Question

Found this code on one of the topic. would u mind to explain what actually the code do

Code:

string Change_me(string my_string)
{
    
    for(int i = 0; i <my_string.length(); i++)
    {
      if(isdigit(my_string[i])!=0)
      {
          if(isdigit(my_string[i+1])==0)
          {  
              my_string.insert(i+1, "v");
              //v is just an arbitary choice
              //it could be any other letter
              //but it has to be a LETTER
                 
          }    
      }    
    }
    //Changed -7*-7 case
    for ( i = 0; i <my_string.length(); i++)
    {
        if(my_string[i]=='-')
        {
            if((my_string[i-1]!='v')&&(my_string[i-1]!=')'))
            {
               my_string.replace(i,1,"y"); 
            }
        }
    } 
 

    return my_string;
}

Originally Posted by isarapearl

Found this code on one of the topic. would u mind to explain what actually the code do

What does it do? Demonstrates an attempt to access memory outside the valid range of the string object that's what:

Code:

for(int i = 0; i <my_string.length(); i++)
{
    if(isdigit(my_string[i ])!=0)
    {
        if(isdigit(my_string[i+1])==0)
        {  
            my_string.insert(i+1, "v");
            //v is just an arbitary choice
            //it could be any other letter
            //but it has to be a LETTER
        }    
    }    
}

What happens if the length of the string is 10 (valid indicies between 0 and 9 inclusive) and i is 9? The second call to isdigit attempts to access my_string[10]... which is bad.

Code:

for ( i = 0; i <my_string.length(); i++)
{
    if(my_string[i ]=='-')
    {
        if((my_string[i-1]!='v')&&(my_string[i-1]!=')'))
        {
            my_string.replace(i,1,"y"); 
        }
    }
}

What happens when i is 0? Tell me what is my_string[-1] equal to?