Compare versions as strings

Question

Comparing version numbers as strings is not so easy...
\"1.0.0.9\" > \"1.0.0.10\", but it\'s not correct.
The obvious way to do it properly is to parse these strings

Answer 1

First the test code:

int main()
{
    std::cout << ! ( Version("1.2")   >  Version("1.3") );
    std::cout <<   ( Version("1.2")   <  Version("1.2.3") );
    std::cout <<   ( Version("1.2")   >= Version("1") );
    std::cout << ! ( Version("1")     <= Version("0.9") );
    std::cout << ! ( Version("1.2.3") == Version("1.2.4") );
    std::cout <<   ( Version("1.2.3") == Version("1.2.3") );
}
// output is 111111

Implementation:

#include 
#include 

// Method to compare two version strings
//   v1 <  v2  -> -1
//   v1 == v2  ->  0
//   v1 >  v2  -> +1
int version_compare(std::string v1, std::string v2)
{
    size_t i=0, j=0;
    while( i < v1.length() || j < v2.length() )
    {
        int acc1=0, acc2=0;

        while (i < v1.length() && v1[i] != '.') {  acc1 = acc1 * 10 + (v1[i] - '0');  i++;  }
        while (j < v2.length() && v2[j] != '.') {  acc2 = acc2 * 10 + (v2[j] - '0');  j++;  }

        if (acc1 < acc2)  return -1;
        if (acc1 > acc2)  return +1;

        ++i;
        ++j;
    }
    return 0;
}

struct Version
{
    std::string version_string;
    Version( std::string v ) : version_string(v)
    { }
};

bool operator <  (Version u, Version v) {  return version_compare(u.version_string, v.version_string) == -1;  }
bool operator >  (Version u, Version v) {  return version_compare(u.version_string, v.version_string) == +1;  }
bool operator <= (Version u, Version v) {  return version_compare(u.version_string, v.version_string) != +1;  }
bool operator >= (Version u, Version v) {  return version_compare(u.version_string, v.version_string) != -1;  }
bool operator == (Version u, Version v) {  return version_compare(u.version_string, v.version_string) ==  0;  }

https://coliru.stacked-crooked.com/a/7c74ad2cc4dca888