Herbert Wolverson - Rust Brain Teasers

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To Henry, my loyal canine coding companion of thirteen yearswho sadly didnt live to see the books release.

This book would not have been possible without the patience, support, and love of my wife, Mel Wolverson.

Margaret Eldridge deserves special thanks for suggesting that I write this book. I was midway through creating Hands-on Rust when she approached me with this title. After a brief moment of shell-shock that a publisher would come to me, I accepted. Thanks are also due to all of the staff at PragProgparticularly Dave Rankin and Miki Tebekafor letting me tweak the Brain Teasers genre a little for this title.

Thank you to Tammy Coronthe editorfor help and enthusiasm on this project. Tammy is an amazing editor, going above and beyond the call of duty by testing difficult code in the Rust Playground on top of keeping me focused and shepherding me through the publication process. I wouldnt have finished the book without her help.

My parentsRobert Wolverson and Dawn McLarendeserve a lot of gratitude. They sparked my love of computers at a young age, encouraging me to experiment and learn. They are both retired teachers and instilled in me a life-long love of learning and teaching.

Kent Froeschle and Stephen Turner, my colleagues at iZones , get a special thank you for their continual encouragement, work schedule flexibility, and patiently dealing with both a global pandemic and my writing schedule.

This book would not be what it is without the patient and thorough help of the tech reviewers: Jurgis Balciunas, Forest Anderson, Vladyslav Batyrenko, Bas Zalmstra, Remco Kuijper, Andy Lester, and countless beta-readers who submitted errata and questions. Thanks are also due to Steve Cotteril, for acting as a sounding-board throughout the creative process.

Rust is a very consistent language. The Rust Core Team has worked hard to ensure that Rust does what you ask and doesnt surprise you by performing additional tasks behind your back. Rusts toolsetparticularly Clippy and Rusts safety guaranteescheck your program for common mistakes and often suggest improvements. Its common for Rust programmers to notice that writing their program in Rust takes a little longer, but when they run it, it works as expected.

The Rust language has a few quirks. Sometimes they creep in at the cracks between systems, and sometimes theyre a conscious design choice to avoid doing something worse. In this book, youll review a series of self-contained Rust programs that explore these quirks. Each program, known as a brain teaser, teaches an aspect of Rust that is designed to surprise you. As you read each brain teaser, try to guess the programs output correctly. The possible answers are:

• The program wont compile.

• The program produces some unexpected output (for example, Arithmetic still works!).