Paul Young paulyoung

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

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

Use Proxy for Git/GitHub

Generally, the Git proxy configuration depends on the Git Server Protocol you use. And there're two common protocols: SSH and HTTP/HTTPS. Both require a proxy setup already. In the following, I assume a SOCKS5 proxy set up on localhost:1080. But it can also be a HTTP proxy. I'll talk about how to set up a SOCKS5 proxy later.

SSH Protocol

When you do git clone ssh://[user@]server/project.git or git clone [user@]server:project.git, you're using the SSH protocol. You need to configurate your SSH client to use a proxy. Add the following to your SSH config file, say ~/.ssh/config:

ProxyCommand nc -x localhost:1080 %h %p

	-- in response to https://twitter.com/chrislpenner/status/1221784005156036608
	--
	-- The goal is to mimic this Scala code, but in Haskell:
	--
	-- > "spotify:user:123:playlist:456" match {
	-- > case s"spotify:user:$userId:playlist:$playlistId"
	-- > => ($userId, $playlistId) // ("123", "456")
	-- > }
	{-# LANGUAGE DeriveFunctor, LambdaCase, PatternSynonyms, QuasiQuotes, RankNTypes, TemplateHaskell, TypeOperators, ViewPatterns #-}
	{-# OPTIONS -Wno-name-shadowing #-}

	use std::str;

	fn main() {
	// -- FROM: vec of chars --
	let src1: Vec<char> = vec!['j','{','"','i','m','m','y','"','}'];
	// to String
	let string1: String = src1.iter().collect::<String>();
	// to str
	let str1: &str = &src1.iter().collect::<String>();
	// to vec of byte

	const getSvgNamesForNodes = () => {
	// this is guesswork. When Figma has two nodes with the same name (say, "Union"),
	// it serialises them into SVG with names "Union" and "Union_2", but it's not
	// clear which one becomes "Union" and which "Union_2". It is theorised that this
	// is done in the same order that .findAll returns, so we make use of that.
	// Figma might decide to change this at any time, of course. It would be much
	// nicer if there were an SVG export option which also serialised getPluginData()
	// data as data-* attributes in the output SVG, but there isn't, yet.
	let names = {};
	let nameIndices = {};

	import * as vscode from "vscode";
	import { initUsePackage, usePackage, configSet } from "vscode-use-package";

	import * as nav from "./nav";
	import * as js from "./js";
	import * as rust from "./rust";

	export function init(context: vscode.ExtensionContext) {
	console.log(`HELLO FROM INIT SCRIPT`);

	{-# language TypeInType #-}

	-- \| Types which have PureScript equivalents
	class ToPursTyCon a where
	toPursTyCon :: Tagged a PursTypeConstructor

	-- \| The default instance uses 'G.Generic' and pattern matches on the
	-- type's representation to create a PureScript type.
	default toPursTyCon :: (G.Generic a, GenericToPursTyCon (G.Rep a)) => Tagged a PursTypeConstructor
	toPursTyCon = retag $ genericToPursTyConWith @(G.Rep a) defaultPursTypeOptions

	let UserContext = React.createContext();

	class App extends React.Component {
	state = {
	user: null,
	setUser: user => {
	this.setState({ user });
	}
	};

	SSE3=1 SSSE3=1 SSE4_1=1 SAHF=1 AVX=1 FMA3=1 BMI1=1 BMI2=1 LZCNT=1 POPCNT=1 ATOM=0
	Synopsis:
	shell [options] [--shell] [<file>...]
	d8 [options] [-e <string>] [--shell] [[--module] <file>...]

	-e execute a string in V8
	--shell run an interactive JavaScript shell
	--module execute a file as a JavaScript module

	Options: