exterm’s gists

exterm / phantom.hs

Created March 6, 2013 20:56

Example for Phantom Types in Haskell

	data PList a b = Nil
	\| Cons a (PList a b)

	test :: PList Int String
	test = Cons 3 $ Cons 2 $ Cons 1 Nil

	data Foo = Foo

	test2 :: PList Int Foo
	test2 = Cons 3 $ Cons 2 $ Cons 1 Nil

exterm / GADTs.hs

Created March 6, 2013 19:53

Example for Generalised Algebraic Datatypes in Haskell Used to create a safe list type

	data Safe a = Safe a
	data NotSafe = NotSafe
	data SafeList a b where
	Nil :: SafeList a NotSafe
	Cons :: a -> SafeList a b -> SafeList a (Safe b)


	safeHead :: SafeList a (Safe b) -> a
	safeHead (Cons x _) = x
	-- safeHead Nil = ???

exterm / 1_class.py

Created March 5, 2013 21:45

Translating Python to Haskell, keeping core concepts

	# A simple class in Python
	class car():
	# The __init__ method
	def __init__(self, color):
	self.color = color

	# The color method
	def color(self):
	return self.color

exterm / stringbool.rb

Created March 5, 2013 01:40

simple type problem in ruby

	irb(main):001:0> "false" ? true : false
	(irb):1: warning: string literal in condition
	=> true

	# no warning if string is not a literal

exterm / inference.hs

Last active December 14, 2015 03:59

Haskell underestimates parameter types and overestimates return types.

	and _ False = False
	and False _ = False
	and _ _ = True

	-- inferred type: Bool -> Bool -> Bool
	-- underestimated parameter type: the function would also work called like this:
	and 42 False
	-- and return False; the type checker throws an error for this though.

	and' _ False = 0

exterm / 1_types.hs

Last active December 13, 2015 21:38

Type System restrictions: Haskell forces constructors to be unambigous, erlang (dialyzer) doesn't care.

	data T1 = Bernd \| Uwe
	data T2 = Bernd \| Flo

exterm / Decoupling.hs

Last active December 10, 2015 19:39

Showing that a function that depends only on a single attribute of a map like data structure is also possible with static records/structs. This allows adding/removing attributes from the record without modification of the all_members function.

	data Project = Project {
	projId :: String,
	projKind :: ProjectKind,
	projDescription :: String,
	projBudget :: Int,
	projTeam :: [Person]
	}

	all_members :: [Project] -> [Person]
	all_members projects = concat $ map projTeam projects

exterm / mystery.rb

Created July 26, 2012 08:08

Clean Code.

	def nb_lines(width, text)
	text = "" if text.nil?
	cw = @CurrentFont['cw']
	width = @w - @rMargin - @x if (width == 0)
	wmax = (width - 2 * @cMargin) * 1000 / @FontSize
	s = text.gsub("\r", '')
	nb = s.length
	nb -= 1 if nb > 0 && s[nb-1] == "\n"
	sep = -1
	i, j, l = 0, 0, 0

exterm / gist:2160644

Created March 22, 2012 17:39

project layout

	.
	├── deps
	│ └── lager
	├── disco
	│ ├── ebin
	│ └── src
	├── launcher
	│ ├── ebin
	│ └── src
	├── main.config

exterm / rebar.config

Created March 22, 2012 17:29

rebar configuration

	% documentation for rebar.config: https://github.com/basho/rebar/blob/master/rebar.config.sample

	{sub_dirs, ["launcher", "disco"]}.

	{erl_opts, [debug_info, fail_on_warning, parse_transform, lager_transform]}.

	{require_otp_vsn, "R14"}.

	{deps,
	[lager,

Philip Theus (prev. Mueller) exterm