How to compile using LoopTools in C++ - c++

Question

I am trying to use the following tool for C++ which is called LoopTools: http://www.feynarts.de/looptools/
It basically gives a numerical value for some integrals.
The manual says that in order to use it I must:
Like in the Fortran case, it saves a lot of typing to specify the location of LoopTools
once in an environment variable. For example, in the tcsh, use
setenv LT $HOME/LoopTools/(hosttype)
Then compile the programs that use LoopTools with the following command: $LT/bin/fcc -I$LT/include (source files) -L$LT/lib -looptools
I tried doing this with the example code they provide:
#include <iostream>
#include "clooptools.h"
int main() {
ltini();
cout << B0(1000., 50., 80.) << endl;
ltexi();
}
I saved this code as "example.cpp" and tried compiling it using what they said, namely:
g++ example.cpp $LT/bin/fcc -I$LT/include -L$LT/lib -looptools
But I get the following
.../LoopTools-2.16/x86_64-Linux/bin/fcc: file not recognized: file format not recognized
collect2: error: ld returned 1 exit status
What should I do?

Answer 1

To me, it works with the following changes (Ubuntu 20.04, x86_64, LoopTools-2.16).
Insert the following line,
using namespace::std;
to your example.cpp, before the use of cout/endl.
In $LT/bin/fcc, at line 19, remove the -stdlib=libstdc++ compiler flag from the cxx variable, which seems invalid for g++:
cxx="${REALCXX:-g++ -O3 -g -fomit-frame-pointer -ffast-math -fPIC -Wall -m64}"
In $LT/bin/fcc, at line 53, add .cpp as a C++ file suffix:
*.cc|*.cpp)
Otherwise, you need to rename your example file to example.cc.
As you noticed, the library is installed into $LT/lib64 on 64-bit Linux. Compile the program with
$LT/bin/fcc -I$LT/include example.cpp -L$LT/lib64 -looptools