char*,string,float,int 转换-白红宇

char*,string,float,int 转换

阅读量：6965 次

发布时间：2019-06-27

本文共 1888 字，大约阅读时间需要 6 分钟。

char* 转 float：

double atof (const char* str);

/* atof example: sine calculator */#include 
     
            /* printf, fgets */#include 
      
            /* atof */#include 
       
               /* sin */int main (){  double n,m;  double pi=3.1415926535;  char buffer[256];  printf ("Enter degrees: ");  fgets (buffer,256,stdin);  n = atof (buffer);  m = sin (n*pi/180);  printf ("The sine of %f degrees is %f\n" , n, m);  return 0;}

string 转 float；

float stof (const string&  str, size_t* idx = 0);float stof (const wstring& str, size_t* idx = 0);

#include 
      
          // std::cout#include 
       
             // std::string, std::stofint main (){  std::string orbits ("686.97 365.24");  std::string::size_type sz;     // alias of size_t  float mars = std::stof (orbits,&sz);  float earth = std::stof (orbits.substr(sz));  std::cout << "One martian year takes " << (mars/earth) << " Earth years.\n";  return 0;}

相关有stoi,stod,stold,以及strtod

由数值转向string：

函数原型：

string to_string (int val);string to_string (long val);string to_string (long long val);string to_string (unsigned val);string to_string (unsigned long val);string to_string (unsigned long long val);string to_string (float val);string to_string (double val);string to_string (long double val);

举例

// to_string example#include 
      
          // std::cout#include 
       
             // std::string, std::to_stringint main (){  std::string pi = "pi is " + std::to_string(3.1415926);  std::string perfect = std::to_string(1+2+4+7+14) + " is a perfect number";  std::cout << pi << '\n';  std::cout << perfect << '\n';  return 0;}

但是在某些编译器里 to_string 不被支持。http://stackoverflow.com/questions/12975341/to-string-is-not-a-member-of-std-says-so-g

解决方法：

http://stackoverflow.com/questions/11063413/erroritoa-was-not-declared-in-this-scope

转载于:https://www.cnblogs.com/xaf-dfg/p/3699256.html

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