/****************************************************
*  This program multiplies a polynomial P(x) by a   *
*  polynomial Q(x)                                  *
* ------------------------------------------------- *
* Ref.: "Mathématiques en Turbo-Pascal By M. Ducamp *
* and A. Reverchon (vol 2), Eyrolles, Paris, 1988"  *
* [BIBLI 05].                                       *
* ------------------------------------------------- *
* SAMPLE RUN:                                       *
*                                                   *
* MULTIPLY TWO POLYNOMIALS:                         *
*                                                   *
* P(X) = x3 - 6x + 7                                *
* Q(x) = 5x5 -3x4 +x2 -3                            *
*                                                   *
* +5 X8 -3 X7 -30 X6 +54 X5 -21 X4 -9 X3  +7 X2     *
*                                                   *
* +18 X -21                                         *
*                                                   *
* ------------------------------------------------- *
* Functions used (of unit Polynoms):                *
*                                                   *
*  AddNumber(), EnterPolynom(), DisplayPolynom()    *
*  and MultNumber().                                *
*                                                   *
*                      C++ version by J-P Moreau.   *
*                  (To be linked with polynoms.cpp).*
*                          (www.jpmoreau.fr)        *
****************************************************/
#include <stdio.h>
#include <string.h>
#include <malloc.h>

#include "polynoms.h"


ar_polynom *P, *Q, *R;


// P(X) * Q(X) = R(X) - R can be either P or Q
bool MultPolynom(ar_polynom *P, ar_polynom *Q, ar_polynom *R) {
  int i,j, n;
  ar_number u;
  ar_polynom *nr;
  nr = (ar_polynom *) calloc(1,sizeof(ar_polynom));
  //verify that P and Q are not void
  if (P->degree==0 && P->coeff[0].value==0) return FALSE;
  if (Q->degree==0 && Q->coeff[0].value==0) return FALSE;
  nr->degree=P->degree+Q->degree;
  if (nr->degree>AR_MAXPOL) return FALSE;  // R degree is too big
  for (n=0; n<=nr->degree; n++)  {
    if (!SetNumber(&nr->coeff[n],"0")) return FALSE;
    for (i=0; i<=P->degree; i++) {
      j=n-i;
      if (j>=0 && j<=Q->degree) {
        if (!MultNumber(P->coeff[i],Q->coeff[j],&u)) return FALSE;
        if (!AddNumber(nr->coeff[n],u,&nr->coeff[n])) return FALSE;
      }
    }
  }
  //copy nr in R
  R->degree=nr->degree;
  for (i=0; i<=nr->degree; i++)  R->coeff[i]=nr->coeff[i];
  free(nr);
  return TRUE;
}


void main() {
  //dynamic memory allocation of polynomials
  P = (ar_polynom *) calloc(1,sizeof(ar_polynom));
  Q = (ar_polynom *) calloc(1,sizeof(ar_polynom));
  R = (ar_polynom *) calloc(1,sizeof(ar_polynom));
  printf("\n MULTIPLY TWO POLYNOMIALS:\n\n");
  if (!EnterPolynom(" P(X) = ", P)) return;
  if (!EnterPolynom(" Q(X) = ", Q)) return;
  printf("\n");
  if (MultPolynom(P,Q,R))
    DisplayPolynom(R);
  else
    printf(" Error in multiplication.\n");
  printf("\n\n");
  free(P); free(Q); free(R);
}

//end of file multpol.cpp