添加多项式

Question

我需要一些帮助。我正在做测试驱动的开发。这些是测试：

@Test public void add01() throws TError { assertEquals(new Term(10,5),  new Term(4,5).add(new Term(6,5))); }
@Test public void add02() throws TError { assertEquals(new Term(6,5),   new Term(0,5).add(new Term(6,5))); }
@Test public void add03() throws TError { assertEquals(new Term(2,5),   new Term(-4,5).add(new Term(6,5))); }
@Test public void add04() throws TError { assertEquals(new Term(10,0),  new Term(4,0).add(new Term(6,0))); }
@Test public void add05() throws TError { assertEquals(new Term(4,5),   new Term(4,5).add(new Term(0,5))); }
@Test public void add06() throws TError { assertEquals(new Term(-2,5),  new Term(4,5).add(new Term(-6,5))); }

@Test (expected = IncompatibleTerms.class)
public void add07() throws TError { t = new Term(4,5).add(new Term(6,0)); }

@Test (expected = CoefficientOverflow.class)
public void add08() throws TError { t = new Term(min,4).add(new Term(-1,4)); }

@Test public void add09() throws TError { assertEquals(new Term(min,4), new Term(min+1,4).add(new Term(-1,4))); }
@Test public void add10() throws TError { assertEquals(new Term(-11,4), new Term(-10,4).add(new Term(-1,4))); }
@Test public void add11() throws TError { assertEquals(new Term(-2,4),  new Term(-1,4).add(new Term(-1,4))); }
@Test public void add12() throws TError { assertEquals(new Term(-1,4),  new Term(0,4).add(new Term(-1,4))); }
@Test public void add13() throws TError { assertEquals(Term.Zero,       new Term(1,4).add(new Term(-1,4))); }
@Test public void add14() throws TError { assertEquals(new Term(9,4),   new Term(10,4).add(new Term(-1,4))); }
@Test public void add15() throws TError { assertEquals(new Term(max,4), new Term(max-1,4).add(new Term(1,4))); }

@Test (expected = CoefficientOverflow.class)
public void add16() throws TError { t = new Term(max,4).add(new Term(1,4)); }

//Using domain-specific knowledge:  addition should be commutative

@Test public void add17() throws TError { assertEquals(new Term(-1,2).add(new Term(1,2)),       new Term(1,2).add(new Term(-1,2))); }
@Test public void add18() throws TError { assertEquals(new Term(min+1,2).add(new Term(-1,2)),   new Term(-1,2).add(new Term(min+1,2))); }
@Test public void add19() throws TError { assertEquals(new Term(min,2).add(Term.Zero),      Term.Zero.add(new Term(min,2))); }
@Test public void add20() throws TError { assertEquals(new Term(min,0).add(Term.Unit),      Term.Unit.add(new Term(min,0))); }
@Test public void add21() throws TError { assertEquals(new Term(max,0).add(Term.Zero),      Term.Zero.add(new Term(max,0))); }
@Test public void add22() throws TError { assertEquals(new Term(max-1,2).add(new Term(1,2)),    new Term(1,2).add(new Term(max-1,2))); }
@Test public void add23() throws TError { assertEquals(new Term(max,2).add(new Term(min,2)),    new Term(min,2).add(new Term(max,2))); }

这是我迄今为止在“Andrej Gajduk”的帮助下的添加方法。

public Term add(Term that) throws CoefficientOverflow, IncompatibleTerms {
    if (this.expo != that.expo) throw new IncompatibleTerms();
    return new Term (this.coef + that.coef,expo);
}

这些是失败的测试 = 2、5、8、12、16、19、21。但我对测试 17-23 有疑问；我知道他们中的一些人通过了，但我认为他们不应该，因为这就像 x + y = y + x，但我不知道如何实现它。

我需要有关此测试失败原因的一些帮助/指导。

对于测试 8 和 16，我尝试了以下代码。它完成了这项工作，但随后在其他测试中产生了更多错误。那么所有的失败都变成了 2, 5, 8, 12, 16, 19, 21 + 20, 23（两个额外的失败）

if (this.coef == Integer.MIN_VALUE || that.coef == Integer.MIN_VALUE) throw new CoefficientOverflow();
if (this.coef == Integer.MAX_VALUE || that.coef == Integer.MAX_VALUE) throw new CoefficientOverflow();

Answer 1

此链接显示了检测溢出的另一种方法：http://mindprod.com/jgloss/gotchas.html#OVERFLOW

我认为这是因为当 coef 为 0 或整个语句被假定为零时，因此您需要检查这一点并使用零的替代项

if(this.coef ==0)
{//return Term t = new Term(that.coef, that.expo);}

else
{//return Term t = new Term(this.coef, this.expo);}
}

希望对你有帮助

Answer 2

您的equals 方法不正确。请更新如下：

@Override
public boolean equals(Object that) {
    if (that == null) {
        return false;
    }else if (this.getClass() != that.getClass()) {
        return false;
    }else if (this == that) {
        return true;
    }else{
        Term term = (Term) that;
        if ((term.coef) == (this.coef) && (term.expo) == (this.expo)) {
            return true;
        }
    }
    return false;
}

为了让你通过大部分测试用例，更新add方法如下：

public Term add(Term that) throws IncompatibleTerms, CoefficientOverflow{
    //handle addition with term zero
        if(this.equals(Term.Zero)){
        return that;
    }else if(Term.Zero.equals(that)){
        return this;
    }

    if (this.expo != that.expo) throw new IncompatibleTerms();
    if((this.coef>= 0 && that.coef >= 0 && this.coef + that.coef <0) ||
            (this.coef<= 0 && that.coef <= 0 && this.coef + that.coef >0)){
                         throw new CoefficientOverflow();
        }    
    return new Term (this.coef + that.coef,expo);
}