A technical notebook

Notes on functional (reactive) programming, recreational mathematics, and other etceteras — this is an attempt to learn in public, so, if there are typos or mistakes (there definitely will be), please reach out.

Here’s an RSS feed, for the nerds.

All entries

• A bug with Swift shorthand arguments
• Two implementations of delaySubscription
• Free variables in TCA dependencies
• withLatestFrom as a composed operator
• Iverson brackets and SwiftUI modifiers
• Party Parrot waves and Collection rotations
• Implementing AnyEquatable
• atan versus atan2
• Modifying the pairwise operator with a duplicated start
• AnyCancellable.store(in:) thread safety
• Mapping over the range and pattern matching operators
• Constant bindings as placeholders
• Publisher.zip completions
• Buffered and batched subscriptions in Combine
• little self, Big Self
• Simultaneously mapping over publisher values and errors
• Redirecting Publisher errors
• Mapping with parsers
• combineLatest’ing an empty collection
• From parsing operators to methods
• Empty reducers and the monoidal unit
• Conditional gestures in SwiftUI
• Swimming out past intuition
• Why folks use <> for same-type composition
• Pausing with Binding’s dynamic member subscript
• Stress testing variadic zip
• Why “sink?”
• Profunctors generalize relations
• All metric spaces are Lawvere metric spaces
• Easing AnyCancellable storage
• Weak assignment in Combine
• There’s sliced bread, and then Result.publisher
• Postfix type erasure
• Parity and arity
• Contrasting isomorphisms, equivalencies, and adjunctions
• Why optics?
• TIL about Publishers.MergeMany.init
• Naturality condition
• Why applicatives are monoidal
• Type erasure and forgetful functors
• Co-, contra-, and invariance
• What makes natural transformations, natural?
• “Oh, the morphisms you’ll see!”
• Getting an intuition around why we can call contramap a pullback
• (un)zurry
• ObservableType.do‌ or .subscribe (Publisher.handleEvents or .sink)?