is opposed to continuation passing style (or, equivalently, monadic style), where it's made explicit by a continuation.