Andrei Alexandrescu

Tudor Andrei Cristian Alexandrescu (born 1969) is a Romanian-American C++ and D language programmer and author. He is particularly known for his pioneering work on policy-based design implemented via template metaprogramming. These ideas are articulated in his book Modern C++ Design and were first implemented in his programming library, Loki. He also implemented the "move constructors" concept in his MOJO library. He contributed to the C/C++ Users Journal under the byline "Generic  ".

He became an American citizen in August 2014.

Education and career
Alexandrescu received a B.S. degree in Electrical Engineering from Polytechnic University of Bucharest (Universitatea Politehnica din București) in July 1994.

His first article was published in the C/C++ Users Journal in September 1998. He was a program manager for Netzip, Inc. from April 1999 until February 2000. When the company was acquired by RealNetworks, Inc., he served there as a development manager from February 2000 through September 2001.

Alexandrescu earned a M.S. (2003) and a PhD (2009) in computer science from the University of Washington.

In 2006 Alexandrescu began assisting Walter Bright on the development of the D programming language. He released a book titled The D Programming Language in May 2010.

From 2010 to 2014, Alexandrescu, Herb Sutter, and Scott Meyers ran a small annual technical conference called C++ and Beyond.

Alexandrescu worked as a research scientist at Facebook for over 5 years, before departing the company in August 2015 in order to focus on developing the D programming language.

In January 2022, Alexandrescu began working at Nvidia as a Principal Research Scientist.

Expected
Expected is a template class for C++ which is on the C++ Standards track. Alexandrescu proposes  as a class for use as a return value which contains either a T or the exception preventing its creation, which is an improvement over use of either return codes or exceptions exclusively. Expected can be thought of as a restriction of sum (union) types or algebraic datatypes in various languages, e.g., Hope, or the more recent Haskell and Gallina; or of the error handling mechanism of Google's Go, or the Result type in Rust.

He explains the benefits of  as:
 * Associates errors with computational goals
 * Naturally allows multiple exceptions in flight
 * Switch between "error handling" and "exception throwing" styles
 * Teleportation possible across thread boundaries, across nothrow subsystem boundaries and across time (save now, throw later)
 * Collect, group, combine exceptions

Example
For example, instead of any of the following common function prototypes:

or

he proposes the following:

Scope guard
From 2000 onwards, Alexandrescu has advocated and popularized the scope guard idiom. He has introduced it as a language construct in D. It has been implemented by others in many other languages.