Expression templates is a C++ template metaprogramming technique in which templates are used to represent part of an expression as a compile-time structure representing a flattened abstract syntax tree of said expression. It enables idioms like lazy evaluation and inter-procedurale optimization within the language itself.
Expression templates is a C++ template metaprogramming technique in which templates are used to represent part of an expression as a compile-time structure representing a flattened abstract syntax tree of said expression. It enables idioms like lazy evaluation and inter-procedural optimization within the language itself.
Seminal works on Expression Templates go back to Vandevoorde et al in their 2002 book 'C++ Templates: The Complete Guide' and Veldhuizen in the 1995 paper called 'Expression Templates'.
Classically, Expression Templates are used to capture arbitrary large expressions without any creation of temporaries. Said expression are usually transformed and turned into actual code within the proper evaluation context. Linear algebra libraries are the most frequent example of this technique but other domains like parser generator (Boost.spirit) or State Machine description (Boost.MSM) are known.
If many people still write Expression Templates by hand, Boost.proto provide a framework to develop them without all the required boilerplate. It also provides tree manipulation functions that simplify transformation of said expression.
Expression Template is often tied to Domain Specific Language as they provide an efficient way to implement hem inside C++.
