Adding a new function to an existing file

Here we describe how to add new function to an existing file.

Lets take the same example as before: we want to add the functinos that takes two numbers, A and B and computes A^2+B^2.

• In libpolys/coeffs/numbers.h add the line

    number n_myAdd(number A, number B, const coeffs R);

• In libpolys/coeffs/numbers.cc add the function:

  number n_myAdd(number A, number B, const coeffs R)
  {
    number AA = n_Mult(A, A, R),
    BB = n_Mult(B, B, R),
    CC = n_Add(AA, BB, R);
    n_Delete(&AA, R);
    n_Delete(&BB, R);
    return CC;
  }

  (Be sure you understand the memory management, in particular, the reason for the calls to n_Delete())

• Now, after a compile, the function is ready to use - however, it is not yet available in the interpreter.

• Next, we'll show how to incorporate this function - in the previous example we "hacked" it into the Singular/extra.cc file, now we'll do it properly.

  You need to add entries to

  • In Singular/tok.h: MYADD_CMD, (it is not important, but try to keep the list alphabetically sorted)

  • In Singular/table.h:

    • in cmdnames cmds[] add in the correct (alphabetical) position:

      "myAdd", 0, MYADD_CMD , CMD_2

      (where CMD_2 indicates that we take to arguments)

    • find sValCmd2 dArith2 and add

      ,{D(jjMyAdd), MYADD_CMD, NUMBER_CMD, NUMBER_CMD, NUMBER_CMD, ALLOW_PLURAL | ALLOW_RING}

  • In Singular/iparith.cc add a function

    static BOOLEAN jjMyAdd(leftv res, leftv u,leftv v)
    {
        number a=(number)u->Data();
        number b=(number)v->Data(),
        number c = n_myAdd(a,b,currRing);
        res ->data = (char *)c;
        return FALSE;
    }

    Note that the declaration in sValCmd2 guarantees that jjMyAdd is going to get called with 2 arguments, both of type number. Q: does iparith have to be in some special order?

    After a compile, you should have a new function in Singular: myAdd. Try using

    ring r=0,x,dp;
    number a =1;
    number b=2;
    myAdd(a,b);