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<html>
<head>
<title>
C++_CALLS_F90 - C++ Main Program Calls FORTRAN90 Subroutines
</title>
</head>
<body bgcolor="#EEEEEE" link="#CC0000" alink="#FF3300" vlink="#000055">
<h1 align = "center">
C++_CALLS_F90 <br> C++ Main Program Calls FORTRAN90 Subroutines
</h1>
<hr>
<p>
<b>C++_CALLS_F90</b>
is a directory of C++ programs which
illustrates how a C++ main program can call a FORTRAN90 subroutine.
</p>
<p>
For this example, the KRONROD package is used. Note that the KRONROD
library is available in C++ and in FORTRAN90, so this example is not
created out of necessity (the C++ main program could have simply called
the C++ version of KRONROD). Instead, it is intended as an example of
how to do this when you have to (you don't have a C++ version of the
routines you want to use.)
</p>
<p>
When calling a FORTRAN90 routine from a C++ function, there are
some simple things that may be enough to guarantee success.
<ul>
<li>
a FORTRAN90 subroutine is like a C++ void function, and should
be declared this way in the C++ code. The qualifier <b>extern</b>
should also be used.
</li>
<li>
a FORTRAN90 subroutine or function expects all its arguments
to be passed by reference. This generally means simply that
the C++ function must pass scalar variables by reference, not value.
</li>
<li>
typically, when the FORTRAN90 compiler compiles the FORTRAN90
code, the names of functions and subroutines are stored with
an appended underscore. In order for these names to be found
by the C++ code, it is necessary that the C++ code declare and
invoke the FORTRAN90 functions and subroutines with the underscore
explicitly appended to the name.
</li>
<li>
in many cases, a FORTRAN90 compiler is simply a "front end" to a
corresponding C++ compiler, as in the case of the GNU compilers
gfortran and g++, or the Intel compilers ifort and icpp. This means
that, as long as the corresponding compilers are used to compile
the FORTRAN90 and C++ codes, it is probably possible to use either
compiler to link and load the object codes; however, the load
command may need to specify explicitly certain libraries associated
with one of the languages. For instance, if loading using the
gcc command, it is necessary to include "-l gfortran" so that
the FORTRAN90 I/O libraries, among others, are included in the build.
</li>
</ul>
</p>
<h3 align = "center">
Licensing:
</h3>
<p>
The computer code and data files described and made available on this web page
are distributed under
<a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
</p>
<h3 align = "center">
Languages:
</h3>
<p>
<b>C++_CALLS_F90</b> is available in
<a href = "../../c_src/c_calls_f90/c_calls_f90.html">a C version</a> and
<a href = "../../cpp_src/c++_calls_f90/c++_calls_f90.html">a C++ version</a> and
<a href = "../../m_src/matlab_calls_f90/matlab_calls_f90.html">a MATLAB version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../c_src/c_calls_f90/c_calls_f90.html">
C_CALLS_F90</a>,
C programs which
call a FORTRAN90 subroutine.
</p>
<p>
<a href = "../../cpp_src/c++_calls_c/c++_calls_c.html">
C++_CALLS_C</a>,
C++ programs which
call a C function.
</p>
<p>
<a href = "../../cpp_src/c++_calls_f77/c++_calls_f77.html">
C++_CALLS_F77</a>,
C++ programs which
call a FORTRAN77 subroutine.
</p>
<p>
<a href = "../../f_src/f90_calls_c++/f90_calls_c++.html">
F90_CALLS_C++</a>,
FORTRAN90 programs which
call a C++ function.
</p>
<p>
<a href = "../../cpp_src/kronrod/kronrod.html">
KRONROD</a>,
a C++ library which
can compute a Gauss and Gauss-Kronrod pair of quadrature rules
of arbitrary order,
by Robert Piessens, Maria Branders.
</p>
<p>
<a href = "../../f_src/kronrod/kronrod.html">
KRONROD</a>,
a FORTRAN90 library which
can compute a Gauss and Gauss-Kronrod pair of quadrature rules
of arbitrary order,
by Robert Piessens, Maria Branders.
</p>
<p>
<a href = "../../cpp_src/mixed/mixed.html">
MIXED</a>,
C++ programs which
call a function written in another programming language.
</p>
<h3 align = "center">
Reference:
</h3>
<p>
<ul>
<li>
<a href = "../../pdf/keinert.pdf">
Calling FORTRAN Subroutines from Fortran, C and C++</a>,<br>
Fritz Keinert,<br>
Mathematics Department,<br>
Iowa State University.
</li>
</ul>
</p>
<h3 align = "center">
Source Code:
</h3>
<p>
<b>KRONROD</b> is the FORTRAN90 source code for the KRONROD library.
It should be essentially unchanged from the standard version.
<ul>
<li>
<a href = "kronrod.f90">kronrod.f90</a>;
</li>
</ul>
</p>
<p>
<b>KRONROD_PRB</b> is the C++ source code for the main program.
Some changes have been made from the standard version in order
to adjust for the fact that we are calling a FORTRAN77 subroutine.
<ul>
<li>
<a href = "kronrod_prb.cpp">kronrod_prb.cpp</a>;
</li>
</ul>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
<ul>
<li>
<a href = "kronrod_prb.sh">kronrod_prb.sh</a>,
commands to compile, link, load and run the program;
</li>
<li>
<a href = "kronrod_prb_output.txt">kronrod_prb_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
You can go up one level to <a href = "../cpp_src.html">
the C++ source codes</a>.
</p>
<hr>
<i>
Last revised on 08 December 2010.
</i>
<!-- John Burkardt -->
</body>
</html>