Clojerks Swarm: Coin Kata

Clojerks is Portland's Clojure User Group.

This is the result of the group swarm coding on the Coin Kata

Write a program that will correctly determine the least number of coins to be given to the user such that
the sum of the coins' value would equal the correct amount of change.

Input: change amount 
Input: coin denomination array (ie [1, 5, 10, 25, 100] ) => [we'll use a sorted-set]
Output: number of coins array (ie [1, 0, 1, 0, 0] would represent $0.11 => [we'll use a hashmap {1 1, 5 0, 10 1, 25 0, 100 0}]

For example
An input of 15 with [1, 5, 10, 25, 100] should return fifteen cents or [0, 1, 1, 0, 0]
An input of 40 with [1, 5, 10, 25, 100] should return two dimes or [0, 1, 1, 1, 0]

Ideas to expand on

• Type the solution with typed-clojure
• Solve the problem with core.logic and the new support for constraints
• Optimize the program with reducers
• Expose the solution as a RESTful web service
• Port the solution to ClojureScript, compile it, and deploy it
• Use test.generative to test the program
• Make it into a Leiningen plugin

A General Overview

Using the Clojure REPL

More to come, but: lein repl

Working with Clojure

Emacs tips

The best Clojure setup for Emacs is "Emacs-live" - but basic clojure-mode+swank+nrepl support is also possible

• https://github.com/kingtim/nrepl.el
• https://github.com/overtone/emacs-live
• https://github.com/technomancy/swank-clojure [deprecated for nREPL]

Emacs Live provides great documentation for getting started. It covers Clojure, Paredit, and live editing:

• http://overtone.github.com/emacs-live/documentation.html

Vim tips

In vim, I suggest you use pathogen.vim and install Foreplay and VimClojure-static

Here are helpful Foreplay commands

• K - lookup word
• gd - goto definition (ctrl-w g d is most helpful)
• gf - goto file (ctrl-w g f is most helpful)
• [d - source lookup of word
• cpp - eval paragraph
• cpr - require file (if aliased)
• cpw - eval word (see what it's bound/def'd to)
• :Source, :Doc, :FindDoc, and :Apropros
• :make - is connected to lein, so :make test works

Paredit.vim tips

I also make use of paredit.vim. This assumes your <leader> is \

• :call PareditToggle() - toggle it on and off.
• \W wrap in paren (works with visual selection too)
• \J join paren - (a)(b) -> (a b)
• \O split paren - (a b) -> (a)(b)
• \S splice paren - ((a b)) -> (a b)
• \< move left - moves parens around blocks (a)|(b) -> ((a) b)
• \> move right - moves parens around blocks (a|)(b) -> (a (b))
• [[ and ]] browses across top-level forms
• ( and ) browses across parens

Wrapping can also be tailored, and used on a visual block:

• \w"
• \w[
• \w(

Other useful tips

Other VIM tips

• Use surround.vim

License

Copyright © 2012 Paul deGrandis // Clojerks

Distributed under the Eclipse Public License, the same as Clojure. Please see the LICENSE_epl.html for details.