参观湖北省反腐倡廉警示教育基地有感

1、Chapter 13Operator Overloading(运算符重载13.1 Introduction13.2 Operator Functions13.3 Overloading Simple Operators13.4 Overloading “13.5 Overloading “13.6 Object conversion13.7 Overloading “= 13.8 Overloading “() and Functor13.1 IntroductionOperators 运算符How about object variables?String operators2string

2、s1 = ABC;string s2 = s1 + DEF;couts1endl;couts2)endl;.int a = 1;int b = a+1;if(ab) couta;class C;C c, a, b;c = a + b;/?The Rational Class 分数31/2, 1/3, 11/12,3 4 23 84 7 32 9baRational.cppRunRational.hTestRationalClass.cpp分子分母Operation of the Rational Class4Rational Rational:add(Rational &secondRatio

3、nal) long n = numerator * secondRational.getDenominator() + denominator * secondRational.getNumerator();long d = denominator * secondRational.getDenominator();return Rational(n, d);Rational Rational:subtract(Rational &secondRational)long n = numerator * secondRational.getDenominator() - denominator

4、* secondRational.getNumerator();long d = denominator * secondRational.getDenominator();return Rational(n, d); coutr1.toString() + r2.toString() = r1.add(r2).toString() endl; coutr1.toString() - r2.toString() = r1.subtract(r2).toString() endl; cout r1 + r2 = r1+r2 endl; cout r1 - r2 = r1-r2 endl; Ope

5、rator Functions 运算符函数The functions to overload operators5bool Rational:operatorcompareTo(secondRational) 0) return true; else return false;if(r1 r2) cout“r1 is less than r2.endl;if(r1.operator(r2) cout“r1 is less than r2.endl;Overloadable Operators 6Unoverloadable Operators: . *? :#13.3 Overloading

6、Simple OperatorsRelational Operators7bool Rational:operatorcompareTo(secondRational) 0) return true; else return false;bool Rational:operator (Rational &secondRational)long n = numerator * secondRational.getDenominator() denominator * secondRational.getNumerator();if (n 0) return true; else return f

7、alse; A member function of Rational class.Parameter: usually pass-by-reference (can by value) one for a binary operator (The other one the object of the function)keywordReturn type: the data type of “add(secondRational);Return type: Rational, the data type of “+To be used as an operand in complex op

8、eration!NotesThe left operand is fixed to be the operating object automatically c1 = c2 + c3 ; c1 = c2.operator+(c3); The number of parameters is determined by the operator itselfYou cannot change itOverloading does not change the operator precedence 优先级 and associativity 结合性The (return) type of the

9、 operator function can be defined by youUsually the same class type to be operational in complex operation9Overloading Shorthand Operators10+=, -=, *=, /= Rational Rational:operator+=(Rational &secondRational) *this = this-add(secondRational); return (*this);Rational r1(2, 4);Rational r2 = r1 += Rat

10、ional(2, 3);cout r1 is r1.toString() endl;cout r2 is r2.toString() endl;Overloading Unary Operators 11+ and - -no parametersRational Rational:operator-() numerator *= -1; return *this;Overloading + and -Prefix vs. Postfix12+r1r1+Rational Rational:operator+() numerator += denominator; return *this; R

11、ational Rational:operator+() Rational temp(numerator, denominator); numerator += denominator; return temp;(int dummy)Same signature,How to distinguish them?哑元参数,the value is never used;It must be “int.Same signature,How to distinguish them?13.4 Overloading “The array subscript is an operator You can

12、 overload this operator to access the contents of the object using the array-like syntax For example, r0: to access numerator r1: to access denominator13Overloading “ 14long Rational:operator(const int &index) if (index = 0) return numerator; else if (index = 1) return denominator; else cout subscri

13、pt error endl; exit(0); Accessor and MutatorThe operator functions as both accessor and mutator. After adding this operator to the Rational class, the Rational class is mutable.15Rational r4(1, 2); r40 = 3; r41 = 4;long &Rational:operator(const int &index)13.5 Overloading “: stream extraction operat

14、orFor reading values from cinOverload them?16Rational r4(1, 2); coutr40endl;coutr41endl;Rational r4(1, 2); coutr4;Overloading “17Rational r4(1, 2); coutr4;Rational Rational:operator (?) Rational Rational:operator (ostream &str, Rational &rational) !The left operand is fixed to be the operating objec

15、t automatically:Rational Rational:operator+(Rational &);an instance of ostreamThen, how to do?Overloading “Making use of friendship!18 friend ostream &operator(istream &, Rational &);ostream &operator(ostream &str, Rational &rational) str rational.numerator / (istream &str, Rational &rational) cout

16、rational.numerator; cout rational1; return str;Other operators can also be overloaded as friends!13.6 Object ConversionConvert a class type to other data types?Using operator functions19double i, j;i=4 + 5.5;double i;Rational r1;i= 2+r1;Object Conversion Rational:operator double() return 1.0 * getNu

17、merator() / getDenominator();20Rational r1(1, 4);double d = r1 + 5.1; cout r1 + 5.1 is d 60; ;int main()Comparer cmp;int i;cini;if(cmp(i) coutYes, passed!n;else cout60;Object acting as a functionFunction object (functor, 仿函数)Functor as ParameterTo count an integral arrays elements that satisfy some condition, e.g. =60 =85=9026int countArray(int a, int s, int th);int countArray(int a, int s);int countArrayIf(int a, int s, Comparer cmp);Functor as Parameter27class Comparerpublic: Comparer(int val = 60):vs(val) int