InFact provides an interpreter and factory for the construction of instances of C++ classes. The syntax is very much like that of C++ itself, and objects may be created that wrap other objects, just like in C++. It supports all the common primitive types (bool, int, double, string), as well as vectors of primitives or of Factory-constructible objects. Here's what it looks like:

// Construct a cow with a required argument, its name.
Cow c1 = Cow(name("Bessie"));

// Construct a second cow with a different name, and an optional age.
// Also, specifying a type is optional, since InFact does type inference.
c2 = Cow(name("Lani Moo"), age(2));

// Construct a human pet owner with the two cows as pets.
PetOwner p = HumanPetOwner(pets({c1, c2}));

Feeding the above to InFact’s Interpreter class will construct three new objects at run-time (the referents of c1, c2 and p) without any new C++ code.

While being very powerful, the library is also quite lightweight: it is a simple recursive-descent parser with a single token of look-ahead, with the entire library implemented with fewer than 1000 C++ statements. The inspiration was the BeanShell library for Java, which provides a very convenient mechanism for configuration of any Java project. Similarly, InFact can be used as an effective configuration mechansim for C++ projects. See the ReFr project for an example, especially the default configuration file.

The interpreted InFact language supports type inference and named parameters. Compile-time equivalents of these two properties are available with the Boost Parameter library.

For documentation, please visit our documentation site.