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Commit 66c92b7

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chavidsponce
authored andcommitted
Review operators exercise and split a preceding classes exercise from it.
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‎exercises/ExerciseSchedule_EssentialCourse.md‎

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Day 2 - OO Exercises
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--------------------
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### Polymorphism (directory: [`polymorphism`](polymorphism), [CheatSheet](ExercisesCheatSheet.md#polymorphism-directory-polymorphism))
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### My first classes (directory: [`classes`](classes), [CheatSheet](ExercisesCheatSheet.md#classes-directory-classes))
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### Operator overloading (directory: [`operators`](operators), [CheatSheet](ExercisesCheatSheet.md#operator-overloading-directory-operators))
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### Polymorphism (directory: [`polymorphism`](polymorphism), [CheatSheet](ExercisesCheatSheet.md#polymorphism-directory-polymorphism))
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### Virtual inheritance (directory: [`virtual_inheritance`](virtual_inheritance), [CheatSheet](ExercisesCheatSheet.md#virtual-inheritance-directory-virtual_inheritance))
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‎exercises/ExercisesCheatSheet.md‎

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@@ -45,6 +45,37 @@ The idea of this exercise is to play with all kinds of possible loops and contro
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Object-orientation Exercises
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----------------------------
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### Classes (directory: [`classes`](classes))
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This exercise is about doing a basic class, not using any operator overloading. It also paves the way for object-functions, making a first algo-like class.
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You may discuss with the students:
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- pros and cons of making the constructor explicit or not,
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- pros and cons of having multiply() and equal() either as member functions,
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friend free functions or external free functions.
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- optionally, thed difference between equality and equivalence.
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NOTE: I did not find a justified need to add operator=...
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### Operator overloading (directory: [`operators`](operators))
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Here we take the class from the previous exercise, and we try to make
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anything an operator that makes sense.
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Tips and tricks:
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- When the argument of CHECK() has a comma not between parentheses, for example
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curly braces, add an additional global level of parenthesis, or CHECK() will
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think it has several arguments.
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You may discuss with the students:
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- the chaining of operator<<
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- in a set of consistent operators (such as == and !=),
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reusing versus performance.
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- object-functions.
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- for what concerns the related operators, such as * and *=,
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the choice to be made consitent reuse or performant
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specialization of each operator.
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### Polymorphism (directory: [`polymorphism`](polymorphism))
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First create a Pentagon and an Hexagon and call computePerimeter. Can be used to break the ice.
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See the new id being printed twice.
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### Operator overloading (directory: [`operators`](operators))
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This exercise is about making `main` run successfully by completing the implementation of `Fraction`.
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Implement a constructor for `Fraction` and add two integer data members for numerator and denominator.
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Comment out everything in `main` except the first two LOCs.
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This should compile now and print nothing.
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Then uncomment the `std::cout` statements and implement `operator<<` for `Fraction`.
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Compile and run.
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Proceed this way through the entire exercise.
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There are multiple possibilities to implement some operators, e.g. as members, as hidden friends, or as free functions.
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Also when and where to normalize a fraction is up to the students.
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All solutions are fine, as long as the `main` function runs successfully.
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Modern C++ Exercises
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--------------------
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‎exercises/classes/.gitignore‎

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classes classes_sol

‎exercises/classes/CMakeLists.txt‎

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# Set up the project.
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cmake_minimum_required( VERSION 3.12 )
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project( operators LANGUAGES CXX )
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# Set up the compilation environment.
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include( "${CMAKE_CURRENT_SOURCE_DIR}/../common.cmake" )
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# Create the user's executable.
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add_executable( classes "classes.cpp" )
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# Create the "solution executable".
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add_executable( classes_sol EXCLUDE_FROM_ALL "solution/classes_sol.cpp" )
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add_dependencies( solution classes_sol )

‎exercises/classes/Makefile‎

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all: classes
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solution: classes_sol
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clean:
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rm -f *o classes *~ classes_sol
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classes : classes.cpp
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${CXX} -g -std=c++17 -O0 -Wall -Wextra -L. -o $@ $<
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classes_sol : solution/classes_sol.cpp
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${CXX} -g -std=c++17 -O0 -Wall -Wextra -L. -o $@ $<

‎exercises/classes/README.md‎

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## Instructions
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STEP 1
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- Complete the class Fraction so that a Fraction can be construct from one or two integer.
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Check the first two lines of main() are working (comment out the rest)
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- Add the function equal().
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Check the second section of main() works.
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- Add the function multiply().
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Check the whole main() works.
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STEP 2
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- Replace the function printTestResult() by a class TestResultPrinter
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with a method process() that take the same arguments as before.
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Upgrade CHECK() and main().
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- Transform the WIDTH constant into a variable member of TestResultPrinter,
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which is initialized in its constructor.
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Upgrade main().
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OPTIONAL STEP 3
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- Move multiply() and compare() as friend functions within the class Fraction.
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Check main() works.
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- Remove the accessors numerator() and denominator().
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Check main() works.
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OPTIONAL STEP 4
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- Remove the systematic call to normalize().
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- Add a equivalent() method to Fraction.
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- Upgrade the tests accordingly.
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- Transform the private normalize() into a public const normalized() method
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which return the normalized fraction.
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- Add some tests to check normalized().
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‎exercises/classes/classes.cpp‎

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#include <iomanip>
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#include <iostream>
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#include <numeric>
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class Fraction {
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public:
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// ADD YOUR CODE HERE
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std::string str() const {
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std::ostringstream oss;
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oss << m_num << '/' << m_denom;
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return oss.str();
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}
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int numerator() const {
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return m_num;
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}
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int denominator() const {
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return m_denom;
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}
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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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int m_num, m_denom;
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};
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// ADD YOUR CODE HERE
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#define CHECK(print,what) print(#what, what)
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unsigned int WIDTH {20};
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void printTestResult(std::string const & what, bool passed) {
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std::cout << std::setw(WIDTH) << what << ": " << (passed ? "PASS" : "** FAIL **") << '\n';
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}
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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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std::cout<<std::endl;
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const Fraction three{3};
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const Fraction third{1, 3};
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std::cout<<three.str()<<' '<<third.str()<<'\n';
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// equality
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std::cout<<std::endl;
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CHECK(printTestResult,equal(three,three));
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CHECK(printTestResult,equal(third,third));
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CHECK(printTestResult,equal(three,Fraction{3}));
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CHECK(printTestResult,equal(three,Fraction{3, 1}));
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CHECK(printTestResult,equal(third,Fraction{1, 3}));
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CHECK(printTestResult,equal(Fraction{3},three));
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CHECK(printTestResult,equal(Fraction{1, 3},third));
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CHECK(printTestResult,equal(third,Fraction{2, 6}));
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// multiply
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std::cout<<std::endl;
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CHECK(printTestResult,equal(multiply(third,2),Fraction{2, 3}));
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CHECK(printTestResult,equal(multiply(2,third),Fraction{2, 3}));
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CHECK(printTestResult,equal(multiply(three,third),Fraction{1, 1}));
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CHECK(printTestResult,equal(multiply(3,third),1));
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// end
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std::cout<<std::endl;
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}
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‎exercises/classes/classes_sol‎

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#include <iomanip>
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#include <iostream>
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#include <sstream>
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#include <numeric>
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class Fraction {
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public:
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Fraction(int a_num, int a_denom = 1) : m_num(a_num), m_denom(a_denom) {}
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std::string str() const {
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std::ostringstream oss;
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oss << m_num << '/' << m_denom;
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return oss.str();
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}
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friend bool equal( Fraction const & lhs, Fraction const & rhs ) {
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return (lhs.m_num==rhs.m_num) && (lhs.m_denom==rhs.m_denom);
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}
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friend bool equivalent( Fraction const & lhs, Fraction const & rhs ) {
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return (lhs.m_num*rhs.m_denom==rhs.m_num*lhs.m_denom);
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}
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friend Fraction multiply( Fraction const & lhs, Fraction const & rhs ) {
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return {lhs.m_num*rhs.m_num, lhs.m_denom*rhs.m_denom};
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}
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Fraction normalized() const {
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const int gcd = std::gcd(m_num, m_denom);
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return {m_num/gcd, m_denom/gcd};
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}
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private:
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int m_num, m_denom;
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};
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class TestResultPrinter {
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public:
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TestResultPrinter( unsigned int a_width ) : m_width(a_width) {}
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void process(std::string const & what, bool passed) {
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std::cout << std::left << std::setw(m_width) << what << ": " << (passed ? "PASS" : "** FAIL **") << '\n';
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}
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private:
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unsigned int m_width;
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};
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#define CHECK(printer,what) printer.process(#what, what)
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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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std::cout<<std::endl;
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const Fraction three{3};
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const Fraction third{1, 3};
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std::cout<<three.str()<<' '<<third.str()<<'\n';
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// equality
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std::cout<<std::endl;
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TestResultPrinter p1{27};
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CHECK(p1,equal(three,three));
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CHECK(p1,equal(third,third));
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CHECK(p1,equal(three,Fraction{3}));
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CHECK(p1,equal(three,Fraction{3,1}));
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CHECK(p1,equal(third,Fraction{1,3}));
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CHECK(p1,equal(Fraction{3},three));
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CHECK(p1,equal(Fraction{1,3},third));
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// equivalence
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std::cout<<std::endl;
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TestResultPrinter p2{40};
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CHECK(p2,!equal(third,Fraction{2,6}));
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CHECK(p2,equivalent(third,Fraction{2,6}));
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CHECK(p2,equal(third,Fraction{2,6}.normalized()));
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// multiply
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std::cout<<std::endl;
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TestResultPrinter p3{48};
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CHECK(p3,equal(multiply(third,2),Fraction{2,3}));
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CHECK(p3,equal(multiply(2,third),Fraction{2,3}));
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CHECK(p3,equivalent(multiply(three,third),Fraction{1,1}));
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CHECK(p3,equivalent(multiply(3,third),1));
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// end
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std::cout<<std::endl;
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}

‎exercises/operators/.gitignore‎

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operators
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operators_sol

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