Function rCompose

Singular/ipshell.cc:2780–3057

}

ring rCompose(const lists  L, const BOOLEAN check_comp, const long bitmask,const int isLetterplace)
{
  if ((L->nr!=3)
#ifdef HAVE_PLURAL
  &&(L->nr!=5)
#endif
  )
    return NULL;
  int is_gf_char=0;
  // 0: char/ cf - ring
  // 1: list (var)
  // 2: list (ord)
  // 3: qideal
  // possibly:
  // 4: C
  // 5: D

  ring R = (ring) omAlloc0Bin(sip_sring_bin);

  // ------------------------------------------------------------------
  // 0: char:
  if (L->m[0].Typ()==CRING_CMD)
  {
    R->cf=(coeffs)L->m[0].Data();
    R->cf->ref++;
  }
  else if (L->m[0].Typ()==INT_CMD)
  {
    int ch = (int)(long)L->m[0].Data();
    assume( ch >= 0 );

    if (ch == 0) // Q?
      R->cf = nInitChar(n_Q, NULL);
    else
    {
      int l = IsPrime(ch); // Zp?
      if( l != ch )
      {
        Warn("%d is invalid characteristic of ground field. %d is used.", ch, l);
        ch = l;
      }
      #ifndef TEST_ZN_AS_ZP
      R->cf = nInitChar(n_Zp, (void*)(long)ch);
      #else
      mpz_t modBase;
      mpz_init_set_ui(modBase,(long) ch);
      ZnmInfo info;
      info.base= modBase;
      info.exp= 1;
      R->cf=nInitChar(n_Zn,(void*) &info); //exponent is missing
      R->cf->is_field=1;
      R->cf->is_domain=1;
      R->cf->has_simple_Inverse=1;
      #endif
    }
  }
  else if (L->m[0].Typ()==LIST_CMD) // something complicated...
  {