serras

Program Analysis, a Big Happy Family

The idea behind program analysis is simple, right? You just want to know stuff about your program before it runs, usually because you don't want unexpected problems to arise (those are better in movies.) Then why looking at Wikipedia gives you headaches? Just so many approaches, tools, languages 🤯

In this article I would like to give a glimpse of an overarching approach to program analysis, based on ideas from abstract interpretation. My goal is not to pinpoint a specific technique, but rather show how they have common core concepts, the differences being due mostly to algorithmic challenges. In other words, static analysis have a shared goal, but it's a challenge to make them precise and performant.

Code is meant to be executed by a computer. Take the following very simple function:

fun cantulupe(x) = {

ChrisPenner

Optics By Example Cheat Sheets

The following are appendices from Optics By Example, a comprehensive guide to optics from beginner to advanced! If you like the content below, there's plenty more where that came from; pick up the book!

• Operators
• Composition Guide
• Substitution Guide
• Optical Constarints and Types

Operator Cheat Sheet

chrisdone

{-# LANGUAGE DataKinds #-}

-- | My database API.

module DBAPI where

import Data.Defaults

data ConnSpec p = ConnSpec
  { username :: !(Required p String)

jproyo

{-# LANGUAGE GeneralisedNewtypeDeriving #-}

module Data where

type UserName = String

data DataResult = DataResult String
  deriving (Eq, Show)

class Monad m => Cache m where

joshburgess

{-# LANGUAGE OverloadedLabels #-}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE DeriveGeneric #-}
module LensLabels where

import Prelude
import Control.Lens
import Data.Generics.Labels
import GHC.Generics

timvisee

Falsehoods programmers believe about time

This is a compiled list of falsehoods programmers tend to believe about working with time.

Don't re-invent a date time library yourself. If you think you understand everything about time, you're probably doing it wrong.

Falsehoods

• There are always 24 hours in a day.
• February is always 28 days long.
• Any 24-hour period will always begin and end in the same day (or week, or month).

jFransham

Achieving warp speed with Rust

Contents:

• Number one optimization tip: don't
• Never optimize blindly
• Don't bother optimizing one-time costs
• Improve your algorithms
• CPU architecture primer
• Keep as much as possible in cache
• Keep as much as possible in registers

mtesseract

The Problem

Defining records in Haskell causes accessor functions for the record's fields to be defined. There is no seperate namespace for these accessor functions.

The Goal

Be able to

• use records in Haskell, which share field names.
• use lenses for accessing these fields

ocharles

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

import Control.Monad.IO.Class
import Control.Monad.Trans.Class
import Prelude hiding (log)

--------------------------------------------------------------------------------
-- The API for cloud files.
class Monad m => MonadCloud m where
  saveFile :: Path -> Bytes -> m ()

CMCDragonkai

Foldl vs Foldr

I like to call foldr as "fold from the right", while foldl is "fold from the left".