Jon Purdy evincarofautumn

Factoring and Generalizing in Haskell

Suppose we want to write a simple function f to calculate the sum of the squares of the even numbers in a list. We can start by writing down some examples of expected inputs and outputs.

f [] == 0
f [2] == 4
f [3] == 0
f [4] == 16
f [2, 4] == 20

Grammar of Kitten

This is an annotated EBNF grammar of the latest rewrite of Kitten. Items marked with a dagger (†) are explained in the surrounding prose, not in EBNF.

Source Locations

The source column of a token is the offset to its first character within the line in which it appears. The indentation of a line is the source column of the first token in the line. Tab characters are illegal.

Layout

Thoughts on an InlineDoBind extension

An expression beginning with a left arrow (<-) inside a do block statement is desugared to a monadic binding. This is syntactically a superset of existing Haskell, including extensions. It admits a clean notation that subsumes existing patterns and comes with few downsides.

Examples

do
  f (<- x) (<- y)
-- ===

	class (Monad m) => PureMonad m where
	run :: m a -> a

	instance PureMonad Maybe where
	run = fromJust

	instance PureMonad (Either a) where
	run = fromRight

	instance PureMonad [] where

	import Control.Monad.Trans.Cont
	import GHC.Exts (IsString(..))

	instance (Num a) => Num (ContT r m a) where

	fromInteger x = ContT (\k -> k (fromInteger x))
	{-
	fromInteger = ContT . flip ($) . fromInteger
	-}

	# cmake CMAKE_TOOLCHAIN_FILE=".../linux-i686.toolchain.cmake" .../rr

	set(CMAKE_SYSTEM_NAME Linux)
	set(CMAKE_SYSTEM_ARCHITECTURE i686)

	set(CMAKE_C_COMPILER gcc -m32)
	set(CMAKE_CXX_COMPILER g++ -m32)

	#include <iostream>
	using namespace std;

	#define CHECK_ASSUMPTIONS 0

	#if CHECK_ASSUMPTIONS
	#define ASSUMING(...) __VA_ARGS__
	#else
	#define ASSUMING(...)
	#endif

	#!/usr/bin/env perl

	# Usage: ./most-included.pl $(find mono -name '*.h')

	use warnings;
	use strict;

	my %forward = ();

	while (<>) {

	Building: Shared (Debug)

	Building: XamarinAndroid (Debug)

	Build started 2/24/2015 1:06:44 PM.
	__________________________________________________
	Project "/Users/jonathanpurdy/Projects/Mobile-App-Performance/Xamarin/XamarinAndroid/XamarinAndroid.csproj" (Build target(s)):

	Initial Properties:
	__CF_USER_TEXT_ENCODING = 0x1F5:0:0

	Git submodules updated successfully
	/Applications/Xcode.app/Contents/Developer/usr/bin/make all-recursive
	Making all in po
	Making all in mcs
	make[3]: Nothing to be done for `all-am'.
	Making all in libgc
	Making all in m4
	make[3]: Nothing to be done for `all'.
	Making all in include
	Making all in private