FunctionComposition
FunctionComposition (fc) is a simple header-based C++ library for composing functions.
It provides a simple and expressive way of combining program logic and routines, with support for lambdas, function objects and pure functions.
Example
A simple example with lambdas, using the (+) operator for composition:
using namespace fc;
auto sqare = [](float x) { return x*x; };
auto halve = [](float x) { return .5f*x; };
auto inv_square = [](float x) { return std::sqrtf(x); };
auto inv_halve = [](float x) { return 2.f*x; };
auto square_halve = square + halve;
auto inv_square_halve = inv_halve + inv_square;
auto ident = inv_square_halve + squave_halve;
assert(square_halve(6.f) == 9.f);
assert(inv_square_halve(9.f) == 6.f);
assert(ident(10.0f) == 10.0f);
A more complicated example, without the (+) for composition:
using namespace fc;
// polar coordinate r = sqrt(x*x+y*y)
auto r1 = compose(std::sqrtf, [](float x, float y) { return x*x + y*y; });
r1(1.f, 2.f);
auto square = [](float x) { return x*x; };
auto add = [](float x, float y) { return x + y; };
auto sqrt = [](float x) { return std::sqrtf(x); };
// r = f(g(h(x),h(y))) where f = sqrt, g = add, h = square
auto r2 = compose(sqrt, compose2(add, square, square));
r2(1.f, 2.f);
Documentation
Please see the file called INSTALL for usage details.
Several samples and tests are included with the source; together with CMake, these can be built and run
with any compatible compiler (developed with VC10, tested on GCC 4.6).
Licensing
MIT. Please see the file called LICENSE.
Contributions
This projet was loosely inspired by Eric Niebler's blog post "Fun with Function Composition" over at Expressive C++ (http://cpp-next.com/archive/2010/11/expressive-c-fun-with-function-composition/). fc goes somewhat further, allowing multiple arguments at any level in the composition, with arbitrary return types.