frasertweedale

module Experiement where

import Data.Kind (Type)
import Data.Proxy (Proxy(..))

data VariantA
data VariantB
data VariantC

data Object (a :: Type) = Object

frasertweedale

Keybase proof

I hereby claim:

• I am frasertweedale on github.
• I am frasertweedale (https://keybase.io/frasertweedale) on keybase.
• I have a public key whose fingerprint is 5848 CE28 186B B469 C295 15E1 4B53 9052 4111 E1E2

To claim this, I am signing this object:

frasertweedale

module Main where

import Control.Monad (replicateM)
import Data.Char (ord)
import Data.Foldable (for_)
import Data.List (foldl')
import Data.Word (Word)
import System.Environment (getArgs)

hash :: [Char] -> Word

frasertweedale

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE MultiParamTypeClasses #-}

import Control.Applicative (Alternative(..))
import Data.Char (isDigit)

frasertweedale

module SubsetsMatchingCondition where

import Data.Maybe (mapMaybe)

data Cond a = Unsatisfied a | Satisfied a
  deriving (Show)

-- | Construct *minimal* subsets that satisfy the
-- condition upon the monoidal fold.  The monoidal
-- append must be "monotonic" for sensible results.

frasertweedale

Discussion topics

• Haskell base proposal (string types)
• Low/no-prep talks/seminars for meetups (see https://www.youtube.com/watch?v=uh24VwNhwY0&t=1875s)

Conferences

• YOW! Lambda Jam, May 5..6.
  • Tickets

frasertweedale

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.nio.charset.StandardCharsets;

import org.mozilla.jss.CryptoManager;
import org.mozilla.jss.InitializationValues;
import org.mozilla.jss.crypto.X509Certificate;

frasertweedale

import java.util.Hashtable;

import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.callback.Callback;

import netscape.ldap.LDAPConnection;
import netscape.ldap.LDAPEntry;
import netscape.ldap.LDAPUrl;

class Main {

frasertweedale

/* Composable errors via traits

A major challenge (among several) in error handling is how to deal with
disjoint error types produced by the libraries you use (as well as by
your own program) in a consistent and ergonomic way.  Rust's `?` operator
improves the ergonomics of error handling, but it can only be used with
a single error type throughout a single function.  Libraries define their
own error types and they don't know about each other, nor about the calling
program.  So if we want to deal with errors from different libraries as
a single type (an sum or enum of the different underlying error types), we

frasertweedale

{-# LANGUAGE KindSignatures #-}

module Workflow where

import Data.Bool (bool)


data Workflow a r
  = Decision a (Workflow a r) (Workflow a r)
  | Guard a (Workflow a r)