Rheolef  7.1
an efficient C++ finite element environment
functor.h
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1 #ifndef _RHEOLEF_FUNCTOR_H
2 #define _RHEOLEF_FUNCTOR_H
3 //
4 // This file is part of Rheolef.
5 //
6 // Copyright (C) 2000-2009 Pierre Saramito
7 //
8 // Rheolef is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 2 of the License, or
11 // (at your option) any later version.
12 //
13 // Rheolef is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
17 //
18 // You should have received a copy of the GNU General Public License
19 // along with Rheolef; if not, write to the Free Software
20 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 //
22 // ==========================================================================
23 //
24 // utiities for field expressions
25 //
26 // author: Pierre.Saramito@imag.fr
27 //
28 // date: 4 september 2015
29 //
30 
31 /*Class:functor
32 NAME: @code{functor} - a function wrapper suitable for field expressions
33 DESCRIPTION:
34  @noindent
35  A @emph{functor} is a class-function, i.e. a class that defines
36  the @code{operator()}:
37  it can be used in place of an usual function.
38  Moreover, functors can be used in Rheolef field expressions, mixed
39  with fields (see @ref{field class}).
40  For instance, assuming that @code{uh} is a field and @code{u_ex} is a functor:
41  @example
42  Float err_l1 = integrate (omega, abs(uh - uh_ex), qopt);
43  @end example
44  where @code{omega} denotes a mesh
45  (see @ref{geo class})
46  and @code{qopt} a quadrature formula
47  (see @ref{quadrature_option class}).
48  See also the @ref{integrate algorithm} function.
49  An usual function @code{u_ex_f} cannot always be mixed so nicely
50  in expressions, due to c++ language rules.
51  For instance, the following exprtession is valid:
52  @example
53  Float err_l1 = integrate (omega, abs(uh - u_ex_f), qopt);
54  @end example
55  In some case, the compiler cannot build a field expression using
56  usual functionsn e.g.
57  @example
58  Float I = integrate (omega, 0.5*u_ex_f), qopt);
59  @end example
60  because @code{0.5*u_ex_f} is a direct algebraic operation between
61  usual functions and flmoating points, that is not defined in the
62  c++ language.
63  A way to circumvent this difficulty is to convert the usual function
64  into a functor, as in:
65  @example
66  Float I = integrate (omega, 0.5*functor(u_ex_f)), qopt);
67  @end example
68 AUTHOR: Pierre.Saramito@imag.fr
69 DATE: 12 march 2013
70 End:
71 */
72 #include "rheolef/compiler.h"
73 
74 namespace rheolef {
75 
76 //<doc:
77 template<class R, class... Args>
78 std::function<R(Args...)>
79 functor (R(*f)(Args...)) {
80  return std::function<R(Args...)>(f);
81 }
82 //>doc:
83 } // namespace rheolef
84 #endif // _RHEOLEF_FUNCTOR_H
mkgeo_ball.f
int 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