Even with OverloadedRecordDot, Haskell’s records are still bad, they’re just not awful.

软件行业中，错误的做法往往得到更多的资源。下面是两个例子： 一个公司里面，技术债务最多的团队，员工最多。 问题最多的软件库或编程语言，产生最多的话题。

The IO monad wraps computations in the following context: "This computation can read information from or write information to the terminal, file system, operating system, and/or network". If you want to get user input, print a message to the user, read information from a file, or make a network call, you'll need to do so within the IO Monad. These are "side effects". We cannot perform them from "pure" Haskell code.

Haskell is the best functional programming language in the world and Neural Networks are functionsThis is the main motivation behind Hasktorch which lets you discover new kinds of Neural Network architectures by combining functional operators

Commonly the above definition is called the identity function. But in fact we should think of it as a whole family of functions. We should really say that id is an identity function for all types a. In other words, for every type T you might come up with, there is an identity function called id, which is of type T -> T. This is the type-checker’s view anyway, and by turning on the RankNTypes extension we can be explicit about that in our code: {-# LANGUAGE RankNTypes #-} id :: forall a. a -> a id x = x

Now it is much clearer that id is really a family of infinitely many functions. It is fair to say that it is an abstract function (as opposed to a concrete one), because its type abstracts over the type variable a. The common and proper mathematical wording is that the type is universally quantified (or often just quantified) over a.

It also adds safety through a property called parametricity. If we pretend that there are no infinite loops or exceptions (it’s okay to do that, so we will do it throughout this article), then the function is actually fully determined by its type. In other words, if we see the type a -> a, we know that the corresponding value must be the identity function.

In other words you cannot choose the definition of a value based on its type (for now).

function (or in the case of type classes, we call these methods)

If you can tell that two types are equal or not equal, that type belongs in the Eq type class.

Programming languages These will probably expose my ignorance pretty nicely.

Nix is a purely functional package manager. This means that it treats packages like values in purely functional programming languages such as Haskell — they are built by functions that don’t have side-effects, and they never change after they have been built.

This package takes a more declarative approach, and talks about events rather than signals. Widgets emit event values, and these values can be mapped and transformed into other values as the event propagates up the tree of widgets.

Haskell

-- FizzBuzz
module Main where

import Control.Monad

main :: IO ()
main = forM_ [1..100] $ \n -> putStrLn . concat . take 2 $
    ["Fizz" | n `mod` 3 == 0] ++ 
    ["Buzz" | n `mod` 5 == 0] ++ 
    ["", show n]

Deeper Stack Knowledge

(== 10)

Whereas normal type classes represent predicates on types (each type is either an instance of a type class or it isn’t), multi-parameter type classes represent relations on types

A History of Haskell:Being Lazy With Class

FRP library

foldMap :: Monoid m -> (a -> m) -> t a -> m

The notion behind it was that one could decompose, e.g., Applicative into an instance of the Pointed typeclass and an instance of the Apply typeclass (giving apply :: f (a -> b) -> f a -> f b) and an instance of Pointed, such that the two interact properly.