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Focused transactional state updates: (%%=) :: Has (State s) sig m => Lens' s a -> StateC a m () -> m () lens %%= action = use lens >>= (`execState` action) >>= (lens .=) e.g.: _player %%= handleControls

Rob Rix‎

@rob_rix

Jan 1, 2020

1. handleControls only gets access to the player, not the rest of the state it’s drawn from. separation of concerns! 2. errors thrown in handleControls won’t result in incomplete state updates—the player is only updated if handleControls finishes successfully.

Rob Rix‎

@rob_rix

Jan 1, 2020

Programmable control flow is amazing.

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Rob Rix‎

@rob_rix

Jan 1, 2020

That sounds excruciating 😬

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Rob Rix‎

@rob_rix

Jan 1, 2020

Frank is super cool 💙

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Rob Rix‎

@rob_rix

Jan 1, 2020

that is exciting to hear!

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Replying to

and

Was actually looking back at some of the Epigram stuff again recently - ie. "The View from the Left" and some of the old languages guides, and having a peek at the source code and examples of version 1 & 2. Would really be interested to know more about what you learned from it!

10:07 PM · Jan 1, 2020Twitter Web App