virtualsafety virtualsafety

Concept-based polymorphism in modern C++


Date	05-05-2021 - 10-17-2023
Revision	R3
Author	Guillaume Dua
Reviewers	Loïc Joly, Antoine Morrier

C++ : Polymorphic inheritance without vtable

Inheritance and Virtual Table are often used to create interface in C++ polymorphic class
What if ... there were another way to do this ?
easier, cleaner, faster and more reliable
This article explains how to use CRTP, [std::variant](https://en.cppreference.com/w/cpp/utility/variant and std::visit to increase code performance.

Table of content

Introduction

A short demo showing the explicit instantiation of templates, and how to avoid parsing the full definition(s) in every compilation unit. The limitation is that it will only be possible to use the specific specialisations explicitly instantiated in the cpp file.

Applied Functional Programming with Scala - Notes

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

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	#include <bits/stdc++.h>
	using namespace std;

	struct node {
	int data{};
	node* left = nullptr;
	node* right = nullptr;
	node* parent = nullptr;
	string color;
	};

	#pragma once

	#include <type_traits>
	#include <limits>

	// The default enumeration category. Conversion is equivalent to static_cast.
	// Unspecialized enumeration traits use this category.
	struct enum_default { };

	// The standard-layout enumeration category. Values outside the given range are

	SELECT
	*,
	pg_size_pretty(table_bytes) AS table,
	pg_size_pretty(index_bytes) AS index,
	pg_size_pretty(total_bytes) AS total
	FROM (
	SELECT
	*, total_bytes - index_bytes - COALESCE(toast_bytes, 0) AS table_bytes
	FROM (
	SELECT

	/***
	* Excerpted from "The Definitive ANTLR 4 Reference",
	* published by The Pragmatic Bookshelf.
	* Copyrights apply to this code. It may not be used to create training material,
	* courses, books, articles, and the like. Contact us if you are in doubt.
	* We make no guarantees that this code is fit for any purpose.
	* Visit http://www.pragmaticprogrammer.com/titles/tpantlr2 for more book information.
	***/
	import org.antlr.v4.runtime.*;
	import org.antlr.v4.runtime.tree.ParseTree;

	-- Create a group
	CREATE ROLE readaccess;

	-- Grant access to existing tables
	GRANT USAGE ON SCHEMA public TO readaccess;
	GRANT SELECT ON ALL TABLES IN SCHEMA public TO readaccess;

	-- Grant access to future tables
	ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readaccess;