chrisdone

Exploring possibilities with simple indexed fields

Database records and formlets and optionally populated records can be neatly all represented with the same data type when the fields are all indexed.

class Indexed i a where
  type Index i (a :: *)

chrisdone

Email message parsing in Haskell in 2018

Background: I am moving away from GMail to my own Haskell-based server (SMTP receiver/sender, web-based email client, spam filtering, etc.). All email to @chrisdone.com goes through this server (mx.chrisdone.com) as of today, and chrisdone@gmail.com forwards a copy of everything to it.

This is a summary/tracking document of my efforts to simply parse email messages in Haskell for the SMTP receiver.

chrisdone

(defun shoe-write-script (script)
  "Write SCRIPT to the proper place."
  (let* ((script-dir (shoe-script-dir script))
         (script-path (shoe-script-file-path "/" script-dir)))
    (with-temp-file script-path (insert script))))

(defun shoe-script-file-path (script &optional dir)
  "Produce the file path for SCRIPT."
  (concat (or dir (shoe-script-dir script))
          "/"

chrisdone

Statically checked overloaded strings

This gist demonstrates a trick I came up with which is defining IsString for Q (TExp a), where a is lift-able. This allows you to write $$("...") and have the string parsed at compile-time.

On GHC 9, you are able to write $$"..." instead.

This offers a light-weight way to enforce compile-time constraints. It's basically OverloadedStrings with static checks. The inferred return type

chrisdone

{-

Examples:

> reify @Int $ eval $ A (reflect (abs :: Int -> Int)) (I (-9))
9

> reify @Int $ eval $ A (A (reflect ((*) :: Int -> Int -> Int)) (reflect @Int 3)) (reflect @Int 5)
15

chrisdone

Installing a TLS SSL certificate in HAProxy from Namecheap - Sectigo Limited certificate

When buying an SSL certificate from Namecheap, you generate a CSR, which generates a private key, save that for later as private.key.

After you've paid for your certificate, you recieve a zip file that looks like this:

$ ls -alh
total 52K

chrisdone

FROM ubuntu:20.04

RUN apt-get update -y
RUN apt-get install -y python pip
COPY . /home/chris/Work/alphacephei/vosk-server
WORKDIR /home/chris/Work/alphacephei/vosk-server

RUN pip install -r requirements.txt && pip3 install sounddevice
RUN apt-get install -y libportaudio2

chrisdone

Introducing the stack hoogle feature!

With the release of hoogle5, we can now hoogle all local packages.

This let us implement stack hoogle, which is on the master branch of stack, but is not yet on a stack release. We'd like you to try it out before we do!

To upgrade to the latest stack from git, use:

chrisdone

-- This module demonstrates boxed vectors. That means they
-- contain values which are thunks, aka values of kind *, aka
-- values which may contain _|_. You can write any Haskell
-- value in here.
--
-- Optimizations:
--
-- 1) Use unsafeFreeze to avoid copying. See its haddocks.

-- 2) Use unsafeRead/unsafeWrite. These are, clearly, unsafe

chrisdone

import           System.Posix.Signals

main = do
   mainId <- RIO.myThreadId
  _ <-
    installHandler
      softwareTermination
      (CatchOnce
         (do S8.putStrLn "Received SIGTERM. Killing main thread."
             killThread mainId))