c++ - error: cannot convert ‘std::basic_string<char,

babag · 04-23-2008, 11:08 AM

Code:

error: cannot convert ‘std::basic_string<char, std::char_traits<char>, std::allocator<char> >’ to ‘char’ in initialization

i get the above when i try to compile this:

Code:

#include <fstream>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{
   int count = 0;

   ifstream infile("/home/babag/Documents/Scripts/ScriptVariables.txt");

   vector<string> ScriptVariables;
   string line;

   while (getline(infile, line))
   {

      ScriptVariables.push_back(line);

   }

   infile.close();

   char headerA		= 	ScriptVariables[000];

   cout << ScriptVariables[000] << endl;
   cout << headerA << endl;

   return 0;
}

with help from those here i've gotten this to read each line of
a text file to an array, ScriptVariables[n].

i now want to reassign each of these array elements to another
variable with a friendlier name. that's what i'm trying to do
with:

Code:

char headerA = ScriptVariables[000];

but it gives me the error. this is just the first of a hundred,
or so, of these ScriptVariables[n] i'll reassign to new names.

also, some should be strings, some numerical. i assume there's
a way i can differentiate or convert them when i reassign the
new names?

thanks again for all the help,
BabaG

ntubski · 04-23-2008, 01:02 PM

ScriptVariables is a vector of strings, therefore ScriptVariables[0] is a string, and you can't assign a string to a char. Try

Code:

string headerA = ScriptVariables[0];

unless you just wanted to first letter, then you could do

Code:

 char headerA = ScriptVariables[0][0];

I strongly recommend you don't write numbers with leading zeros: in C(++) those are interpreted as octal numbers.

Quote:

also, some should be strings, some numerical. i assume there's
a way i can differentiate or convert them when i reassign the
new names?

You can use atoi or stringstreams

Code:

int headerA = atoi(ScriptVariables[0].c_str());

istringstream s;
s.str(ScriptVariables[0]);
s >> headerA;

If ScriptVariables[0] happens not to be a number, atoi will return 0, which makes error detection slightly more cumbersome. With stringstream, s.fail() returns true if the string doesn't parse.

babag · 05-14-2008, 06:46 PM

thanks ntubski. been a while. out of town.

got the atoi suggestion to work for most of what i need
but ran into a problem with a fractional variable. tried

[Code:]
double GamInc = atoi(ScriptVariables[75].c_str());
[/Code]

for a line in while the value is .5

in printing this variable (GamInc) i got 0 as the
returned value instead of .5

[Code:]
cout << GamInc << endl;
[/code]

what did i do wrong here?

thanks again,
BabaG

tuxdev · 05-14-2008, 07:06 PM

atoi only returns integers, so 0.5 gets truncated down to 0. Personally, I'd use stringstreams or sscanf, with a bias towards stringstreams.

nadroj · 05-14-2008, 07:09 PM

atoi is for integers, so it only accepts +,-,0,1,...,9 (no other characters including decimals). maybe try atof

babag · 05-15-2008, 11:50 AM

tried atof since most of my input was strings and worked
with atoi. couldn't get atof to work, though.

double GamInc = atof(ScriptVariables[75]);

tried istringstreams briefly and didn't get it so moved
on to atof. will haave another look at istringstreams.
any tips on what i might have wrong with atof would be
much appreciated, though.

edit:
got atof working - found a better example online:

double GamInc = atof(ScriptVariables[75].c_str());

thanks,
BabaG