Summary Curry’s paradox allows proofs of any statement in some languages that have the ability to construct a self referential sentence. This paradox allows a proof of any statement, no matter how absurd. Some statically typed programming languages allow for basic logical statements to be made and subsequently proven. …

Summary Switch statements over basic enums have lots of disadvantages. Many of the limitations can be overcome by using either dynamic dispatch, or the visitor pattern depending on your use case. In languages that support sum types natively, consider using those instead of the visitor pattern. Introduction I have seen several articles…

Summary “Don’t repeat yourself” (DRY) is a widely accepted programming principle, but it has several limitations An alternative derivation of DRY is presented, that aims to alleviate some of these limitations Programs are made up of functions, and to make functions maximally reusable they should: - Have the most lenient preconditions - Have…

Recently I made a game and entered it into the Github Game Off 2019. The premise of the game is that there are a series of cows that run around following rules. The aim in the earlier levels is to get all of the cows into a green area. …

Summary: A persistent data structure can easily keep track of previous versions of itself with little overhead. A regular data structure can be converted into a persistent one by replacing instances of Box with Rc, and replacing mutable dereferences with Rc::make_mut. The resulting structure is both more performant and uses less…

Summary Child entities which are both mutable and shared can make any, or all of their parents invalid. In freeform shared mutability, we cannot cache any calculation that depends on a shared mutable entity. If we limit the scope of sharing to code we trust not to invalidate our cache, then…

Summary For the majority of code, shared mutability is usually not required. We cannot have sharing, mutability and “internal consistency”. A program that tries to have all three is provably incorrect. If we want sharing, and mutability but do not need “internal consistency”, we can use a file, a database handle…

Summary Closures are a combination of a function pointer (fn) and a context. A closure with no context is just a function pointer. A closure which has an immutable context belongs to Fn. A closure which has a mutable context belongs to FnMut. A closure that owns its context belongs to…

Summary: Using “open” recursion: We can separate memoization logic from function logic. We can memoize functions without modifying the syntax of the function. We can make functions generic across multiple types of memoization. Memoization in Rust. Consider a recursive function. The most basic example is the Fibonacci sequence. Here is a naive implementation: …