c++ basic details

1. int、float、double

int is a 32-bit (8 bits = 1 byte, ie 4 bytes) integer variable

float is a 32-bit (4-byte) floating-point number

double is a 64-bit floating point number (8 bytes)

2. Type conversion during assignment in C++

//1.数值赋值中的类型转换
uint8_t s = 45;
double d = s;  //正确
double d = (double)s;//两种形式都可，数值默认会进行隐式类型转换

//地址赋值中的类型转换（必须强制转换）
uint8_t* ps = &s;
double* a =  ps; //错误
double* a = (double*) ps;  //地址不会默认进行隐式类型转换，必须要前面进行强制类型转换

//C和C++中强制类型转换的两种方式
double* pTime = (double*)( &(clouddata->data[(pointBytes*p) + offset_time]));//C中强制类型转换的方式
const double* pTTime = reinterpret_cast<const double*>( &(clouddata->data[(pointBytes*p) + offset_time]));//C++中强制类型转换的方式