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solved operators exercise
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‎exercises/operators/operators.cpp

Lines changed: 110 additions & 80 deletions
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@@ -3,89 +3,119 @@
33
#include <numeric>
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class Fraction {
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public:
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// TODO: constructors and operators
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private:
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void normalize() {
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const int gcd = std::gcd(m_num, m_denom);
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m_num /= gcd;
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m_denom /= gcd;
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}
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unsigned int m_num, m_denom;
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public:
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Fraction() = delete;
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Fraction(int num)
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: m_num(num)
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, m_denom(1)
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{
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}
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Fraction(int num, int denom)
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: m_num(num)
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, m_denom(denom)
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{
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normalize();
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}
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Fraction& operator*=(int n)
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{
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m_num *= n;
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normalize();
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return *this;
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}
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Fraction& operator*=(Fraction const& other)
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{
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m_num *= other.m_num;
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m_denom *= other.m_denom;
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normalize();
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return *this;
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}
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friend Fraction operator*(Fraction f, int i) { return f *= i; }
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friend Fraction operator*(int i, Fraction const& f) { return f * i; }
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friend Fraction operator*(Fraction a, Fraction const& b) { return a *= b; }
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friend bool operator==(Fraction const& a, Fraction const& b)
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{
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return a.m_num == b.m_num && a.m_denom == b.m_denom;
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}
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friend bool operator!=(Fraction const& a, Fraction const& b) { return !(a == b); }
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friend bool operator<(Fraction const& a, Fraction const& b)
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{
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return a.m_num * b.m_denom < b.m_num * a.m_denom;
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}
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friend bool operator>(Fraction const& a, Fraction const& b) { return b < a; }
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friend bool operator<=(Fraction const& a, Fraction const& b) { return !(a > b); }
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friend bool operator>=(Fraction const& a, Fraction const& b) { return !(a < b); }
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friend std::ostream& operator<<(std::ostream& os, Fraction const& frac)
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{
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os << "[" << frac.m_num << "," << frac.m_denom << "]";
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return os;
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}
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private:
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void normalize()
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{
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const int gcd = std::gcd(m_num, m_denom);
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m_num /= gcd;
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m_denom /= gcd;
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}
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unsigned int m_num, m_denom;
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};
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// TODO: operators
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void printAndCheck(std::string const & what, Fraction const & result, Fraction const & expected) {
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const bool passed = result == expected;
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std::cout << std::left << std::setw(40) << what << ": " << (passed ? "PASS" : "** FAIL **") << " " << result << "\n";
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void printAndCheck(std::string const& what, Fraction const& result, Fraction const& expected)
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{
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const bool passed = result == expected;
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std::cout << std::left << std::setw(40) << what << ": " << (passed ? "PASS" : "** FAIL **") << " " << result << "\n";
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}
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void printAndCheck(std::string const & what, bool result, bool expected) {
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const bool passed = result == expected;
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std::cout << std::left << std::setw(40) << what << ": " << (passed ? "PASS" : "** FAIL **") << " " << result << "\n";
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void printAndCheck(std::string const& what, bool result, bool expected)
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{
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const bool passed = result == expected;
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std::cout << std::left << std::setw(40) << what << ": " << (passed ? "PASS" : "** FAIL **") << " " << result << "\n";
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}
3078

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int main() {
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// create a fraction with values 3 (which is 3/1) and 1/3
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const Fraction three{3};
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const Fraction athird{1, 3};
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// print the fractions
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std::cout << "Three: " << three << '\n';
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std::cout << "One third: " << athird << '\n';
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// multiply fraction with an int
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// the printAndCheck function requires operator<< and operator==:
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printAndCheck("One third times two", athird * 2, Fraction{2, 3});
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// ensure symmetry
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printAndCheck("Two times one third", 2 * athird, Fraction{2, 3});
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// multiply two fractions
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printAndCheck("Three times one third", three * athird, Fraction{1, 1});
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// normalize the fraction after multiplication so the above statement
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// prints 1/1 instead of e.g. 3/3
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printAndCheck("Three times one third", 3 * athird, Fraction{1, 1});
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// multiply in place
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Fraction f = athird;
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f *= 2;
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printAndCheck("One third times two", f, Fraction{2, 3});
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f *= athird;
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printAndCheck("Two third times one third", f, Fraction{2, 9});
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// you might have some redundancy between the implementation of operator* and
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// operator*=. Can you refactor your code and implement operator* in terms of
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// operator*=?
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std::cout << std::boolalpha; // print bools as 'true' or 'false' from now on
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// more equality comparisons
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printAndCheck("One third == one third", (athird == Fraction{1, 3}), true);
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printAndCheck("One third != one forth", (athird != Fraction{1, 4}), true);
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printAndCheck("One third == two sixth", (athird == Fraction{2, 6}), true);
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printAndCheck("One third != three sixth", (athird != Fraction{3, 6}), true);
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// try to implement operator!= in terms of operator==
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// more comparisons
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const Fraction afourth{1, 4};
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printAndCheck("athird < athird", (athird < athird), false);
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printAndCheck("afourth < athird", (afourth < athird), true);
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printAndCheck("athird <= athird", (athird <= athird), true);
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printAndCheck("athird <= afourth", (athird <= afourth), false);
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printAndCheck("athird > athird", (athird > athird), false);
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printAndCheck("afourth > athird", (afourth > athird), false);
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printAndCheck("athird >= athird", (athird >= athird), true);
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printAndCheck("athird >= afourth", (athird >= afourth), true);
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// the operators <=, >= and > can typically be implemented just in terms of
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// operator<. Can you do this as well? ;)
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// take aways on operators:
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// * we can very often implement an arithemtic operator@ in terms of
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// operator@=
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// * it usually suffices to implement operator< and operator== and derive the
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// other relational operators from them. C++20 will do part of this automatically.
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int main()
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{
81+
const Fraction three { 3 };
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const Fraction athird { 1, 3 };
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84+
std::cout << "Three: " << three << '\n';
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std::cout << "One third: " << athird << '\n';
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87+
// multiply fraction with an int
88+
printAndCheck("One third times two", athird * 2, Fraction { 2, 3 });
89+
printAndCheck("Two times one third", 2 * athird, Fraction { 2, 3 });
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// multiply two fractions
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printAndCheck("Three times one third", three * athird, Fraction { 1, 1 });
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printAndCheck("Three times one third", 3 * athird, Fraction { 1, 1 });
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// multiply in place
96+
Fraction f = athird;
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f *= 2;
98+
printAndCheck("One third times two", f, Fraction { 2, 3 });
99+
100+
f *= athird;
101+
printAndCheck("Two third times one third", f, Fraction { 2, 9 });
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103+
std::cout << std::boolalpha; // print bools as 'true' or 'false' from now on
104+
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// more equality comparisons
106+
printAndCheck("One third == one third", (athird == Fraction { 1, 3 }), true);
107+
printAndCheck("One third != one forth", (athird != Fraction { 1, 4 }), true);
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printAndCheck("One third == two sixth", (athird == Fraction { 2, 6 }), true);
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printAndCheck("One third != three sixth", (athird != Fraction { 3, 6 }), true);
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// more comparisons
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const Fraction afourth { 1, 4 };
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printAndCheck("athird < athird", (athird < athird), false);
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printAndCheck("afourth < athird", (afourth < athird), true);
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printAndCheck("athird <= athird", (athird <= athird), true);
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printAndCheck("athird <= afourth", (athird <= afourth), false);
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printAndCheck("athird > athird", (athird > athird), false);
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printAndCheck("afourth > athird", (afourth > athird), false);
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printAndCheck("athird >= athird", (athird >= athird), true);
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printAndCheck("athird >= afourth", (athird >= afourth), true);
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}

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