cpp practice - sorting shape

Introduction

main target to practice:

• engineering practices, including unit testing, version control, make, incremental development, test driven development

• problem solving How To Solve It

Problem: : sorting shapes A simple geometry application called geo is needed to sort shapes such as triangles, circles, rectangles and others. As a command line application, geo reads shapes from an input file, sorts the shapes by area or perimeter in increasing order or decreasing order, and write the result to an output file. For example,

geo input.txt output.txt area inc

sorts the shapes in file input.txt in increasing order by area, and writes the result to the file output.txt. And

geo input.txt output.txt perimeter dec

sorts the shapes in file input.txt in decreasing order by perimeter, and writes the result to the file output.txt.

notes

static member variable

在 class 裡把 member variable 宣告成 static，代表他是「與 class 相關連」，而不是「與物件相關連」。他獨立配置記憶體，獨立於 class 的任何物件而存在，這個 class 產生的所有物件共用使同一個 static member variable，甚至不需要有物件也能夠被使用。

因為 static member variable 不屬於任何物件，所以必須定義在外面。與一般成員變數不同，static member variable 並不是經由 constructor 初始化，而是在定義時被初始化。

static member function

static member function 跟 static member variable 一樣，獨立於物件存在。可以在沒有物件產生的狀況下被使用，所以他不能使用 this，也不能存取 class 裡的一般成員變數，當然也不能使用一般成員函式。也就是說，static member function 只能存取 static member variable。

Factory

• an object that creates other objects
  • createConvexPolygon: sort vertices, and then create polygon

C++ Template

• 將 **資料型態參數化 **的功能。
• function template

template < 樣板參數型態 樣板參數名 [, 其他樣板參數] >
原型回傳型態 函數名(參數型態 原型參數名, ...) {
    //prototype codes;
}

// normal function
int myAdd(int a, int b) {
    return a + b;
}

// function template
template <class T>
T myAdd(T a, T b)
{
    return a + b;
}

int a = 1, b = 2;
myAdd<int>(a, b);

• class template

//normal class:
class myClass {
    myClass& add(const myClass& a) {
        return *this;
    }
};

//class template:
template <class T>
class myTClass
{
    T& add(const T& a) {
        return *this;
    }
};

int main() {
    myTClass<int>  a, b;
    myTClass<double> x,y;
}

std::sort

• refer to std::sort to write our bubbleSort function
• https://en.cppreference.com/w/cpp/algorithm/sort

template< class RandomIt, class Compare >
void sort( RandomIt first, RandomIt last, Compare comp );