update Chapter 4

Author: ShiqiYu

week04/Lecture04.pptx

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+#include <iostream>
+using namespace std;
+
+enum color {WHITE, BLACK, RED, GREEN, BLUE, YELLOW, NUM_COLORS};
+enum datatype {TYPE_INT8=1, TYPE_INT16=2, TYPE_INT32=4, TYPE_INT64=8};
+
+struct Point{
+    enum datatype type;
+    union {
+        std::int8_t data8[3];
+        std::int16_t data16[3];
+        std::int32_t data32[3];
+        std::int64_t data64[3];
+    };
+};
+
+size_t datawidth(struct Point pt)
+{
+    return size_t(pt.type) * 3;
+}
+
+int64_t l1norm(struct Point pt)
+{
+    int64_t result = 0;
+    switch(pt.type)
+    {
+        case (TYPE_INT8): 
+            result = abs(pt.data8[0]) + abs(pt.data8[1]) + abs(pt.data8[2]);
+            break;
+        case (TYPE_INT16): 
+            result = abs(pt.data16[0]) + abs(pt.data16[1]) + abs(pt.data16[2]);
+            break;
+        case (TYPE_INT32): 
+            result = abs(pt.data32[0]) + abs(pt.data32[1]) + abs(pt.data32[2]);
+            break;
+        case (TYPE_INT64): 
+            result = abs(pt.data64[0]) + abs(pt.data64[1]) + abs(pt.data64[2]);
+            break;
+    }
+    return result;
+}
+
+int main()
+{
+    enum color pen_color = RED;
+    pen_color = color(3); //convert int to enum
+    cout << "We have " << NUM_COLORS << " pens." << endl;
+    //pen_color += 1; //error!
+    int color_index = pen_color;
+    color_index += 1;
+    cout << "color_index = " << color_index << endl;
+
+    //declaration and initialization
+    struct Point point1 = {.type=TYPE_INT8, .data8={-2,3,4}};
+    struct Point point2 = {.type=TYPE_INT32, .data32={1,-2,3}};
+    
+    cout << "Data width = " << datawidth(point1) << endl;
+    cout << "Data width = " << datawidth(point2) << endl;
+
+    cout << "L1 norm = " << l1norm(point1) << endl;
+    cout << "L1 norm = " << l1norm(point2) << endl;
+
+
+    return 0;
+}

week04/array-illustration.xlsx

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+#include <iostream>
+#include <string>
+using namespace std;
+
+int main()
+{
+    string str = "Hello, SUSTech!";
+    for(int i = 0; i <= str.length(); i++) //no bound check
+        cout << i << ": " << str[i] << endl;
+
+    return 0;
+}

week04/examples/enum.cpp

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+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+
+typedef 
+struct _Student{
+    char name[4];
+    int born;
+    bool male; 
+} Student;
+
+int main()
+{
+    Student stu = {"Yu", 2000, true}; //initialization
+    // strcpy(stu.name, "Yu");
+    // stu.born = 2000;
+    // stu.male = true;
+
+    printf("Student %s, born in %d, gender %s\n", 
+        stu.name, 
+        stu.born, 
+        stu.male ? "male" : "female");
+
+    Student students[100];
+    students[50].born = 2002; 
+
+    return 0;
+}

week04/examples/stringelement.cpp

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+#include <iostream>
+using namespace std;
+
+struct Student1{
+    int id;
+    bool male;
+    char label;
+    float height;
+};
+
+struct Student2{
+    int id;
+    bool male;
+    float height;
+    char label;
+};
+
+int main()
+{
+    cout << "Size of Student1: " << sizeof(Student1) << endl;
+    cout << "Size of Student2: " << sizeof(Student2) << endl;
+    return 0;
+}

week04/examples/struct.c

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+#include <iostream>
+using namespace std;
+
+typedef int myint;
+typedef unsigned char vec3b[3];
+typedef struct _rgb_struct{ // name _rgb_struct can be omit
+    unsigned char r;
+    unsigned char g;
+    unsigned char b;
+}  rgb_struct;
+
+int main()
+{
+    myint num = 32;
+
+    // the following two lines are identical
+    //unsigned char color[3] = {255, 0, 255};
+    vec3b color = {255, 0, 255}; 
+    cout << hex;
+    cout << "R=" << +color[0] << ", ";
+    cout << "G=" << +color[1] << ", ";
+    cout << "B=" << +color[2] << endl;
+
+    rgb_struct rgb = {0, 255, 128};
+    cout << "R=" << +rgb.r << ", ";
+    cout << "G=" << +rgb.g << ", ";
+    cout << "B=" << +rgb.b << endl;
+
+    cout << sizeof(rgb.r) << endl;
+    cout << sizeof(+rgb.r) << endl; //why 4?
+
+    return 0;
+}

week04/examples/structpadding.cpp

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+#include <iostream>
+using namespace std;
+
+union ipv4address{
+    std::uint32_t address32;
+    std::uint8_t address8[4];
+};
+
+int main()
+{
+    union ipv4address ip;
+
+    cout << "sizeof(ip) = " << sizeof(ip) << endl;
+
+    ip.address8[3] = 127;
+    ip.address8[2] = 0;
+    ip.address8[1] = 0;
+    ip.address8[0] = 1;
+
+    cout << "The address is " ;
+    cout << +ip.address8[3] << ".";
+    cout << +ip.address8[2] << ".";
+    cout << +ip.address8[1] << ".";
+    cout << +ip.address8[0] << endl;
+
+    cout << std::hex;
+    cout << "in hex " << ip.address32 << endl;
+}