# Plugin with 13 parameters

**URL:** <https://community.freefem.org/t/plugin-with-13-parameters/1732>\
**Category:** General Discussion\
**Created:** [May 11, 2022, 9:27am UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732 "2022-05-11T09:27:00Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![e-aranda](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/e-aranda/32/59_2.png) [@e-aranda](https://community.freefem.org/u/e-aranda)\
**Post date:** [May 11, 2022, 9:27am UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732/1 "2022-05-11T09:27:00Z")

</div>

Hello,  
I am trying to build some C++ function to link with FreeFem++. Something like: (dummy example)

“”"  
#include  
using namespace std;  
#include “error.hpp”  
#include “AFunction.hpp”  
#include “AFunction\_ext.hpp”

int example(const long &n1, const long &n2, const long &n3, KN \*const &vec1, KN \*const &vec2, KN \*const &vec3, KN \*const &vec4, KN \*const &vec5)  
{  
int M = vec2-\>N();  
cout \<\< "n1 : " \<\< n1 \<\< endl;  
cout \<\< "n2 : " \<\< n2 \<\< endl;  
cout \<\< "n2 : " \<\< n3 \<\< endl;  
for (int i=0;i\<M;i++) // do some stuff with some vectors  
{  
\*(vec1[0]+i)= \*(vec1[0]+i) + 1;  
_(vec2[0]+i)=_(vec2[0]+i) \* \*(vec2[0]+i);  
\*(vec3[0]+i)= \*(vec3[0]+i) - 3.;  
}  
return 0;  
}

class Init {  
public:  
Init();  
};

Init init;  
Init::Init(){  
Global.Add(“exfun”,"(",new OneOperator8\_\< int, long, long, long, KN_, KN_, KN_,KN_, KN\* \>(example));  
}  
“”"  
but I need 13 parameters in my example function, and there is no OneOperatorX\_, for X\>8. How can I do it?

Thanks,  
Ernesto

---

<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [May 11, 2022, 10:06am UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732/2 "2022-05-11T10:06:15Z")

</div>

You could you use a `KN<long>` for the `n[1-3]` and a `KN<KN<K>>` for the `vec[1-5]`? Not ideal, but it gets. the job done.

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<div class="post-metadata">

**Author:** ![e-aranda](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/e-aranda/32/59_2.png) [@e-aranda](https://community.freefem.org/u/e-aranda)\
**Post date:** [May 11, 2022, 10:57am UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732/3 "2022-05-11T10:57:56Z")

</div>

Thanks Pierre,

but now I don’t know how to pass data to my function. If I define a  
`real[int,int]` in .edp file to pack my vectors and use `KN<KN<double>*>*`  
I am getting a Segment fault.

I have also tried to use a `KNM<double>*` and it works, but now, I don’t know how to unpack this matrix in vectors. Indeed, what I need is that every column of the matrix is a double \*

Any hints?

---

<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [May 11, 2022, 11:18am UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732/4 "2022-05-11T11:18:02Z")

</div>

You should be able to go from `KNM<K>` to `KN<K>` back and forth using the following syntax: [FreeFem-sources/SLEPc-code.hpp at master · FreeFem/FreeFem-sources · GitHub](https://github.com/FreeFem/FreeFem-sources/blob/master/plugin/mpi/SLEPc-code.hpp#L470-L471). This sets the i th column, but should work to get it instead.

---

<div class="post-metadata">

**Author:** ![e-aranda](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/e-aranda/32/59_2.png) [@e-aranda](https://community.freefem.org/u/e-aranda)\
**Post date:** [May 11, 2022, 11:43am UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732/5 "2022-05-11T11:43:59Z")

</div>

Many many thanks!!!

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<div class="post-metadata">

**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [May 12, 2022, 3:33pm UTC](https://community.freefem.org/t/plugin-with-13-parameters/1732/6 "2022-05-12T15:33:36Z")

</div>

To the only way is to add a two class like form 13 parameter,  
I think with c++20 or better you can use variadic templates , or tuples …

```auto
template<class R,class A0,class A1,class A2, class A3, class A4, class A5, class A6, class A7, class E=E_F0> // extend AX
class E_F_F0F0F0F0F0F0F0F0_ :public E { public: // extend 
   typedef R (*func)(const A0 &,const A1 & , const A2 &, const A3 &, const A4 &, const A5 &, const A6 &, const A7 & ) ; // extend AX
  func f;
  Expression a0,a1,a2,a3,a4,a5,a6,a7; // extend aX
  E_F_F0F0F0F0F0F0F0F0_(func ff, // extend F0
			Expression aa0,
			Expression aa1,
			Expression aa2,
			Expression aa3,
			Expression aa4,
			Expression aa5,
			Expression aa6,
			Expression aa7) // extend 
    : f(ff), a0(aa0), a1(aa1), a2(aa2), a3(aa3), a4(aa4), a5(aa5), a6(aa6), a7(aa7) {} // extend aX
  AnyType operator()(Stack s) const 
    {return SetAny<R>( f( GetAny<A0>((*a0)(s)),
			  GetAny<A1>((*a1)(s)),
			  GetAny<A2>((*a2)(s)),
			  GetAny<A3>((*a3)(s)),
			  GetAny<A4>((*a4)(s)),
			  GetAny<A5>((*a5)(s)),
			  GetAny<A6>((*a6)(s)),
			  GetAny<A7>((*a7)(s)) ) );} // extend aX
  virtual size_t nbitem() const {return a7->nbitem(); } // modif
      bool MeshIndependent() const 
      {return E::MeshIndependent() && a0->MeshIndependent() && a1->MeshIndependent()&& a2->MeshIndependent()
	 && a3->MeshIndependent()&& a4->MeshIndependent()&& a5->MeshIndependent()&& a6->MeshIndependent()&& a7->MeshIndependent();} // extend aX

};

template<class R,class A=R,class B=A,class C=B, class D=C ,class E=D ,class F=E ,class G=F ,class H=G , class CODE=E_F_F0F0F0F0F0F0F0F0_<R,A,B,C,D,E,F,G,H,E_F0> > // extend  
class OneOperator8_ : public OneOperator { // 3->4
  aType r; // return type 
    typedef typename CODE::func func;
  func f;
public: 
  E_F0 * code(const basicAC_F0 & args) const 
    {  
	if ( args.named_parameter && !args.named_parameter->empty() ) 
	    CompileError( " They are used Named parameter ");
	
	return new CODE(f,
		     t[0]->CastTo(args[0]),
		     t[1]->CastTo(args[1]),
		     t[2]->CastTo(args[2]),
		     t[3]->CastTo(args[3]),
		     t[4]->CastTo(args[4]),
		     t[5]->CastTo(args[5]),
		     t[6]->CastTo(args[6]),
		     t[7]->CastTo(args[7]));} // extend
  OneOperator8_(func ff): // 3->4
    OneOperator(map_type[typeid(R).name()],
		map_type[typeid(A).name()],
		map_type[typeid(B).name()],
		map_type[typeid(C).name()],
		map_type[typeid(D).name()],
		map_type[typeid(E).name()],
		map_type[typeid(F).name()],
		map_type[typeid(G).name()],
		map_type[typeid(H).name()]), // extend
    f(ff){}
};

```