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Travis-Whitton's-MacBook-Pro:nix traviswhitton$ cat node.nix
# This imports the nix package collection,
# so we can access the `pkgs` and `stdenv` variables
with import <nixpkgs> {};

# Make a new "derivation" that represents our shell
stdenv.mkDerivation {
  name = "my-environment";

  # The packages in the `buildInputs` list will be added to the PATH in our shell

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#!/usr/bin/ruby
fh = File.new('names.csv', 'r')

names = []
while line = fh.gets
  line.chomp!
  names << line
end

names = names.shuffle

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Scalable program architectures
Haskell design patterns differ from mainstream design patterns in one important way:

Conventional architecture: Combine a several components together of type A to generate a "network" or "topology" of type B

Haskell architecture: Combine several components together of type A to generate a new component of the same type A, indistinguishable in character from its substituent parts

This distinction affects how the two architectural styles evolve as code bases grow.

The conventional architecture requires layering abstraction on top of abstraction:

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module Shape where

import Data.List (nub)

data Circle = Circle { radius :: Float }

data Triangle = Triangle { a :: Float, b :: Float, c :: Float }

class Dimensions shape where
  name :: shape -> String

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module Even where

import Prelude

import Data.Foldable (product)
import Data.Array (concatMap, null, sort, filter, length, (..))
import Data.Array.Partial (head, tail)
import Partial.Unsafe (unsafePartial)
import Control.MonadZero (guard)

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-- lazy vs non-lazy folds

-- works on infinite lists
take 5 $ foldr (:) [] [1..]

-- infinite loop
cons' = flip (:) -- acc is first arg to foldl
take 5 $ foldl cons' [] [1..]

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Optimization terminated successfully.
         Current function value: 0.375376
         Iterations: 6
         Function evaluations: 6339
                           Logit Regression Results                           
==============================================================================
Dep. Variable:                 agency   No. Observations:                31414
Model:                          Logit   Df Residuals:                    31315
Method:                           MLE   Df Model:                           98
Date:                Thu, 19 Apr 2018   Pseudo R-squ.:                  0.4584

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Optimization terminated successfully.
         Current function value: 0.272877
         Iterations: 8
         Function evaluations: 8498
                           Logit Regression Results                           
==============================================================================
Dep. Variable:                 agency   No. Observations:                31414
Model:                          Logit   Df Residuals:                    31313
Method:                           MLE   Df Model:                          100
Date:                Thu, 19 Apr 2018   Pseudo R-squ.:                  0.6063

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/usr/local/lib/python2.7/site-packages/statsmodels/compat/pandas.py:56: FutureWarning: The pandas.core.datetools module is deprecated and will be removed in a future version. Please use the pandas.tseries module instead.
  from pandas.core import datetools
/usr/local/lib/python2.7/site-packages/statsmodels/discrete/discrete_model.py:1214: RuntimeWarning: overflow encountered in exp
  return 1/(1+np.exp(-X))
/usr/local/lib/python2.7/site-packages/statsmodels/discrete/discrete_model.py:1264: RuntimeWarning: divide by zero encountered in log
  return np.sum(np.log(self.cdf(q*np.dot(X,params))))
Warning: Maximum number of iterations has been exceeded.
         Current function value: inf
         Iterations: 35
Traceback (most recent call last):

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module Main where

import Set
import Text.Pretty.Simple (pPrint)

c1  = Card { shape = Pill, color = Red, shade = Clear, count = One }
c2  = Card { shape = Squiggle, color = Purple, shade = Clear, count = Two }
c3  = Card { shape = Diamond, color = Green, shade = Clear, count = Three }
c4  = Card { shape = Squiggle, color = Purple, shade = Solid, count = Two }
c5  = Card { shape = Diamond, color = Green, shade = Solid, count = One }