DRY

on't

epeat

ourself

GoUp(1)
Rotate(120)
GoUp(1)
Rotate(120)
GoUp(1)
Rotate(120)

GoUp(1)
Rotate(90)
GoUp(1)
Rotate(90)
GoUp(1)
Rotate(90)
GoUp(1)
Rotate(90)

We Enjoy Typing

WET code

DRYing the code

polygon(n) {
    for (int i = 0 ; i < n ; i++) {
        GoUp(1)
        Rotate(360/n)
    }
}

DRYing

with loops

polygon(n) = replicateM n (do 
                        GoUp(1) 
                        Rotate(360/n)
            )

DRYing with higher order functions

Knowledge: Polygon(n) = a set of lines
Problem:
- Get the set of lines for a certain N
- Check if there exist an N such that the Polygon(N) is my set of lines

As long as you're not reading the fine print, it is.

{
	∀ x y: Reachable(x,y) ↤ Edge(x,y).
	∀ x y: Reachable(x,y) ↤ ∃ z: Reachable(x,z) 
                                    & Reachable(z,y).
}

in 80%* of the theories

*non-scientific number

C-style macros

When creating a language, enable the programmer to program DRY!

My question for you:

≟