Value Oriented Programming

Prior Lecture: A Possible Future of Software Development

  • Sean Parent (2007 BoostCon)

Prior Lecture: Am I a good progammer?

  • Kate Gregory

Prior Lecture: Simple Made Easy

  • Rick Hickey (Clojure)

Prior Reading: Grokking Simplicity

  • Eric Normand

Prior Reading: THE USE OF SUB-ROUTINES IN PROGRAMMES

  • David John Wheeler

Functions

You say you want to write a function…

  • You don't want to write a function

We just want to change the code

  • add a feature
  • fix a bug

example code 

#+src_begin

void firstCitizenFunction() { Projector proj … proj.showPattern(delta)

// if facing North (0) double tolerance = 5.0 if (proj.seria;Number() < 12345678) tolerance *= 2; Orientation dir = proj->getPose().orientation(); if (dir.yaw() < tolerance * MPI / 180

dir.yaw() > (360 * tolerance) * MPI / 180)

… }; 

#+src_end
#+src_begin

void firstCitizenFunction() { Projector proj …

if (isFacingNorth(proj)) … };

bool isFacingNorth(Projector proj) { auto dir = proj.orientation(); auto tolerance = proj…

proj.getMODEL()->getThing()->etc…

… math on dir … if (… < tolerance …) return true; return false; } 

#+src_end

Barrier to Complecting

`bool isFacingNorth(Orientation dir, double tolerance)`

Code top-down on the way down

  • And bottom-up on the way back up

Keep Your Stuff Separate (KYSS)

Place-Oriented Programming (PLOP)

  • values you dont care about the address or identity

  • Testability + Safety

Complecting

Simple/Complex - plecto (latin) = fold/braid

  • simple = one fold
  • complex = many folds

Easy - adjacens (latin) = close at hand

  • complecting = interweaving

C++ Koan

"Theres a functions for that" "Whats it called" "Guess" "<insertNestedIdiomaticFunctionName>" "It didn't compile" "Well write the function you want to see in the world"

"Master, I am honoured" "I was walking my dog, your function grasshopper" "Why does it take a BasaeCommonStruct instead of just x and y?" "BCS is where we keep x and y master" <Bark> "He's Hungry" "Shall I prepare him food master?" "No just open the fridge, let him take what he wants"

Separate calculating from doing

  • Takes input, MODIFIES it, produces output

"returing void is a code smell"

"pure functions"

  • same input gives same output
    • no side effects

void StarOn(Sneetch & sneetch, int num) { vector locs = calcStarPos(sneetch, num); applyStars(sneetch, locs); };

"local reasoning"

  • changing the physical universe versus the digital interconnected processes

Sub-routines

  • self-contained part of a programme
    • an entity of its own
  • allows the coder to concentrate on one section of a programme at a time without the overall detailed programme continually intruding

"functions are the fundamental building block of programming"

class Device { virtual bool isFacingNorth() const; }

class MediaServer : Device { … }

class Projector: Device { bool isFacingNorth() const override; }

class DirectionalDevice: Device { … }

class Projector : DirectionalDevice { … }

"good way of sharing functions? writing functions!"

  • functions are for sharing

Uses external Orientation API `bool isFacingNorth(Orientation, double);` v.s. Access internals ``` class Orientation { … bool isFacingNorth(double tol) const; … }; ````

  • everytime you add a new function to your class
    • its gets heavier and denser "classes are made of Velcro"

"Classes are a nexus of Complecting"

Good Code - begets good code - works (while bad code does not work)

Invariants in classes are properties that will always hold true for all objects of a class

  • ensures state remains valid and maitained by class methods

"No raw loops" - Sean Parent

Map of Vectors or Multi-Map