## Impossible Things ## @KevlinHenney “Sometimes I’ve believed as many as six impossible things before breakfast.”  ## Representations the Experts ## 97 Things Every Programmer Should Know O'REILLY® Edited by Kevlin Henney # Floating-Point Numbers Aren't Real Collective Wisdom from the Experts ## 97 Things Every Programmer

## +23 ## Things Happening in SG14 ## PATRICE ROY ## 20 23 October 01 - 06 ## Things happening in SG14 Making C++ better for game development & other low-latency domains Patrice Roy, CeFTI, Université Involved quite a bit with SG14, the low-latency study group Occasional WG21 secretary • etc. ## Things happening in SG14 • The abstract of this talk is as follows: • « The C++ committee is made of a larger number of study groups, including SG14 (low-latency, finances, games and embedded systems). ## Things happening in SG14 • The abstract of this talk is as follows: • « The C++ committee is made of a

# SOME THINGS C++ DOES RIGHT Patrice Roy Patrice.Roy@USherbrooke.ca; Patrice.Roy@clg.qc.ca CeFTI, Université de Sherbrooke; Collège Lionel-Groulx ## Who am I? • Father of five (four girls, one boy) Britannia with your favorite search engine • Used to write military flight simulator code, among other things • CAE Electronics Ltd, IREQ • Full-time teacher since 1998 • Collège Lionel-Groulx, Université heard • However, there are a significant number of things C++ does right ## You might have heard • However, there are a significant number of things C++ does right • There are a number of reasons why

uk/conferences/presentations.html ## Contents ## • Introduction • Qt —Setting Up Testing —Error-prone Things —Approval Tests • Extras -Tools —Summary ## About Me • Scientific C++ and Qt developer for testing ## Topics of this talk ## Contents • Introduction • Qt —Setting Up Testing —Error-prone Things —Approval Tests • Extras -Tools —Summary #### One framework. One codebase. Any platform testing your Qt application Effectively ## Contents • Introduction • Qt —Setting Up Testing —Error-prone Things —Approval Tests • Extras -Tools —Summary Q: How do I add tests to existing app? A: Ah

in other languages ## • Often the “escape clause” is C++ • So, C++ needs to be able to do unsafe things • Do so efficiently • While being safe where it matters • guaranteed • Preferably by default /1/b/9/c/1b9cd9b813d6969cbc81d03f0c93a897/p13_2.jpg) Being the world’s best at just one or two things isn’t enough  Essential for • type checking • overloading • adding user-defined types • consistent linking A few things are so important that you must introduce incompatibilities But you always pay dearly for that:

that can be comfortably read in a few hours. Certain topics won't be covered in order to keep things short. Specifically, the Handbook does not fully introduce core JavaScript basics like functions both of these values are callable, what do they return? The answers to these questions are usually things we keep in our heads when we write JavaScript, and we have to hope we got all the details right. string and number, we can identify their type at runtime using the typeof operator. But for other things like functions, there's no corresponding runtime mechanism to identify their types. For example

but typically bureaucratic and overly complex. • Dynamic languages can be easy to use, but are error-prone, inefficient, and break down at scale. • Concurrent programming is hard (threads, locks, headache) down”, “restart”, etc.). ## Go at Atlassian ## The Agent • A trivial Go program. • It does three things, forever: – Read VM state from /proc, – Encode the state information as a protocol buffer, – Broadcast interface for users and administrators. ## • command-line tools: — campout, put things in the blob store, — camget, get things from the blob store, – camsync, synchronize blob stores, – cammount, a FUSE

talk's contribution: Empirically catalog, classify, and count Common despair: “We can’t make things substantially better” This talk's contribution: A possible 30% reduction ... 1/3 of the way Artificial initial values are unuseful (overwritten), potentially expensive (dead writes), and error-prone (hide uninitialized use from UB tools). ## Alternative: Initialize before use ## I nitialize before talk's contribution: Empirically catalog, classify, and count Common despair: “We can’t make things substantially better” This talk's contribution: A possible 30% reduction ... 1/3 of the way

be "Code", initially), or via keyboard shortcuts. For more information on the different things you can do in a notebook, see the collection of examples. ## Code cells A code cell allows you input will be in the cell. This is convenient for doing quick experiments in place, or for querying things like filesystem content, without needing to create additional cells that you may not want to be saved • ContentsManager.pre_save_hook runs on the API path and model with content. This can be used for things like stripping output that people don’t like adding to VCS noise. • FileContentsManager.post_save_hook

codebase of hundreds of millions of lines are difficult to work with and hard to avoid if everyone puts things into the global namespace. Concede to optimization when necessary Performance optimizations can decide how to handle “can’t happen” failures in deeply nested functions, without the obscuring and error-prone bookkeeping of error codes. • Exceptions are used by most other modern languages. Using them in projects use exceptions, we need to advise against exceptions in Google open-source projects as well. Things would probably be different if we had to do it all over again from scratch. This prohibition also