functor.h
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#ifndef _RHEOLEF_FUNCTOR_H
#define _RHEOLEF_FUNCTOR_H
//
// This file is part of Rheolef.
//
// Copyright (C) 2000-2009 Pierre Saramito
//
// Rheolef is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// Rheolef is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Rheolef; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// ==========================================================================
//
// utiities for field expressions
//
// author: Pierre.Saramito@imag.fr
//
// date: 4 september 2015
//
/*Class:functor
NAME: @code{functor} - a function wrapper suitable for field expressions
DESCRIPTION:
@noindent
A @emph{functor} is a class-function, i.e. a class that defines
the @code{operator()}:
it can be used in place of an usual function.
Moreover, functors can be used in Rheolef field expressions, mixed
with fields (see @ref{field class}).
For instance, assuming that @code{uh} is a field and @code{u_ex} is a functor:
@example
Float err_l1 = integrate (omega, abs(uh - uh_ex), qopt);
@end example
where @code{omega} denotes a mesh
(see @ref{geo class})
and @code{qopt} a quadrature formula
(see @ref{quadrature_option class}).
See also the @ref{integrate algorithm} function.
An usual function @code{u_ex_f} cannot always be mixed so nicely
in expressions, due to c++ language rules.
For instance, the following exprtession is valid:
@example
Float err_l1 = integrate (omega, abs(uh - u_ex_f), qopt);
@end example
In some case, the compiler cannot build a field expression using
usual functionsn e.g.
@example
Float I = integrate (omega, 0.5*u_ex_f), qopt);
@end example
because @code{0.5*u_ex_f} is a direct algebraic operation between
usual functions and flmoating points, that is not defined in the
c++ language.
A way to circumvent this difficulty is to convert the usual function
into a functor, as in:
@example
Float I = integrate (omega, 0.5*functor(u_ex_f)), qopt);
@end example
AUTHOR: Pierre.Saramito@imag.fr
DATE: 12 march 2013
End:
*/
#include "rheolef/compiler.h"
namespace rheolef {
//<doc:
template<class R, class... Args>
std::function<R(Args...)>
functor (R(*f)(Args...)) {
return std::function<R(Args...)>(f);
}
//>doc:
} // namespace rheolef
#endif // _RHEOLEF_FUNCTOR_H
mkgeo_ball.f
f
Definition: mkgeo_ball.sh:221
rheolef::functor
std::function< R(Args...)> functor(R(*f)(Args...))
Definition: functor.h:79
rheolef
This file is part of Rheolef.
Definition: compiler_eigen.h:37
f
Definition: cavity_dg.h:29