johnchandlerburnham

A Taxonomy of Self-Types

Part I: Introduction to Self-Types

Datatypes in the Formality programming language are built out of an unusual structure: the self-type. Roughly speaking, a self-type is a type that can depend or be a proposition on it's own value. For instance, the consider the 2 constructor datatype Bool:

chrisdone

{-# LANGUAGE DataKinds #-}

-- | My database API.

module DBAPI where

import Data.Defaults

data ConnSpec p = ConnSpec
  { username :: !(Required p String)

TOTBWF

-- |
  -- Module      :  Lift
  -- Copyright   :  (c) Reed Mullanix 2019
  -- License     :  BSD-style
  -- Maintainer  :  reedmullanix@gmail.com
  --
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}

andymatuschak

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

jibsen

Code

Here are two simple CMake functions that take a list of compiler flags, and append those that do not result in an error when used to the supplied variable.

Depending on which version of CMake you need to support, you might want to look into the COMPILE_FLAGS property and target_compile_options().

mikehearn

interface SerializeableWithKryo

class ImmutableClassSerializer<T : SerializeableWithKryo>(val klass: KClass<T>) : Serializer<T>() {
    val props = klass.memberProperties.sortedBy { it.name }
    val propsByName = props.toMapBy { it.name }
    val constructor = klass.primaryConstructor!!

    init {
        // Verify that this class is immutable (all properties are final)
        assert(props.none { it is KMutableProperty<*> })