将字符数组转换为浮点型

Question

I'm trying to convert my character array data into float. Is it possible?

Code:

char str[5] = {'1', '2', '.', '3'}
void main(char str[])
{
    float var = (float)str[]; //error
}

This code didn't work. So I also tried using:

float var = (float) (str[0], str[1], str[2], str[3]); //output: 49

and also

float var = (float) (str[0] + str[1] + str[2] + str[3]); //output: 196

But they also did not work as expected..

My expected output should be float var = 12.3

Answer 1

Yes, using std::stof , which takes a C-string (ie a null-terminated character array) and gives you a float back (if possible):

#include <iostream>
#include <string>
#include <cassert>

int main(int argc, char* argv[])
{
   assert(argc >= 2);
   const float var = std::stof(argv[1]);
   std::cout << var << '\n';
}

// $ myProgram 12.3
// 12.3

( live demo )

^{Note that I have also corrected your main return type (which must be int ), and I've gone with a more conventional set of function arguments: though their requirements are up to the implementation, VS doesn't document any support for this unconventional variant .}

Of course, you don't need the input to be from command line:

#include <iostream>
#include <string>

int main()
{
   const std::string str = "12.3";
   // or `const std::string str   = {'1', '2', '.', '3'};
   // or `const char        str[] = {'1', '2', '.', '3', '\0'};

   const float var = std::stof(str);
   std::cout << var << '\n';
}

// $ myProgram
// 12.3

( live demo )

Answer 2

std::string str = {'1', '2', '.', '3'};
float var = std::stof(str);