Chapter 1. Egg 0.90.3

Unlike other modern languages, it is very difficult to make a function in C++ especially if you want to support Boost.ResultOf and Boost.Lambda. Egg is a small header-only framework of building functions, and offers higher-order functions.

#include <pstade/egg/pipable.hpp>
using namespace pstade::egg;

// This adaptation incurs no runtime overhead.
result_of_pipable<int(*)(int)>::type const
    to_upper = PSTADE_EGG_PIPABLE(&toupper);

void test()
{
    int maybeI = 'i'|to_upper|pipable(&tolower)|to_upper();
    BOOST_CHECK(maybeI == 'I');
}

Requirements

Boost C++ Libraries Version 1.34.0 or later (build not required)
P-Stade C++ Libraries Version 1.03.9 or later (build not required)

Portability

Egg is known to work on the following platforms:

Microsoft Visual C++ .NET Version 7.1 SP1
Microsoft Visual C++ 2005 Express Edition SP1
MinGW with GCC 3.4.4
MinGW with GCC 4.1.2
Intel C++ Compiler Professional Edition 10.1 for Windows

Rationale

Egg works around The Forwarding Problem.
Egg framework provides a way of static initialization if possible.

Acknowledgements

Special thanks to David Abrahams. The Forwarding Problem workaround is based on his callable.
Special thanks to Eric Niebler, who pointed out importance of static initialization.
Special thanks to Cryolite, Takeshi Mouri, yotto-k and Yusuke Kajimoto. These people are instrumental in the design and development of Egg.

Notation

This document uses the following notation.

Valid expression	Semantics
`_decltype`	An imaginary operator which is the same as `decltype` of C++0x.
`_typeof(a)`	`boost::remove_cv<boost::remove_reference<_decltype(a)>::type>::type`
`_const(a)`	`static_cast<_typeof(a) const>(a)`
`_pfo`	A Polymorphic Function Object
`_PFo`	A Polymorphic Function Object type which is neither reference nor cv-qualified.
`_lit`	A Little Function object
`_Lit`	A Little Function type which is neither reference nor cv-qualified.
`_Stg`	A type which is one of the Forwarding Strageties.
`_default`	`boost::use_default`
`_TUPLE_MAX_SIZE`	`10`
`++`	An imaginary operator to concatenate tokens.

Also, assume that every expression is placed after:

namespace egg = pstade::egg;
using namespace egg;