FC++ is a library for doing functional programming in C++. The library provides a general framework to support various functional programming aspects, such as higher-order^[1] polymorphic^[2] functions, currying, lazy evaluation, and lambda. In addition to the framework, FC++ also provides a large library of useful functions and data types.

In FC++, we program with functoids, which are C++ classes or structs which overload operator() and obey certain other conventions. We will describe functoids in more detail in Section 5, Section 6, and Section 7. Functoids are simply our chosen representation for functions in C++; for now you may equate the terms "functoid" and "function" in your mind. Later we shall see what exactly a functoid is and why it is useful.

This document describes "Boost FC++". Prior to being "boostified", FC++ existed as a research project at Georgia Tech for a number of years [FC++]. This is the first document to describe the boostified version of FC++. It is important to note the changes made to the library between "FC++" and "Boost FC++", in order to understand the old documentation. The changes are mostly just a matter of naming conventions. In Table 1, we summarize the naming changes from FC++ to Boost FC++, by giving a sense of the general name changes as well as some particular examples. To avoid confusion, the reader of this document should at least be aware of this mapping before reading any of the prior documentation on FC++.

The only other major change to the library is that now the fun_type class only takes one argument (the result type). That is, code which used to say

   template <class X, class Y>
   struct sig : public fun_type<X,Y,Something> {};

now reads

   template <class X, class Y>
   struct sig : public fun_type<Something> {};

See Section 5 for details.