第4章 表达式

Posted 2021-11-23 COCO_PEAK_NOODLE

1-三目运算符的写法

int main()
{
    for (unsigned g; cin >> g; )
    {
        // conditional operators
        auto result = g > 90 ? "high pass" : g < 60 ? "fail" : g < 75 ? "low pass" : "pass";
        cout << result << endl;

        // if statements
        if (g > 90)         cout << "high pass";
        else if (g < 60)    cout << "fail";
        else if (g < 75)    cout << "low pass";
        else                cout << "pass";
        cout << endl;
    }

    return 0;
}

2-类型占用字节

int main()
{
    // by using method below only include what is needed.
    using std::cout;
    using std::endl;
    
    // void type
    cout << "void: nullptr_t\\t" << sizeof(std::nullptr_t) << " bytes" << endl << endl;
    
    // boolean type
    cout << "bool:\\t\\t" << sizeof(bool) << " bytes" << endl << endl;
    
    // charactor type
    cout << "char:\\t\\t" << sizeof(char) << " bytes" << endl;
    cout << "wchar_t:\\t" << sizeof(wchar_t) << " bytes" << endl;
    cout << "char16_t:\\t" << sizeof(char16_t) << " bytes" << endl;
    cout << "char32_t:\\t" << sizeof(char32_t) << " bytes" << endl << endl;
    
    // integers type
    cout << "short:\\t\\t" << sizeof(short) << " bytes" << endl;
    cout << "int:\\t\\t" << sizeof(int) << " bytes" << endl;
    cout << "long:\\t\\t" << sizeof(long) << " bytes" << endl;
    cout << "long long:\\t" << sizeof(long long) << " bytes" << endl << endl;
    
    // floating point type
    cout << "float:\\t\\t" << sizeof(float) << " bytes" << endl;
    cout << "double:\\t\\t" << sizeof(double) << " bytes" << endl;
    cout << "long double:\\t" << sizeof(long double) << " bytes" << endl << endl;
	
    // Fixed width integers
    cout << "int8_t:\\t\\t" << sizeof(int8_t) << " bytes" << endl;
    cout << "uint8_t:\\t" << sizeof(uint8_t) << " bytes" << endl;
    cout << "int16_t:\\t" << sizeof(int16_t) << " bytes" << endl;
    cout << "uint16_t:\\t" << sizeof(uint16_t) << " bytes" << endl;
    cout << "int32_t:\\t" << sizeof(int32_t) << " bytes" << endl;
    cout << "uint32_t:\\t" << sizeof(uint32_t) << " bytes" << endl;
    cout << "int64_t:\\t" << sizeof(int64_t) << " bytes" << endl;
    cout << "uint64_t:\\t" << sizeof(uint64_t) << " bytes" << endl;
    	
    return 0;
}

输出

void: nullptr_t 8 bytes

bool:           1 bytes

char:           1 bytes
wchar_t:        4 bytes
char16_t:       2 bytes
char32_t:       4 bytes

short:          2 bytes
int:            4 bytes
long:           8 bytes
long long:      8 bytes

float:          4 bytes
double:         8 bytes
long double:    16 bytes

int8_t:         1 bytes
uint8_t:        1 bytes
int16_t:        2 bytes
uint16_t:       2 bytes
int32_t:        4 bytes
uint32_t:       4 bytes
int64_t:        8 bytes
uint64_t:       8 bytes