tfausak

{-# language OverloadedStrings #-}
module Main ( main ) where
import qualified Control.Monad as Monad
import qualified Data.Aeson as Aeson
import qualified Data.Aeson.Encode.Pretty as Aeson
import qualified Data.Aeson.Types as Aeson
import qualified Data.Bifunctor as Bifunctor
import qualified Data.ByteString.Lazy as LazyByteString
import qualified Data.Csv as Csv
import qualified Data.HashMap.Strict as HashMap

tfausak

a = a :: Eq b => () -- AllowAmbiguousTypes
a = proc b -> id -< b -- Arrows
a = let !b = () in b -- BangPatterns
a = 0b0 -- BinaryLiterals
a = id do 0 -- BlockArguments
foreign import capi "" a :: ()
class A b where c :: Eq b => b -- ConstrainedClassMethods
type A = Eq -- ConstraintKinds
# -- CPP
import Data.Proxy; a = Proxy :: Proxy True -- DataKinds

tfausak

{-
this is a little experiment to parse a module with ghc
and extract exports identifiers, top-level declarations, and (documentation) comments
the idea is to use this as a basis for a haddock-like tool
that doesn't require type checking a module in order to run
-}
module Main ( main ) where

import qualified Control.Monad
import qualified DynFlags

tfausak

/.stack-work/
/output/
/results.csv
/stack.yaml.lock

tfausak

-- I am working on a tool that downloads the Hackage index, stores it, and
-- processes it. I am storing the index in PostgreSQL. I want to keep the
-- maximum residency down. I don't care too much about total runtime.
--
-- This file contains a bunch of different operations in various formats. The
-- idea is to get a baseline measurement for each operation (like downloading
-- the index or reading it from a file) and each format (streaming, lazy, or
-- strict). Those measurements can be used to create a minimum memory
-- requirement for the actual tool.
--

tfausak

Invertible syntax descriptions

An "invertible syntax description" is something that can be used to both parse and generate a syntax. For example, instead of defining separate toJson and fromJson functions for a given data type, an invertible syntax description could be used to provide both. There are many Haskell libraries that provide this functionality or something close to it. As far as I can tell most of them are at least inspired by Invertible syntax descriptions by Tillmann Rendel and Klaus Ostermann.

Personally I am interested in using these for HTTP routing. I frequently want to be able to define a route such as /episodes/:id.json, dispatch based on that route, and generate links to that route. Doing so manually is tedious and error prone.

tfausak

-- Like Ratio but not broken.
module Quotient
  ( Quotient
  , quotient
  , unsafeQuotient
  , (%)
  , numerator
  , denominator
  , fromRatio
  , toRatio

tfausak

  60,974,182,000 bytes allocated in the heap
 263,226,596,160 bytes copied during GC
     652,502,280 bytes maximum residency (815 sample(s))
       3,177,208 bytes maximum slop
             622 MB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0     57804 colls,     0 par    2.359s   2.372s     0.0000s    0.0006s
  Gen  1       815 colls,     0 par   245.031s  246.321s     0.3022s    0.6341s

tfausak

#!/usr/bin/env stack
-- stack --resolver lts-13.0 script
{-# OPTIONS_GHC -Weverything -Wno-implicit-prelude -Wno-unsafe #-}

module Main ( main ) where

import qualified Data.Aeson
import qualified Data.Aeson.Types
import qualified Data.List
import qualified Data.Ord

tfausak

-- This whole thing is shamelessly stolen from:
-- <https://doisinkidney.com/snippets/nary-uncurry.html>.

-- Without flexible instances, GHC complains about the `HasApply` instances:
--
-- > Illegal instance declaration for `HasApply a Z`. All instance types must
-- > be of the form `(T a1 ... an)` where `a1 ... an` are *distinct type
-- > variables*, and each type variable appears at most once in the instance
-- > head.
--