`xtd`

what's that?

xtd is a tiny replacement (a single file of about 1.6k lines) for the functional (and cmath) header(s) of the standard C++ library. If you've got any problem with it please submit a bug report.

related works

Some functional libraries are available for people who want to express functional pieces of code in C++: FC++ by Brian McNamara and Yannis Smaragdakis, FACT! by Jörg Striegnitz, and the Boost Lambda Library by Jaakko Järvi and Gary Powell. They provide much more functional features than we do, so we clearly do not pretend to replace those libraries. Instead we propose the smallest subset (just one file!) that allows to write functions in a very convenient way when using some std algorithms. The way we have designed classes in xtd relies on the static C++ object-oriented paradigm (SCOOP) as described here.

authors

Thierry Géraud (corresponding author

), Matthieu Baechler, Christopher Faulet, and Sébastien Lagarde.

sample use

std C++	xtd
remove_if(L.begin(), L.end(), compose2(logical_and<bool>(), bind2nd(greater<int>(), 100), bind2nd(less<int>(), 1000)));	remove_if(L.begin(), L.end(), x > 100 && x < 1000);

readme

Get the files and follow the proposed tour. This code compiles with:

GNU g++ version 3.3 and greater (g++ -Wall -ansi -pedantic tour.cc)
Intel(R) icc version 7.1 (icc -w1 -Xc tour.cc)
Comeau Computing como version 4.3.3 (como -lm -DXTD_USE_COMO tour.cc)

last snapshot

2004-feb-10: xtd.h tour.cc

features

2004-feb-10:

compile with como but require the macro definition: -DXTD_USE_COMO
provide disambiguated math function names; e.g., xcos in addition to cos, etc.

2004-feb-06:

add some explicit error messages; e.g., try cos(x,x)
expression prettyprint capabilities; e.g., try std::cout << to<int>(pow(cos,2) + pow(sin,2))(x) << std::endl

2004-feb-04:

provide (almost) all C99/C++ math function objects
support functions without argument in expression (e.g., rand)

2004-jan-30:

provide math function objects following the std ones:
- xtd::cos(x) is an expression
- xtd::cos(x)(51) evaluates the expression
first and second are access functions to pair-like class members



2004-jan-25:

predicate expressions support true and false: (true == x) is ok
proper use of std::for_each's return: f = for_each(i1,i2, fun(f)(x + 1)) is ok if f is a function object
support for ternary expression: ternary(x, 1+y, 1-y) with x expecting bool data works fine



2004-jan-24:

definition of traits for expression return type
support for function expressions through xtd::fun(..)
expressions accept expressions as argument: for instance (2*x)(x+1) means (2*(x+1)) and (x*y+1)(3*x, x+2) means ((3*x)*(x+2)+1)
expressions accept some constant values (the ones whose type is int, float, or double)
    without precising cst(..)

type promotion: (x + 3.14f) with x being a placeholder for int data will give float
ability to define meta-function objects (such as struct sqr { template<class T>  T operator()(T t) const {return t*t;} };) and to involve them in expressions: fun(sqr)(x + 1) is ok


first draft (2002):

expressions mimics and rely on the unary or binary std ones
expressions derive from expr (so that expression templates are disambiguated)
constants in expressions need to be wrapped with cst
sample code is: cst(2) * x + cst(1)
known problem: type promotion is not handled





 

to-do list

handle methods (such as std::mem_ptr does)
handle complex and array types in expressions
test with other compilers/platforms than g++ and icc
address performance issues (in particular, ensure that nrvo is effective)
write a user guide
write a conception white paper
add "motivation / related works / thanks" section to this page
then start an alpha-test process...