Cameron DaCamara cdacamar

Slightly Simplified Earley Parsing

Cody Miller

This is a quick note on Scott and Johnstone's "Recognition is not parsing - SPPF-style parsing from cubic recognisers" paper. It aims to explain one part of the Earley parser implementation of this algorithm and how it can be simplified by trading one problem for another. This is stitched together from my unpublished notes. Think of this less as a tutorial and more as a brain dump.

An interactive tool to parse and display the shared packed parse forests (SPPFs) described in the paper can be accessed here. The implementation there does not currently use the optimized implementation described here (and sketched in the original paper) nor the simplified form given below. It's probably useful to play around with that tool to get a feel for the structure of the SPPF nodes, as they aren't described much here.

I'm not going to do a big picture overview of t

Minimal D3D11

Minimal D3D11 reference implementation: An uncluttered Direct3D 11 setup + basic rendering primer and API familiarizer. Complete, runnable Windows application contained in a single function and laid out in a linear, step-by-step fashion that should be easy to follow from the code alone. ~200 LOC. No modern C++, OOP or (other) obscuring cruft. View on YouTube

Also check out Minimal D3D11 part 2, reconfigured for instanced rendering and with a smaller, tighter, simplified overall code structure, or Minimal D3D11 part 3, with shadowmapping + showcasing a range of alternative setup and rendering techniques.

What is the Strict Aliasing Rule and Why do we care?

(OR Type Punning, Undefined Behavior and Alignment, Oh My!)

What is strict aliasing? First we will describe what is aliasing and then we can learn what being strict about it means.

In C and C++ aliasing has to do with what expression types we are allowed to access stored values through. In both C and C++ the standard specifies which expression types are allowed to alias which types. The compiler and optimizer are allowed to assume we follow the aliasing rules strictly, hence the term strict aliasing rule. If we attempt to access a value using a type not allowed it is classified as undefined behavior(UB). Once we have undefined behavior all bets are off, the results of our program are no longer reliable.

Unfortunately with strict aliasing violations, we will often obtain the results we expect, leaving the possibility the a future version of a compiler with a new optimization will break code we th

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	// example how to set up D3D11 rendering on Windows in C

	#define COBJMACROS
	#define WIN32_LEAN_AND_MEAN
	#include <windows.h>
	#include <d3d11.h>
	#include <dxgi1_3.h>
	#include <d3dcompiler.h>
	#include <dxgidebug.h>

	#include <vector>
	#include <sstream>
	#include <iostream>
	#include <iterator>
	#include <tuple>

	template <typename T>
	std::vector<std::string> Split(T&& input) {
	std::stringstream ss{ std::forward<T>(input) };
	return std::vector<std::string> {std::istream_iterator<std::string>(ss), std::istream_iterator<std::string>{} };