philipschwarz

flatten is indeed an interesting topic - one cool thing is that flatMap is just map followed by flatten, i.e. (ma flatMap f) == (ma map f flatten) [1].

Another is that flatten is flatMap(identity) [2][3].

Another is that a monad can be defined as a functor with a unit function (i.e. a type constructor like List or Option) and a flatten function (aka join in Haskell) [4]

[1] https://github.com/philipschwarz/scala-fp-combinators-code-kata/blob/master/src/main/scala/FPCombinatorsCodeKata.scala#L18 - https://www.slideshare.net/pjschwarz/scala-functional-programming-combinators-code-kata
[2] https://github.com/philipschwarz/scala-fp-combinators-code-kata/blob/master/src/main/scala/FPCombinatorsCodeKata.scala#L20 
[3] https://www.slideshare.net/pjschwarz/symmetry-in-the-interrelation-of-flatmapfoldmaptraverse-and-flattenfoldsequence
[4] https://www.slideshare.net/pjschwarz/monad-as-functor-with-pair-of-natural-transformations#8

philipschwarz

# This file was automatically generated by 'stack init'
#
# Some commonly used options have been documented as comments in this file.
# For advanced use and comprehensive documentation of the format, please see:
# https://docs.haskellstack.org/en/stable/yaml_configuration/

# Resolver to choose a 'specific' stackage snapshot or a compiler version.
# A snapshot resolver dictates the compiler version and the set of packages
# to be used for project dependencies. For example:
#

philipschwarz

name:                sierpinski
version:             0.1.0.0
github:              "githubuser/sierpinski"
license:             BSD3
author:              "Author name here"
maintainer:          "[email protected]"
copyright:           "2021 Author name here"

extra-source-files:
- README.md

philipschwarz

module Main where

import Lib

{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS -Wall -fno-warn-type-defaults #-}
import Graphics.Gloss   
import Data.Monoid
 
window :: Display

philipschwarz

import cats.effect._
import cats.effect.unsafe.implicits.global
import fs2._

import java.time.Instant
import scala.concurrent.duration._

object Mine extends App {

  val s =

philipschwarz

import anticipation.Text
import gossamer.t
import quantitative.{Kilograms, Metres, Quantity}
import turbulence.Out

type Bmi = Quantity[Kilograms[1] & Metres[-2]]

case class Person(
  name: Text, 
  age: Int, 

philipschwarz

ThisBuild / version := "0.1.0-SNAPSHOT"

ThisBuild / scalaVersion := "3.5.0"

lazy val root = (project in file("."))
  .settings(
    name := "try-contingency"
  )

libraryDependencies += "dev.soundness" % "quantitative-core" % "0.1.0"

philipschwarz

scala: ## Exception when compiling 1 sources to /Users/philipschwarz/dev/git/try-contingency/target/scala-3.5.0/classes
java.lang.AssertionError: assertion failed: class inequality has non-class parent: AppliedType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object hypotenuse),Inequality),List(AppliedType(TypeRef(ThisType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object quantitative),module class Quantitative$)),type Quantity),List(TypeRef(ThisType(TypeRef(ThisType(TypeRef(ThisType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object quantitative),module class Quantitative$)),module class Quantity$)),class inequality)),type UnitsType))), AppliedType(TypeRef(ThisType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object quantitative),module class Quantitative$)),type Quantity),List(TypeRef(ThisType(TypeRef(ThisType(TypeRef(ThisType(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object quantitative),module class Quanti