Adding debugging screen output - BrentBaccala/Singular GitHub Wiki

Here we discuss how to add debugging screen output to an already present Singular function.

We assume that you are in the Sources directory.

• We add a screen output to the function n_Add (which adds two numbers):

  To do this, in the file libpolys/coeffs/coeffs.h change

  static inline number n_Add(number a, number b, const coeffs r) 
     { 
         assume(r != NULL); 
         assume(r->cfAdd!=NULL);  
         return r->cfAdd(a, b, r); 
     }
  

  into

  static inline number n_Add(number a, number b, const coeffs r)
     { 
          assume(r != NULL);
          assume(r->cfAdd!=NULL);
          Print("n_Add(a,b,r) called with argument a = ");
          n_Print(a,r); 
          PrintLn(); 
          return r->cfAdd(a, b, r); 
      }
  

• Compile Singular by doing make

• Start Singular by ./Singular/Singular

• Try out the screen output by doing

    ring r;
    number n=1;
    number m=2;
    n+m;
  

Warnings, why you should do this only for testing purposes and remove afterwards:

• one should never add such code the the n_-routines but to the specific npAdd, nlAdd etc.
• if one really want to catch all additions, patch jjPLUS_N in Singular/iparith.cc
• n_Print is a bad hack - it destroys the current output buffer, the correct routine for writing numbers is n_Write (which is a little bit uneasy to use because it outputs into a buffer, not the screen)