public Polynomial mul(Polynomial poly) {
int deg = degree + poly.degree;
Number lcoeffs[] = new Number[deg + 1];
for (int i = 0; i <= deg; ++i) lcoeffs[i] = baseRing.getZERO();
for (int i = 0; i <= degree; ++i)
for (int j = 0; j <= poly.degree; ++j) {
lcoeffs[i + j] = baseRing.add(lcoeffs[i + j], baseRing.mul(coeffs[i], poly.coeffs[j]));
}
return valueOf(lcoeffs);
}
/**
* Construct a polynomial over a ring. In general the valueOf method should be used to construct a
* new polynomial.
*
* @param baseRing the underlying ring of the polynomial.
* @param symbol the symbol used to display the polynomial
* @param coeffs an array of coefficients in the base ring coeff[0] is constant, coeff[1] is
* coefficient of t etc.
*/
public Polynomial(RingI baseRing, String symbol, Number coeffs[]) {
this.baseRing = baseRing;
this.symbol = symbol;
int deg = 0;
for (int i = coeffs.length - 1; i > 0; --i)
if (!baseRing.equals(coeffs[i], baseRing.getZERO())) {
deg = i;
break;
}
if (deg == coeffs.length - 1) this.coeffs = coeffs;
else {
this.coeffs = new Number[deg + 1];
System.arraycopy(coeffs, 0, this.coeffs, 0, deg + 1);
}
this.degree = deg;
}
public String toString() {
if (degree == 0) return coeffs[0].toString();
StringBuffer sb = new StringBuffer("");
for (int i = degree; i >= 0; --i) {
String s = coeffs[i].toString();
// don't bother if a zero coeff
if (s.equals("0") || this.baseRing.equals(coeffs[i], baseRing.getZERO())) continue;
// apart from first add a + sign if positive
if (i != degree && !s.startsWith("-")) sb.append("+");
// always print the final coeff (if non zero)
if (i == 0) {
String s1 = coeffs[i].toString();
sb.append(s1);
// if(s1.startsWith("(") && s1.endsWith(")"))
// {
// sb.append(s1.substring(1,s1.length()-1));
// }
// else sb.append(s1);
break;
}
// if its -1 t^i just print -
if (s.equals("-1")) sb.append("-");
else if (s.equals("1") || this.baseRing.equals(coeffs[i], baseRing.getONE())) {
} // don't print 1
else {
if (needsBrackets(coeffs[i].toString())) {
sb.append("(");
sb.append(coeffs[i].toString());
sb.append(")");
} else sb.append(coeffs[i].toString());
// sb.append(stripBrackets(coeffs[i]));
sb.append(" ");
}
if (i >= 2) sb.append(symbol + "^" + i);
else if (i == 1) sb.append(symbol);
}
sb.append("");
return sb.toString();
}
